MBED port of https://github.com/ys1382/filagree . The only change is adding #define MBED

Dependents:   filagree_test

Files at this revision

API Documentation at this revision

Comitter:
yusufx
Date:
Wed May 30 21:13:01 2012 +0000
Commit message:

Changed in this revision

compile.c Show annotated file Show diff for this revision Revisions of this file
compile.h Show annotated file Show diff for this revision Revisions of this file
interpret.c Show annotated file Show diff for this revision Revisions of this file
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util.c Show annotated file Show diff for this revision Revisions of this file
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variable.c Show annotated file Show diff for this revision Revisions of this file
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diff -r 000000000000 -r 1a89e28dea91 compile.c
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/compile.c	Wed May 30 21:13:01 2012 +0000
@@ -0,0 +1,1379 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdarg.h>
+#include <ctype.h>
+#include <errno.h>
+
+#include "util.h"
+#include "struct.h"
+#include "serial.h"
+#include "compile.h"
+#include "vm.h"
+#include "variable.h"
+
+#define TAG              "compile"
+#define ERROR_LEX        "Lexigraphical error"
+#define ERROR_PARSE      "Parsological error"
+#define ERROR_TOKEN      "Unknown token"
+#define QUOTE            '\''
+#define ESCAPE           '\\'
+#define ESCAPED_NEWLINE  'n'
+#define ESCAPED_TAB      't'
+#define ESCAPED_QUOTE    '\''
+
+uint32_t line;
+struct array* lex_list;
+struct map *imports = NULL;
+struct byte_array *read_file(const struct byte_array *filename);
+
+// token ///////////////////////////////////////////////////////////////////
+
+    enum Lexeme {
+        LEX_NONE,
+        LEX_IMPORT,
+        LEX_LEFT_COMMENT,
+        LEX_RIGHT_COMMENT,
+        LEX_PLUS,
+        LEX_MINUS,
+        LEX_TIMES,
+        LEX_DIVIDE,
+        LEX_MODULO,
+        LEX_AND,
+        LEX_OR,
+        LEX_NOT,
+        LEX_BAND,
+        LEX_BOR,
+        LEX_INVERSE,
+        LEX_XOR,
+        LEX_LSHIFT,
+        LEX_RSHIFT,
+        LEX_GREATER,
+        LEX_LESSER,
+        LEX_SAME,
+        LEX_SET,
+        LEX_DIFFERENT,
+        LEX_COMMA,
+        LEX_PERIOD,
+        LEX_COLON,
+        LEX_LINE_COMMENT,
+        LEX_LEFTHESIS,
+        LEX_RIGHTHESIS,
+        LEX_LEFTSQUARE,
+        LEX_RIGHTSQUARE,
+        LEX_LEFTSTACHE,
+        LEX_RIGHTSTACHE,
+        LEX_IDENTIFIER,
+        LEX_STRING,
+        LEX_INTEGER,
+        LEX_TRUE,
+        LEX_FALSE,
+        LEX_IF,
+        LEX_THEN,
+        LEX_ELSE,
+        LEX_END,
+        LEX_WHILE,
+        LEX_FOR,
+        LEX_IN,
+        LEX_WHERE,
+        LEX_FUNCTION,
+        LEX_RETURN,
+        LEX_TRY,
+        LEX_CATCH,
+        LEX_THROW,
+        LEX_DO,
+    };
+
+struct token {
+    enum Lexeme lexeme;
+    uint32_t number;
+    struct byte_array *string;
+    uint32_t at_line;
+};
+
+struct number_string lexemes[] = {
+    {LEX_IMPORT,                "import"},
+    {LEX_LEFT_COMMENT,          "/*"},
+    {LEX_RIGHT_COMMENT,         "*/"},
+    {LEX_LINE_COMMENT,          "#"},
+    {LEX_PLUS,                  "+"},
+    {LEX_MINUS,                 "-"},
+    {LEX_TIMES,                 "*"},
+    {LEX_DIVIDE,                "/"},
+    {LEX_MODULO,                "%"},
+    {LEX_BAND,                  "&"},
+    {LEX_BOR,                   "|"},
+    {LEX_INVERSE,               "~"},
+    {LEX_XOR,                   "^"},
+    {LEX_RSHIFT,                ">>"},
+    {LEX_LSHIFT,                "<<"},
+    {LEX_AND,                   "and"},
+    {LEX_OR,                    "or"},
+    {LEX_NOT,                   "not"},
+    {LEX_GREATER,               ">"},
+    {LEX_LESSER,                "<"},
+    {LEX_SAME,                  "=="},
+    {LEX_SET,                   "="},
+    {LEX_DIFFERENT,             "!="},
+    {LEX_COMMA,                 ","},
+    {LEX_PERIOD,                "."},
+    {LEX_COLON,                 ":"},
+    {LEX_LEFTHESIS,             "("},
+    {LEX_RIGHTHESIS,            ")"},
+    {LEX_LEFTSQUARE,            "["},
+    {LEX_RIGHTSQUARE,           "]"},
+    {LEX_LEFTSTACHE,            "{"},
+    {LEX_RIGHTSTACHE,           "}"},
+    {LEX_TRUE,                  "true"},
+    {LEX_FALSE,                 "false"},
+    {LEX_IF,                    "if"},
+    {LEX_THEN,                  "then"},
+    {LEX_ELSE,                  "else"},
+    {LEX_END,                   "end"},
+    {LEX_WHILE,                 "while"},
+    {LEX_FUNCTION,              "function"},
+    {LEX_FOR,                   "for"},
+    {LEX_IN,                    "in"},
+    {LEX_WHERE,                 "where"},
+    {LEX_RETURN,                "return"},
+    {LEX_TRY,                   "try"},
+    {LEX_CATCH,                 "catch"},
+    {LEX_THROW,                 "throw"},
+    {LEX_DO,                    "do"}
+};
+
+const char* lexeme_to_string(enum Lexeme lexeme)
+{
+    switch (lexeme) {
+        case LEX_IDENTIFIER:    return "id";
+        case LEX_STRING:        return "string";
+        case LEX_INTEGER:       return "number";
+        default:
+            return NUM_TO_STRING(lexemes, lexeme);
+    }
+}
+
+// display ////////////////////////////////////////////////////////////////////
+
+#ifdef DEBUG
+
+void display_token(struct token *token, int depth) {
+    assert_message(depth < 10, "kablooie!");
+    char* indent = (char*)malloc(sizeof(char)*(depth+1));
+    int i;
+    for (i=0; i<depth; i++)
+        indent[i] = '\t';
+    indent[i] = 0;
+    DEBUGPRINT("%s%d ", indent, token->lexeme);
+
+    switch (token->lexeme) {
+        case LEX_NONE:                                                break;
+        case LEX_INTEGER:    DEBUGPRINT("%u", token->number);        break;
+        case LEX_STRING:
+        case LEX_IDENTIFIER: {
+            char* s = byte_array_to_string(token->string);
+            DEBUGPRINT("%s:%s", lexeme_to_string(token->lexeme), s);
+            free(s);
+        } break;
+        case LEX_FUNCTION:
+            DEBUGPRINT("fdecl");
+            break;
+        default:
+            DEBUGPRINT("%s", lexeme_to_string(token->lexeme));
+            break;
+    }
+    DEBUGPRINT("\n");
+    free(indent);
+}
+
+void display_lex_list() {
+    int i, n = lex_list->length;
+    for (i=0; i<n; i++) {
+        DEBUGPRINT("\t%d: ", i);
+        display_token((struct token*)array_get(lex_list,i), 0);
+    }
+}
+
+#endif
+
+// lex /////////////////////////////////////////////////////////////////////
+
+struct array* lex(struct byte_array *binput);
+
+struct token *token_new(enum Lexeme lexeme, int at_line) {
+    struct token *t = (struct token*)malloc(sizeof(struct token));
+    t->lexeme = lexeme;
+    t->string = NULL;
+    t->number = 0;
+    t->at_line = line;
+    return t;
+}
+
+struct token *insert_token(enum Lexeme lexeme) {
+    struct token *token = token_new(lexeme, line);
+    array_add(lex_list, token);
+    return token;
+}
+
+int insert_token_number(const char *input, int i) {
+    struct token *token = insert_token(LEX_INTEGER);
+    token->number = atoi(&input[i]);
+    //while (isdigit(input[i++]));
+    for (; isdigit(input[i]); i++);
+    return i;
+}
+
+bool isiden(char c)
+{
+    return isalnum(c) || (c=='_');
+}
+
+bool isKeyword(int n)
+{
+    for (int c,i=0; (c = lexemes[n].chars[i]); i++)
+        if (!isalpha(c))
+            return false;
+    return true;
+}
+
+int insert_token_string(enum Lexeme lexeme, const char* input, int i)
+{
+    struct byte_array *string = byte_array_new();
+    while ((lexeme==LEX_IDENTIFIER && isiden(input[i])) ||
+           (lexeme==LEX_STRING && input[i] != QUOTE)) {
+        uint8_t c = input[i++];
+        //DEBUGPRINT("@%d c=%3d %c\n", i, c, c);
+        if (c == ESCAPE) {
+            c = input[i++];
+            switch (c) {
+                case ESCAPED_NEWLINE:    c = '\n';                        break;
+                case ESCAPED_TAB:        c = '\t';                        break;
+                case ESCAPED_QUOTE:      c = '\'';                        break;
+                default:
+                    return (VOID_INT)exit_message("unknown escape");
+            }
+        }
+        byte_array_add_byte(string, c);
+    }
+
+    int end = i + (lexeme==LEX_STRING);
+    struct token *token = token_new(lexeme, line);
+    token->string = string;
+    array_add(lex_list, token);
+    //display_token(token, 0);
+    return end;
+}
+
+int insert_lexeme(int index) {
+    struct number_string sn = lexemes[index];
+    insert_token((enum Lexeme)sn.number);
+    return strlen(sn.chars);
+}
+
+int import(const char* input, int i)
+{
+    i += strlen(lexeme_to_string(LEX_IMPORT));
+    while (isspace(input[i++]));
+    struct byte_array *path = byte_array_new();
+    while (!isspace(input[i]) && input[i]!=QUOTE)
+        byte_array_add_byte(path, input[i++]);
+    byte_array_append(path, byte_array_from_string(EXTENSION_SRC));
+
+    if (!map_has(imports, path)) {
+        map_insert(imports, path, NULL);
+        struct byte_array *imported = read_file(path);
+        lex(imported);
+    }
+
+    return i+1;
+}
+
+struct array* lex(struct byte_array *binput)
+{
+    lex_list = array_new();
+    imports = map_new();
+    int i=0,j;
+    char c;
+    line = 1;
+
+    const char* input = byte_array_to_string(binput);
+    const char* right_comment = lexeme_to_string(LEX_RIGHT_COMMENT);
+    int right_comment_len = strlen(right_comment);
+
+lexmore:
+    while (i < binput->length) {
+
+        for (j=0; j<ARRAY_LEN(lexemes); j++) {
+
+            char* lexstr = lexemes[j].chars;
+
+            if (!strncmp(&input[i], lexstr, strlen(lexstr))) {
+
+                if (isKeyword(j) && i<binput->length-1 && isalpha(input[i+strlen(lexemes[j].chars)])) {
+                    //DEBUGPRINT("%s is a keyword, %c is alpha\n", lexemes[j].chars, input[i+strlen(lexemes[j].chars)]);
+                    continue; // just an identifier
+                }
+                enum Lexeme lexeme = (enum Lexeme)lexemes[j].number;
+
+                if (lexeme == LEX_LEFT_COMMENT) { // start comment with /*
+                    while (strncmp(&input[i], right_comment, right_comment_len))
+                        if (input[i++] == '\n')
+                            line++;
+                    i += right_comment_len;
+                } else if (lexeme == LEX_LINE_COMMENT) { // start line comment with #
+                    while (input[i++] != '\n');
+                    line++;
+                } else if (lexeme == LEX_IMPORT)
+                    i = import(input, i);
+                else {
+                    //DEBUGPRINT("lexeme=%d\n",lexeme);
+                    i += insert_lexeme(j);
+                }
+                goto lexmore;
+            }
+        }
+
+        c = input[i];
+
+        if (isdigit(c))         i = insert_token_number(input,i);
+        else if (isiden(c))     i = insert_token_string(LEX_IDENTIFIER, input, i);
+        else if (c == '\n')     { line++; i++; }
+        else if (isspace(c))    i++;
+        else if (c=='\'')       i = insert_token_string(LEX_STRING, input, i+1);
+        else
+            return (struct array*)exit_message(ERROR_LEX);
+    }
+#ifdef DEBUG
+//    display_lex_list();
+#endif
+    return lex_list;
+}
+
+/* parse ///////////////////////////////////////////////////////////////////
+
+BNF:
+
+<statements> --> ( <assignment> | <fcall> | <ifthenelse> | <loop> | <rejoinder> | <iterloop> | <trycatch> | <throw> )*
+<trycatch> --> LEX_TRY <statements> LEX_CATCH <variable> <statements> LEX_END
+<throw> --> LEX_THROW <expression>
+<assignment> --> <destination>, LEX_SET <source>,
+<destination> --> <variable> | ( <expression> <member> )
+<source> --> <expression>
+
+<ifthenelse> --> IF <expression> THEN <statements>
+                  ( ELSE IF <expression> THEN <statements> )*
+                  ( ELSE <statements>)? LEX_END
+<loop> --> WHILE <expression> LEX_DO <statements> LEX_END
+
+<iterator> --> LEX_FOR LEX_IDENTIFIER LEX_IN <expression> ( LEX_WHERE <expression> )?
+<iterloop> --> <iterator> LEX_DO <statements> LEX_END
+<comprehension> --> LEX_LEFTSQUARE <expression> <iterator> LEX_RIGHTSQUARE
+
+<rejoinder> --> LEX_RETURN <source>,
+<fdecl> --> FUNCTION LEX_LEFTHESIS <variable>, LEX_RIGHTHESIS <statements> LEX_END
+<fcall> --> <expression> <call>
+<call> --> LEX_LEFTHESIS <source>, LEX_RIGHTHESIS
+
+<expression> --> <exp2> ( ( LEX_SAME | LEX_DIFFERENT | LEX_GREATER | LEX_LESSER ) <exp2> )?
+<exp2> --> <exp3> ( ( LEX_PLUS | LEX_MINUS ) <exp3> )*
+<exp3> --> <exp4> ( ( LEX_PLUS | LEX_MINUS | LEX_TIMES | LEX_DIVIDE | LEX_MODULO |
+                      LEX_BAND | LEX_BOR | LEX_XOR | LEX_LSHIFT | LEX_RSHIFT) <exp3> )*
+<exp4> --> (LEX_NOT | LEX_MINUS | LEX_INVERSE)? <exp5>
+<exp5> --> <exp6> ( <call> | <member> )*
+<exp6> --> ( LEX_LEFTTHESIS <expression> LEX_RIGHTTHESIS ) | <atom>
+<atom> -->  LEX_IDENTIFIER | <float> | <integer> | <boolean> | <table> | <comprehension> | <fdecl>
+
+<variable> --> LEX_IDENTIFIER
+<boolean> --> LEX_TRUE | LEX_FALSE
+<floater> --> LEX_INTEGER LEX_PERIOD LEX_INTEGER
+<string> --> LEX_STRING
+<table> --> LEX_LEFTSQUARE <element>, LEX_RIGHTSQUARE
+<element> --> <expression> ( LEX_COLON <expression> )?
+<member> --> ( LEX_LEFTSQUARE <expression> LEX_RIGHTSQUARE ) | ( LEX_PERIOD LEX_STRING )
+
+*///////////////////////////////////////////////////////////////////////////
+
+    enum Nonterminal {
+        SYMBOL_STATEMENTS,
+        SYMBOL_ASSIGNMENT,
+        SYMBOL_SOURCE,
+        SYMBOL_DESTINATION,
+        SYMBOL_IF_THEN_ELSE,
+        SYMBOL_LOOP,
+        SYMBOL_EXPRESSION,
+        SYMBOL_INTEGER,
+        SYMBOL_FLOAT,
+        SYMBOL_STRING,
+        SYMBOL_VARIABLE,
+        SYMBOL_TABLE,
+        SYMBOL_PAIR,
+        SYMBOL_FDECL,
+        SYMBOL_FCALL,
+        SYMBOL_MEMBER,
+        SYMBOL_RETURN,
+        SYMBOL_BOOLEAN,
+        SYMBOL_NIL,
+        SYMBOL_ITERATOR,
+        SYMBOL_ITERLOOP,
+        SYMBOL_COMPREHENSION,
+        SYMBOL_TRYCATCH,
+        SYMBOL_THROW,
+    } nonterminal;
+
+struct symbol {
+    enum Nonterminal nonterminal;
+    const struct token *token;
+    struct array* list;
+    struct symbol *index, *value;
+    float floater;
+    bool lhs;
+};
+
+struct number_string nonterminals[] = {
+    {SYMBOL_STATEMENTS,     "statements"},
+    {SYMBOL_ASSIGNMENT,     "assignment"},
+    {SYMBOL_SOURCE,         "source"},
+    {SYMBOL_DESTINATION,    "destination"},
+    {SYMBOL_IF_THEN_ELSE,   "if-then-else"},
+    {SYMBOL_LOOP,           "loop"},
+    {SYMBOL_EXPRESSION,     "expression"},
+    {SYMBOL_INTEGER,        "integer"},
+    {SYMBOL_FLOAT,          "float"},
+    {SYMBOL_STRING,         "string"},
+    {SYMBOL_VARIABLE,       "variable"},
+    {SYMBOL_TABLE,          "table"},
+    {SYMBOL_PAIR,           "pair"},
+    {SYMBOL_FDECL,          "fdecl"},
+    {SYMBOL_FCALL,          "fcall"},
+    {SYMBOL_MEMBER,         "member"},
+    {SYMBOL_RETURN,         "return"},
+    {SYMBOL_BOOLEAN,        "boolean"},
+    {SYMBOL_NIL,            "nil"},
+    {SYMBOL_ITERATOR,       "iterator"},
+    {SYMBOL_ITERLOOP,       "iterloop"},
+    {SYMBOL_COMPREHENSION,  "comprehension"},
+    {SYMBOL_TRYCATCH,       "try-catch"},
+    {SYMBOL_THROW,          "throw"},
+};
+
+struct array* parse_list;
+uint32_t parse_index;
+struct symbol *expression();
+struct symbol *statements();
+struct symbol *comprehension();
+
+struct symbol *symbol_new(enum Nonterminal nonterminal)
+{
+    //    DEBUGPRINT("symbol_new %s\n", NUM_TO_STRING(nonterminals, ARRAY_LEN(nonterminals), nonterminal));
+    struct symbol *s = (struct symbol*)malloc(sizeof(struct symbol));
+    s->nonterminal = nonterminal;
+    s->list = array_new();
+    s->index = s->value = NULL;
+    s->lhs = false;
+    return s;
+}
+
+struct symbol *symbol_add(struct symbol *s, struct symbol *t)
+{
+    null_check(s);
+    if (!t)
+        return NULL;
+    //DEBUGPRINT("symbol_add %s\n", nonterminals[t->nonterminal]);
+    array_add(s->list, t);
+    return s;
+}
+
+#ifdef DEBUG
+
+void display_symbol(const struct symbol *symbol, int depth)
+{
+    //    null_check(symbol);
+    if (!symbol)
+        return;
+    assert_message(depth < 100, "kablooie!");
+    char* indent = (char*)malloc(sizeof(char)*(depth+1));
+    int i;
+    for (i=0; i<depth; i++)
+        indent[i] = '\t';
+    indent[i] = 0;
+    DEBUGPRINT("%s%d %s", indent, symbol->nonterminal, NUM_TO_STRING(nonterminals, symbol->nonterminal));
+
+    switch (symbol->nonterminal) {
+        case SYMBOL_INTEGER:
+            DEBUGPRINT(": %u\n", symbol->token->number);
+            break;
+        case SYMBOL_FLOAT:
+            DEBUGPRINT(": %f\n", symbol->floater);
+            break;
+        case SYMBOL_VARIABLE: {
+            char* s = byte_array_to_string(symbol->token->string);
+            DEBUGPRINT(": '%s (%s)'\n", s, symbol->lhs ? "lhs":"rhs");
+            free(s);
+        } break;
+        case SYMBOL_STRING: {
+            char* s = byte_array_to_string(symbol->token->string);
+            DEBUGPRINT(": '%s'\n", s);
+            free(s);
+        } break;
+        case SYMBOL_EXPRESSION:
+            DEBUGPRINT(" %s\n", lexeme_to_string(symbol->token->lexeme));
+            break;
+        case SYMBOL_TRYCATCH:
+            DEBUGPRINT("try\n");
+            display_symbol(symbol->index, depth);
+            DEBUGPRINT("catch %s\n", byte_array_to_string(symbol->token->string));
+            display_symbol(symbol->value, depth);
+            break;
+        default:
+            DEBUGPRINT("\n");
+            depth++;
+            display_symbol(symbol->index, depth);
+            display_symbol(symbol->value, depth);
+            depth--;
+            break;
+    }
+
+    const struct array *list = symbol->list;
+    if (list && list->length) {
+        DEBUGPRINT("%s\tlist:\n", indent);
+        depth++;
+        for (int k=0; k<list->length; k++) {
+            const struct symbol *item = array_get(list, k);
+            display_symbol(item, depth);
+        }
+    }
+
+    free(indent);
+}
+
+#endif
+
+#define LOOKAHEAD (lookahead(0))
+#define FETCH_OR_QUIT(x) if (!fetch(x)) return NULL;
+#define OR_ERROR(x) { exit_message("missing %s at line %d", NUM_TO_STRING(lexemes, x), line); return NULL; }
+#define FETCH_OR_ERROR(x) if (!fetch(x)) OR_ERROR(x);
+
+
+enum Lexeme lookahead(int n) {
+    if (parse_index + n >= parse_list->length)
+        return LEX_NONE;
+    struct token *token = (struct token*)parse_list->data[parse_index+n];
+    assert_message(token!=0, ERROR_NULL);
+    return token->lexeme;
+}
+
+struct token *fetch(enum Lexeme lexeme) {
+    if (parse_index >= parse_list->length)
+        return NULL;
+    struct token *token = (struct token*)parse_list->data[parse_index];
+    if (token->lexeme != lexeme) {
+        //DEBUGPRINT("fetched %s instead of %s at %d\n", lexeme_to_string(token->lexeme), lexeme_to_string(lexeme), parse_index);
+        return NULL;
+    }
+    //DEBUGPRINT("fetched %s at %d\n", lexeme_to_string(lexeme), parse_index);
+    //  display_token(token, 0);
+
+    parse_index++;
+    return token;
+}
+
+typedef struct symbol*(Parsnip)();
+
+struct symbol *one_of(Parsnip *p, ...) {
+    uint32_t start = parse_index;
+    struct symbol *t = NULL;
+    va_list argp;
+    va_start(argp, p);
+    for (;
+         p && !(t=p());
+         p = va_arg(argp, Parsnip*))
+        parse_index=start;
+    va_end(argp);
+    return t;
+}
+
+struct token *fetch_lookahead(enum Lexeme lexeme, ...) {
+    struct token *t=NULL;
+    va_list argp;
+    va_start(argp, lexeme);
+
+    for (; lexeme; lexeme = (enum Lexeme)va_arg(argp, int)) {
+        if (LOOKAHEAD == lexeme) {
+            t = fetch(lexeme);
+            break;
+        }
+    }
+    va_end(argp);
+    return t;
+}
+
+struct symbol *symbol_fetch(enum Nonterminal n, enum Lexeme goal, ...)
+{
+    if (parse_index >= parse_list->length)
+        return NULL;
+    struct token *token = (struct token*)parse_list->data[parse_index];
+    assert_message(token!=0, ERROR_NULL);
+    enum Lexeme lexeme = token->lexeme;
+
+    struct symbol *symbol = NULL;
+
+    va_list argp;
+    va_start(argp, goal);
+
+    for (; goal; goal = (enum Lexeme)va_arg(argp, int)) {
+        if (lexeme == goal) {
+
+            symbol = symbol_new(n);
+            symbol->token = token;
+            // DEBUGPRINT("fetched %s at %d\n", lexeme_to_string(lexeme), parse_index);
+            // display_token(token, 0);
+
+            parse_index++;
+            break;
+        }
+    }
+    va_end(argp);
+    return symbol;
+}
+
+struct symbol *symbol_adds(struct symbol *s, struct symbol *child, ...) {
+    va_list argp;
+    va_start(argp, child);
+    for (; child; child = va_arg(argp, struct symbol*))
+        array_add(s->list, child);
+    va_end(argp);
+    return s;
+
+}
+
+// <x>, --> ( <x> ( LEX_COMMA <x> )* )?
+// e.g. a list of zero or more <x>, separated by commas
+struct symbol *repeated(enum Nonterminal nonterminal, Parsnip *p)
+{
+    struct symbol *r, *s = symbol_new(nonterminal);
+    do {
+        if (!(r=p()))
+            break;
+        symbol_add(s, r);
+    } while (fetch(LEX_COMMA));
+    return s;
+}
+
+//////////////////////////////// BNFs
+
+
+// <destination> --> <variable> | ( <expression> <member> )
+struct symbol *destination()
+{
+    struct symbol *e = expression();
+    if (!e ||
+        (e->nonterminal != SYMBOL_MEMBER &&
+         e->nonterminal != SYMBOL_VARIABLE))
+        return NULL;
+    e->lhs = true;
+    return e;
+};
+
+//<variable> --> LEX_IDENTIFIER
+struct symbol *variable()
+{
+    return symbol_fetch(SYMBOL_VARIABLE, LEX_IDENTIFIER, NULL);
+}
+
+
+// <fdecl> --> FUNCTION LEX_LEFTHESIS <variable>, LEX_RIGHTHESIS <statements> LEX_END
+struct symbol *fdecl()
+{
+    FETCH_OR_QUIT(LEX_FUNCTION)
+    FETCH_OR_ERROR(LEX_LEFTHESIS);
+    struct symbol *s = symbol_new(SYMBOL_FDECL);
+    s->index = repeated(SYMBOL_DESTINATION, &destination);
+    FETCH_OR_ERROR(LEX_RIGHTHESIS)
+    s->value = statements();
+    //DEBUGPRINT("fdecl: %d statements\n", s->value->list->length);
+    //DEBUGPRINT("lookahead=%s\n", NUM_TO_STRING(lexemes, LOOKAHEAD));
+    FETCH_OR_ERROR(LEX_END);
+    return s;
+}
+
+// <element> --> <expression> ( LEX_COLON <expression> )?
+struct symbol *element()
+{
+    struct symbol *e = expression();
+    if (fetch(LEX_COLON)) { // i.e. x:y
+        struct symbol *p = symbol_new(SYMBOL_PAIR);
+        p->index = e;
+        p->value = expression();
+        return p;
+    } else {
+//        p->index = symbol_new(SYMBOL_NIL);
+        return e;
+    }
+}
+
+// <table> --> LEX_LEFTSQUARE <element>, LEX_RIGHTSQUARE
+struct symbol *table() {
+    //return list(SYMBOL_TABLE, LEX_LEFTSQUARE, LEX_RIGHTSQUARE, LEX_COLON);
+    FETCH_OR_QUIT(LEX_LEFTSQUARE);
+    struct symbol *s = repeated(SYMBOL_TABLE, &element);
+    FETCH_OR_ERROR(LEX_RIGHTSQUARE);
+    return s;
+}
+
+struct symbol *integer()
+{
+    //    DEBUGPRINT("integer\n");
+    struct token *t = fetch(LEX_INTEGER);
+    if (!t)
+        return NULL;
+    struct symbol *s = symbol_new(SYMBOL_INTEGER);
+    s->token = t;
+    return s;
+}
+
+struct symbol *boolean()
+{
+    struct token *t = fetch_lookahead(LEX_TRUE, LEX_FALSE, NULL);
+    if (!t)
+        return NULL;
+    struct symbol *s = symbol_new(SYMBOL_BOOLEAN);
+    s->token = t;
+    return s;
+}
+
+struct symbol *floater()
+{
+    //    DEBUGPRINT("floater\n");
+    struct token *t = fetch(LEX_INTEGER);
+    if (!t)
+        return NULL;
+    FETCH_OR_QUIT(LEX_PERIOD);
+    struct token *u = fetch(LEX_INTEGER);
+
+    float decimal = u->number;
+    while (decimal > 1)
+        decimal /= 10;
+
+    struct symbol *s = symbol_new(SYMBOL_FLOAT);
+    s->floater = t->number + decimal;
+    return s;
+}
+
+// <string> --> LEX_STRING
+struct symbol *string()
+{
+    struct token *t = fetch(LEX_STRING);
+    if (!t)
+        return NULL;
+    struct symbol *s = symbol_new(SYMBOL_STRING);
+    s->token = t;
+    return s;
+}
+
+//  <atom> -->  LEX_IDENTIFIER | <float> | <integer> | <boolean> | <table> | <comprehension> | <fdecl>
+struct symbol *atom()
+{
+    return one_of(&variable, &string, &floater, &integer, &boolean, &comprehension, &table, &fdecl, NULL);
+}
+
+// <exp5> --> ( LEX_LEFTTHESIS <expression> LEX_RIGHTTHESIS ) | <atom>
+struct symbol *exp5()
+{
+    if (fetch(LEX_LEFTHESIS)) {
+        struct symbol *s = expression();
+        fetch(LEX_RIGHTHESIS);
+        return s;
+    }
+    return atom();
+}
+
+// <member> --> ( LEX_LEFTSQUARE <expression> LEX_RIGHTSQUARE ) | ( LEX_PERIOD LEX_STRING )
+struct symbol *member()
+{
+    struct symbol *m = symbol_new(SYMBOL_MEMBER);
+
+    if (fetch(LEX_PERIOD)) {
+        m->index = variable();
+        m->index->nonterminal = SYMBOL_STRING;
+    }
+    else {
+        FETCH_OR_QUIT(LEX_LEFTSQUARE);
+        m->index = expression();
+        FETCH_OR_QUIT(LEX_RIGHTSQUARE);
+    }
+    return m;
+}
+
+// <call> --> LEX_LEFTHESIS <source>, LEX_RIGHTHESIS
+struct symbol *call()
+{
+    struct symbol *s = symbol_new(SYMBOL_FCALL);
+    FETCH_OR_QUIT(LEX_LEFTHESIS);
+    s->index = repeated(SYMBOL_SOURCE, &expression); // arguments
+    FETCH_OR_ERROR(LEX_RIGHTHESIS);
+    return s;
+}
+
+// <fcall> --> <expression> <call>
+struct symbol *fcall()
+{
+    struct symbol *e = expression();
+    return (e && e->nonterminal ==  SYMBOL_FCALL) ? e : NULL;
+}
+
+// <exp4> --> <exp5> ( <call> | member )*
+struct symbol *exp4()
+{
+    struct symbol *g, *f;
+    f = exp5();
+    while (f && (g = one_of(&call, &member, NULL))) {
+        g->value = f;
+        f = g;
+    }
+    return f;
+}
+
+// <exp3> --> (NOT | LEX_MINUS)? <exp4>
+struct symbol *exp3()
+{
+    struct symbol *e;
+    if ((e = symbol_fetch(SYMBOL_EXPRESSION, LEX_MINUS, LEX_NOT, NULL)))
+        return symbol_add(e, exp3());
+    return exp4();
+}
+
+// <exp2> --> (<exp3> ( ( LEX_PLUS | LEX_MINUS | LEX_TIMES | LEX_DIVIDE | MODULO ))* <exp3>
+struct symbol *expTwo()
+{
+    struct symbol *e, *f;
+    e = exp3();
+    while ((f = symbol_fetch(SYMBOL_EXPRESSION, LEX_PLUS, LEX_MINUS, LEX_TIMES, LEX_DIVIDE, LEX_MODULO, NULL)))
+        e = symbol_adds(f, e, exp3(), NULL);
+    return e;
+}
+
+// <expression> --> <exp2> ( ( LEX_SAME | LEX_DIFFERENT | LEX_GREATER | LEX_LESSER ) <exp2> )?
+struct symbol *expression()
+{
+    struct symbol *f, *e = expTwo();
+    while ((f = symbol_fetch(SYMBOL_EXPRESSION, LEX_SAME, LEX_DIFFERENT, LEX_GREATER, LEX_LESSER, NULL)))
+        e = symbol_adds(f, e, expTwo(), NULL);
+    return e;
+}
+
+// <assignment> --> <destination>, LEX_SET <source>,
+struct symbol *assignment()
+{
+    struct symbol *d = repeated(SYMBOL_DESTINATION, &destination);
+    FETCH_OR_QUIT(LEX_SET);
+    struct symbol *s = symbol_new(SYMBOL_ASSIGNMENT);
+    s->value = repeated(SYMBOL_SOURCE, expression);
+    s->index = d;
+    return s;
+}
+
+/*    <ifthenelse> --> IF <expression>
+                        THEN <statements>
+                        (ELSE IF <expression> THEN <statements>)*
+                        (ELSE <statements>)?
+                     END */
+struct symbol *ifthenelse()
+{
+    FETCH_OR_QUIT(LEX_IF);
+    struct symbol *f = symbol_new(SYMBOL_IF_THEN_ELSE);
+    symbol_add(f, expression());
+    fetch(LEX_THEN);
+    symbol_add(f, statements());
+
+    while (lookahead(0) == LEX_ELSE && lookahead(1) == LEX_IF) {
+        fetch(LEX_ELSE);
+        fetch(LEX_IF);
+        symbol_add(f, expression());
+        fetch(LEX_THEN);
+        symbol_add(f, statements());
+    }
+
+    if (fetch_lookahead(LEX_ELSE))
+        symbol_add(f, statements());
+    fetch(LEX_END);
+    return f;
+}
+
+// <loop> --> WHILE <expression> <statements> END
+struct symbol *loop()
+{
+    FETCH_OR_QUIT(LEX_WHILE);
+    struct symbol *s = symbol_new(SYMBOL_LOOP);
+    s->index = expression();
+    s->value = statements();
+    FETCH_OR_ERROR(LEX_END);
+    return s;
+}
+
+// <iterator> --> LEX_FOR LEX_IDENTIFIER LEX_IN <expression> ( LEX_WHERE <expression> )?
+struct symbol *iterator()
+{
+    FETCH_OR_QUIT(LEX_FOR);
+    const struct token *t = fetch(LEX_IDENTIFIER);
+    struct symbol *s = symbol_new(SYMBOL_ITERATOR);
+    s->token = t;
+
+    FETCH_OR_ERROR(LEX_IN);
+    s->value = expression();
+    if (fetch_lookahead(LEX_WHERE))
+        s->index = expression();
+    return s;
+}
+
+// <comprehension> --> LEX_LEFTSQUARE <expression> <iterator> LEX_RIGHTSQUARE
+struct symbol *comprehension()
+{
+    //    DEBUGPRINT("comprehension\n");
+    FETCH_OR_QUIT(LEX_LEFTSQUARE);
+    struct symbol *s = symbol_new(SYMBOL_COMPREHENSION);
+    s->value = expression();
+    s->index = iterator();
+    if (!s->index)
+        return NULL;
+    FETCH_OR_ERROR(LEX_RIGHTSQUARE);
+    return s;
+}
+
+// <iterloop> --> <iterator> <statements> LEX_END
+struct symbol *iterloop()
+{
+    struct symbol *i = iterator();
+    if (!i)
+        return  NULL;
+    struct symbol *s = symbol_new(SYMBOL_ITERLOOP);
+    s->index = i;
+    s->value = statements();
+    FETCH_OR_ERROR(LEX_END);
+    return s;
+}
+
+// <rejoinder> --> // LEX_RETURN <expression>
+struct symbol *rejoinder()
+{
+    FETCH_OR_QUIT(LEX_RETURN);
+    return repeated(SYMBOL_RETURN, &expression); // return values
+}
+
+// <trycatch> --> LEX_TRY <statements> LEX_CATCH <destination> <statements> LEX_END
+struct symbol *trycatch()
+{
+    FETCH_OR_QUIT(LEX_TRY);
+    struct symbol *s = symbol_new(SYMBOL_TRYCATCH);
+    s->index = statements();
+    FETCH_OR_ERROR(LEX_CATCH);
+    if (!(s->token = fetch(LEX_IDENTIFIER)))
+        OR_ERROR(LEX_IDENTIFIER);
+    s->lhs = true;
+    s->value = statements();
+    FETCH_OR_ERROR(LEX_END);
+    return s;
+}
+
+// <throw> --> LEX_THROW <expression>
+struct symbol *thrower()
+{
+    FETCH_OR_QUIT(LEX_THROW);
+    struct symbol *s = symbol_new(SYMBOL_THROW);
+    s->value = expression();
+    return s;
+}
+
+struct symbol *strings_and_variables()
+{
+    struct array *sav = array_new();
+    while ((array_add(sav, variable()) || array_add(sav, string())));
+    return (struct symbol*)sav;
+}
+
+// <statements> --> ( <assignment> | <fcall> | <ifthenelse> | <loop> | <rejoinder> | <iterloop> ) *
+struct symbol *statements()
+{
+    struct symbol *s = symbol_new(SYMBOL_STATEMENTS);
+    struct symbol *t;
+    while ((t = one_of(&assignment, &fcall, &ifthenelse, &loop, &rejoinder, &iterloop, &trycatch, &thrower, NULL)))
+        symbol_add(s, t);
+    return s;
+}
+
+struct symbol *parse(struct array *list, uint32_t index)
+{
+    DEBUGPRINT("parse:\n");
+    assert_message(list!=0, ERROR_NULL);
+    assert_message(index<list->length, ERROR_INDEX);
+
+    parse_list = list;
+    parse_index = index;
+
+    struct symbol *p = statements();
+#ifdef DEBUG
+    display_symbol(p, 1);
+#endif
+    return p;
+}
+
+
+// generate ////////////////////////////////////////////////////////////////
+
+struct byte_array *generate_code(struct byte_array *code, struct symbol *root);
+
+void generate_step(struct byte_array *code, int count, int action,...)
+{
+    byte_array_add_byte(code, action);
+
+    va_list argp;
+    uint8_t parameter;
+    for(va_start(argp, action); --count;) {
+        parameter = va_arg(argp, int);
+        byte_array_add_byte(code, (uint8_t)parameter);
+    }
+    va_end(argp);
+}
+
+void generate_items(struct byte_array *code, const struct symbol* root)
+{
+    const struct array *items = root->list;
+    uint32_t num_items = items->length;
+
+    for (int i=0; i<num_items; i++) {
+        struct symbol *item = (struct symbol*)array_get(items, i);
+        generate_code(code, item);
+    }
+}
+
+void generate_items_then_op(struct byte_array *code, enum Opcode opcode, const struct symbol* root)
+{
+    generate_items(code, root);
+    generate_step(code, 1, opcode);
+    serial_encode_int(code, 0, root->list->length);
+}
+
+void generate_statements(struct byte_array *code, struct symbol *root) {
+    if (root)
+        generate_items(code, root);
+}
+
+void generate_return(struct byte_array *code, struct symbol *root) {
+    generate_items_then_op(code, VM_RET, root);
+}
+
+void generate_nil(struct byte_array *code, struct symbol *root) {
+    generate_step(code, 1, VM_NIL);
+}
+
+static void generate_jump(struct byte_array *code, int32_t offset) {
+    generate_step(code, 1, VM_JMP);
+    serial_encode_int(code, 0, offset);
+}
+
+void generate_list(struct byte_array *code, struct symbol *root) {
+    generate_items_then_op(code, VM_LST, root);
+}
+
+void generate_float(struct byte_array *code, struct symbol *root)
+{
+    generate_step(code, 1, VM_FLT);
+    serial_encode_float(code, 0, root->floater);
+}
+
+void generate_integer(struct byte_array *code, struct symbol *root) {
+    generate_step(code, 1, VM_INT);
+    serial_encode_int(code, 0, root->token->number);
+}
+
+void generate_string(struct byte_array *code, struct symbol *root) {
+    generate_step(code, 1, VM_STR);
+    serial_encode_string(code, 0, root->token->string);
+}
+
+void generate_source(struct byte_array *code, struct symbol *root) {
+    generate_items_then_op(code, VM_SRC, root);
+}
+
+void generate_destination(struct byte_array *code, struct symbol *root)
+{
+    generate_items(code, root);
+    generate_step(code, 1, VM_DST);
+}
+
+void generate_assignment(struct byte_array *code, struct symbol *root)
+{
+    generate_code(code, root->value);
+    generate_code(code, root->index);
+}
+
+void generate_variable(struct byte_array *code, struct symbol *root)
+{
+    generate_step(code, 1, root->lhs ? VM_SET : VM_VAR);
+    serial_encode_string(code, 0, root->token->string);
+}
+
+void generate_boolean(struct byte_array *code, struct symbol *root) {
+    uint32_t value = 0;
+    switch (root->token->lexeme) {
+        case        LEX_TRUE:  value = 1;               break;
+        case        LEX_FALSE: value = 0;               break;
+        default:    exit_message("bad boolean value");    return;
+    }
+    generate_step(code, 1, VM_BOOL);
+    serial_encode_int(code, 0, value);
+}
+
+void generate_fdecl(struct byte_array *code, struct symbol *root)
+{
+    struct byte_array *f = byte_array_new();
+    generate_code(f, root->index);
+    generate_code(f, root->value);
+    generate_step(code, 1, VM_FNC);
+    serial_encode_string(code, 0, f);
+}
+
+void generate_pair(struct byte_array *code, struct symbol *root)
+{
+    generate_code(code, root->index);
+    generate_code(code, root->value);
+    generate_step(code, 2, VM_MAP, 1);
+}
+
+void generate_member(struct byte_array *code, struct symbol *root)
+{
+    generate_code(code, root->index); // array_get(root->branches, INDEX));
+    generate_code(code, root->value); // array_get(root->branches, ITERABLE));
+
+    enum Opcode op = root->lhs ? VM_PUT : VM_GET;
+    generate_step(code, 1, op);
+}
+
+void generate_fcall(struct byte_array *code, struct symbol *root)
+{
+    generate_code(code, root->index); // arguments
+
+    if (root->value->nonterminal == SYMBOL_MEMBER) {
+        generate_code(code, root->value->index);
+        generate_code(code, root->value->value);
+        generate_step(code, 1, VM_MET);
+    } else {
+        generate_code(code, root->value); // function
+        generate_step(code, 1, VM_CAL);    
+    }
+}
+
+void generate_math(struct byte_array *code, struct symbol *root)
+{
+    enum Lexeme lexeme = root->token->lexeme;
+    generate_statements(code, root);
+    enum Opcode op = VM_NIL;
+    switch (lexeme) {
+        case LEX_PLUS:      op = VM_ADD;            break;
+        case LEX_MINUS:     op = VM_SUB;            break;
+        case LEX_TIMES:     op = VM_MUL;            break;
+        case LEX_DIVIDE:    op = VM_DIV;            break;
+        case LEX_MODULO:    op = VM_MOD;            break;
+        case LEX_AND:       op = VM_AND;            break;
+        case LEX_OR:        op = VM_OR;             break;
+        case LEX_NOT:       op = VM_NOT;            break;
+        case LEX_SAME:      op = VM_EQU;            break;
+        case LEX_DIFFERENT: op = VM_NEQ;            break;
+        case LEX_GREATER:   op = VM_GTN;            break;
+        case LEX_LESSER:    op = VM_LTN;            break;
+        default: exit_message("bad math lexeme");   break;
+    }
+    generate_step(code, 1, op);
+}
+
+void generate_ifthenelse(struct byte_array *code, struct symbol *root)
+{
+    struct array *gotos = array_new(); // for skipping to end of elseifs, if one is true
+
+    for (int i=0; i<root->list->length; i+=2) {
+    
+        // then
+        struct symbol *thn = (struct symbol*)array_get(root->list, i+1);
+        assert_message(thn->nonterminal == SYMBOL_STATEMENTS, "branch syntax error");
+        struct byte_array *thn_code = byte_array_new();
+        generate_code(thn_code, thn);
+        generate_jump(thn_code, 0); // jump to end
+    
+        // if
+        struct symbol *iff = (struct symbol*)array_get(root->list, i);
+        generate_code(code, iff);
+        generate_step(code, 2, VM_IFF, thn_code->length);
+        byte_array_append(code, thn_code);
+        array_add(gotos, (void*)(VOID_INT)(code->length-1));
+    
+        // else
+        if (root->list->length > i+2) {
+            struct symbol *els = (struct symbol*)array_get(root->list, i+2);
+            if (els->nonterminal == SYMBOL_STATEMENTS) {
+                assert_message(root->list->length == i+3, "else should be the last branch");
+                generate_code(code, els);
+                break;
+            }
+        }
+    }
+
+    // go back and fill in where to jump to the end of if-then-elseif-else when done
+    for (int j=0; j<gotos->length; j++) {
+        VOID_INT g = (VOID_INT)array_get(gotos, j);
+        code->data[g] = code->length - g;
+    }
+}
+
+void generate_loop(struct byte_array *code, struct symbol *root)
+{
+    struct byte_array *ifa = byte_array_new();
+    generate_code(ifa, root->index);
+
+    struct byte_array *b = byte_array_new();
+    generate_code(b, root->value);
+
+    struct byte_array *thn = byte_array_new();
+    generate_step(thn, 1, VM_IFF);
+    serial_encode_int(thn, 0, b->length + 2);
+
+    struct byte_array *while_a_do_b = byte_array_concatenate(4, code, ifa, thn, b);
+    byte_array_append(code, while_a_do_b);
+    int32_t loop_length = ifa->length + thn->length + b->length;
+    generate_jump(code, -loop_length-1);
+}
+
+// <iterator> --> LEX_FOR LEX_IDENTIFIER LEX_IN <expression> ( LEX_WHERE <expression> )?
+void generate_iterator(struct byte_array *code, struct symbol *root, enum Opcode op)
+{
+    struct symbol *ator = root->index;
+    generate_code(code, ator->value);                   //    IN b
+    generate_step(code, 1, op);                         //    iterator or comprehension
+    serial_encode_string(code, 0, ator->token->string); // FOR a
+
+    if (ator->index) {                                  // WHERE c
+        struct byte_array *where = byte_array_new();
+        generate_code(where, ator->index);
+        serial_encode_string(code, 0, where);
+    }
+    else
+        generate_nil(code, NULL);
+
+    struct byte_array *what = byte_array_new();
+    generate_code(what, root->value);
+    serial_encode_string(code, 0, what);    // DO d
+}
+
+// <iterloop> --> <iterator> <statements> LEX_END
+void generate_iterloop(struct byte_array *code, struct symbol *root) {
+    generate_iterator(code, root, VM_ITR);
+}
+
+// <comprehension> --> LEX_LEFTSQUARE <expression> <iterator> LEX_RIGHTSQUARE
+void generate_comprehension(struct byte_array *code, struct symbol *root) {
+    generate_iterator(code, root, VM_COM);
+}
+
+// <trycatch> --> LEX_TRY <statements> LEX_CATCH <variable> <statements> LEX_END
+void generate_trycatch(struct byte_array *code, struct symbol *root)
+{
+    struct byte_array *trial = generate_code(NULL, root->index);
+
+    generate_step(code, 1, VM_TRY);
+    serial_encode_string(code, 0, trial);
+
+    serial_encode_string(code, 0, root->token->string);
+    struct byte_array *catcher = generate_code(NULL, root->value);
+    serial_encode_string(code, 0, catcher);
+}
+
+void generate_throw(struct byte_array *code, struct symbol *root)
+{
+    generate_code(code, root->value);
+    generate_step(code, 1, VM_TRO);
+}
+
+typedef void(generator)(struct byte_array*, struct symbol*);
+
+struct byte_array *generate_code(struct byte_array *code, struct symbol *root)
+{
+    if (!root)
+        return NULL;
+    generator *g = NULL;
+
+    //DEBUGPRINT("generate_code %s\n", nonterminals[root->nonterminal]);
+    switch(root->nonterminal) {
+        case SYMBOL_NIL:            g = generate_nil;           break;
+        case SYMBOL_PAIR:           g = generate_pair;          break;
+        case SYMBOL_LOOP:           g = generate_loop;          break;
+        case SYMBOL_FDECL:          g = generate_fdecl;         break;
+        case SYMBOL_TABLE:          g = generate_list;          break;
+        case SYMBOL_FCALL:          g = generate_fcall;         break;
+        case SYMBOL_FLOAT:          g = generate_float;         break;
+        case SYMBOL_MEMBER:         g = generate_member;        break;
+        case SYMBOL_RETURN:         g = generate_return;        break;
+        case SYMBOL_SOURCE:         g = generate_source;        break;
+        case SYMBOL_STRING:         g = generate_string;        break;
+        case SYMBOL_INTEGER:        g = generate_integer;       break;
+        case SYMBOL_BOOLEAN:        g = generate_boolean;       break;
+        case SYMBOL_ITERLOOP:       g = generate_iterloop;      break;
+        case SYMBOL_VARIABLE:       g = generate_variable;      break;
+        case SYMBOL_STATEMENTS:     g = generate_statements;    break;
+        case SYMBOL_ASSIGNMENT:     g = generate_assignment;    break;
+        case SYMBOL_EXPRESSION:     g = generate_math;          break;
+        case SYMBOL_DESTINATION:    g = generate_destination;   break;
+        case SYMBOL_IF_THEN_ELSE:   g = generate_ifthenelse;    break;
+        case SYMBOL_COMPREHENSION:  g = generate_comprehension; break;
+        case SYMBOL_TRYCATCH:       g = generate_trycatch;      break;
+        case SYMBOL_THROW:          g = generate_throw;         break;
+        default:
+            return (struct byte_array*)exit_message(ERROR_TOKEN);
+    }
+
+    if (!code)
+        code = byte_array_new();
+    if (g)
+        g(code, root);
+    return code;
+}
+
+struct byte_array *generate_program(struct symbol *root)
+{
+    DEBUGPRINT("generate:\n");
+    struct byte_array *code = byte_array_new();
+    generate_code(code, root);
+    struct byte_array *program = serial_encode_int(0, 0, code->length);
+    byte_array_append(program, code);
+#ifdef DEBUG
+    display_program(program);
+#endif
+    return program;
+}
+
+// build ///////////////////////////////////////////////////////////////////
+
+struct byte_array *build_string(const struct byte_array *input) {
+    assert_message(input, ERROR_NULL);
+    struct byte_array *input_copy = byte_array_copy(input);
+    DEBUGPRINT("lex %d:\n", input_copy->length);
+    struct array* list = lex(input_copy);
+    struct symbol *tree = parse(list, 0);
+
+    return generate_program(tree);
+}
+
+struct byte_array *build_file(const struct byte_array* filename)
+{
+    struct byte_array *input = read_file(filename);
+    return build_string(input);
+}
+
+void compile_file(const char* str)
+{
+    struct byte_array *filename = byte_array_from_string(str);
+    struct byte_array *program = build_file(filename);
+    struct byte_array *dotfg = byte_array_from_string(EXTENSION_SRC);
+    struct byte_array *dotfgbc = byte_array_from_string(EXTENSION_BC);
+    int offset = byte_array_find(filename, dotfg, 0);
+    assert_message(offset > 0, "invalid source file name");
+    byte_array_replace(filename, dotfgbc, offset, dotfg->length);
+    write_file(filename, program);
+}
diff -r 000000000000 -r 1a89e28dea91 compile.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/compile.h	Wed May 30 21:13:01 2012 +0000
@@ -0,0 +1,12 @@
+#ifndef COMPILE_H
+
+#include "vm.h"
+
+#define EXTENSION_SRC    ".fg"
+#define EXTENSION_BC     ".fgbc"
+
+struct byte_array *build_string(const struct byte_array *input);
+struct byte_array *build_file(const struct byte_array* filename);
+void compile_file(const char* str);
+
+#endif // COMPILE_H
diff -r 000000000000 -r 1a89e28dea91 interpret.c
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/interpret.c	Wed May 30 21:13:01 2012 +0000
@@ -0,0 +1,100 @@
+//
+//  interpret.c
+//  filagree
+//
+
+#include "vm.h"
+#include "compile.h"
+#include "interpret.h"
+
+#define FG_MAX_INPUT     256
+#define ERROR_USAGE    "usage: filagree [file]"
+
+
+void yield(struct Context *context) {
+#ifdef DEBUG
+	struct stack *stack = context->rhs;
+	struct variable *f = stack_pop(stack);
+	struct byte_array *result = f->str;
+	byte_array_append(result, byte_array_from_string(": "));
+	while (!stack_empty(stack)) {
+		struct variable *v = stack_pop(stack);
+		byte_array_append(result, variable_value(context, v));
+	}
+	DEBUGPRINT("%s\n", byte_array_to_string(result));
+#endif
+}
+
+struct variable *repl()
+{
+    char stdinput[FG_MAX_INPUT];
+    struct variable *v = NULL;
+    struct Context *context = vm_init();
+	
+    for (;;) {
+        fflush(stdin);
+        stdinput[0] = 0;
+        if (!fgets(stdinput, FG_MAX_INPUT, stdin)) {
+            if (feof(stdin))
+                return 0;
+            if (ferror(stdin))
+                //return errno;
+                return variable_new_err(context, "unknown error reading stdin");
+        }
+        if ((v = interpret_string(stdinput, &yield)))
+            return v;
+    }
+}
+
+struct variable *interpret_file(const struct byte_array *filename, bridge *callback)
+{
+    struct byte_array *program = build_file(filename);
+    return execute(program, false, callback);
+}
+
+struct variable *execute_file(const struct byte_array* filename, bridge *callback)
+{
+    struct byte_array *program = read_file(filename);
+    return execute(program, false, callback);
+}
+
+struct variable *run_file(const char* str, bridge *callback)
+{
+    struct byte_array *filename = byte_array_from_string(str);
+    struct byte_array *dotfgbc = byte_array_from_string(EXTENSION_BC);
+    int fgbc = byte_array_find(filename, dotfgbc, 0);
+    if (fgbc > 0)
+        return execute_file(filename, callback);
+    struct byte_array *dotfg = byte_array_from_string(EXTENSION_SRC);
+    int fg = byte_array_find(filename, dotfg, 0);
+    if (fg > 0)
+        return interpret_file(filename, callback);
+    return (struct variable*)exit_message("invalid file name");
+}
+
+struct variable *interpret_string(const char *str, bridge *callback)
+{
+    struct variable *e;
+    struct byte_array *input = byte_array_from_string(str);
+    struct byte_array *program = build_string(input);
+    if (program && (e = execute(program, true, callback)) && (e->type == VAR_ERR))
+        printf("%s\n", byte_array_to_string(e->str));
+    return NULL;
+}
+
+#ifdef CLI
+int main (int argc, char** argv)
+{
+    struct variable *v = NULL;
+    switch (argc) {
+        case 1:     v = repl();				        break;
+        case 2:     v = run_file(argv[1], &yield);  break;
+        case 3:     compile_file(argv[1]);	        break;
+        default:    exit_message(ERROR_USAGE);	    break;
+    }
+    if (v && v->type==VAR_ERR)
+        log_print("%s\n", variable_value_str(NULL, v));
+    return v && v->type == VAR_ERR;
+}
+#endif // EXECUTABLE
+
diff -r 000000000000 -r 1a89e28dea91 interpret.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/interpret.h	Wed May 30 21:13:01 2012 +0000
@@ -0,0 +1,12 @@
+//
+//  interpret.h
+//  filagree
+//
+
+#ifndef INTERPRET_H
+#define INTERPRET_H
+
+struct variable *interpret_file(const struct byte_array *filename, bridge *callback);
+struct variable *interpret_string(const char *str, bridge *callback);
+
+#endif // INTERPRET_H
diff -r 000000000000 -r 1a89e28dea91 serial.c
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/serial.c	Wed May 30 21:13:01 2012 +0000
@@ -0,0 +1,213 @@
+/*
+ *    serial.c
+ *
+ *    stream serialization - serialies and deserializes byte_array and calls-back on each element
+ */
+
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <math.h>
+
+#include "serial.h"
+#include "struct.h"
+#include "vm.h"
+#include "util.h"
+
+// functions ///////////////////////////////////////////////////////////////
+
+// tells how many bytes are needed to encode this value
+uint8_t encode_int_size(int32_t value)
+{
+    uint8_t i;
+    value = (value >= 0 ? value : -value) >> 6;
+    for (i=1; value; i++, value >>=7);
+    return i;
+}
+
+struct byte_array *encode_int(struct byte_array *buf, int32_t value)
+{
+    if (!buf)
+		buf = byte_array_new();
+    uint8_t growth = encode_int_size(value);
+    byte_array_resize(buf, buf->length + growth);
+    bool neg = value < 0;
+    value = abs(value);
+    uint8_t byte = (value & 0x3F) | ((value >= 0x40) ? 0x80 : 0) | (neg ? 0x40 : 0);
+    *buf->current++ = byte;
+    value >>= 6;
+    while (value) {
+        byte = (value & 0x7F) | ((value >= 0x80) ? 0x80 : 0); 
+        *buf->current++ = byte; 
+        value >>= 7;
+    }
+    return buf;
+}
+
+struct byte_array* serial_encode_int(struct byte_array* buf, int32_t key, int32_t value) {
+    if (!buf)
+        buf = byte_array_new();
+    if (key)
+        encode_int(buf, key<<2 | SERIAL_INT);
+    encode_int(buf, value);
+    return buf;
+}
+
+int32_t serial_decode_int(struct byte_array* buf)
+{
+    bool neg = *buf->current & 0x40;
+    int32_t ret = *buf->current & 0x3F;
+    int bitpos = 6;
+    while ((*buf->current++ & 0x80) && (bitpos < (sizeof(int32_t)*8))) {
+        ret |= (*buf->current & 0x7F) << bitpos;
+        bitpos += 7;
+    }
+    return neg ? -ret : ret;
+}
+
+float serial_decode_float(struct byte_array* buf)
+{
+    float f;
+    uint8_t *uf = (uint8_t*)&f;
+    for (int i=4; i; i--) {
+        *uf = *buf->current;
+        uf++;
+        buf->current++;
+    }
+    //DEBUGPRINT("serial_decode_float %f\n", f);
+    return f;
+}
+
+struct byte_array* serial_decode_string(struct byte_array* buf)
+{
+	null_check(buf);
+    int32_t len = serial_decode_int(buf);
+	assert_message(len>=0, "negative malloc");
+    struct byte_array* ba = byte_array_new_size(len);
+    ba->data = ba->current = (uint8_t*)malloc(len);
+	null_check(ba->data);
+    memcpy(ba->data, buf->current, len);
+    buf->current += len;
+    return ba;
+}
+
+void serial_decode(struct byte_array* buf, serial_element se, const void* extra)
+{
+//    DEBUGPRINT("serial_decode %d %x<%x?\n", buf->size, buf->current, buf->data + buf->size);
+    while (buf->current < buf->data + buf->length)
+    {
+        // get key and wire type
+        int32_t keyWire = serial_decode_int(buf);
+        struct key_value_pair pair = {
+            .key = keyWire >> 2,
+            .wire_type = (enum serial_type)(keyWire & 0x03)
+        };
+//        DEBUGPRINT("serial_decode %d:%d\n", pair.key, pair.wire_type);
+
+        // get data
+        switch(pair.wire_type) {
+            case SERIAL_INT:  /* int */
+                pair.value.integer = serial_decode_int(buf);
+                break;
+            case SERIAL_FLOAT:
+                pair.value.floater = serial_decode_float(buf);
+            case SERIAL_STRING:  /* bytes */
+                pair.value.bytes = serial_decode_string(buf);
+                break;
+            case SERIAL_ARRAY:
+                break;
+            default:
+                DEBUGPRINT("serial_decode ?\n");
+                break;
+        }
+        if (se(&pair, buf, extra)) {
+//            DEBUGPRINT("serial_decode: break\n");
+            break;
+        }
+    }
+//    DEBUGPRINT("serial_decode done\n");
+}
+
+// assume little endian
+struct byte_array *encode_float(struct byte_array *buf, float f)
+{
+    assert_message(sizeof(float)==4, "bad float size");
+    uint8_t *uf = (uint8_t*)&f;
+    for (int i=4; i; i--) {
+        byte_array_add_byte(buf, *uf);
+        uf++;
+    }
+    return buf;
+}
+
+struct byte_array* serial_encode_float(struct byte_array* buf, int32_t key, float value) {
+    if (!buf)
+        buf = byte_array_new();
+    if (key)
+        encode_int(buf, key<<2 | SERIAL_FLOAT);
+    encode_float(buf, value);
+    return buf;
+}
+
+uint8_t serial_encode_string_size(int32_t key, const struct byte_array* string) {
+    if (!string)
+        return 0;
+    return (key ? encode_int_size(key) : 0) +
+           encode_int_size(string->length) +
+           string->length;
+}
+
+struct byte_array* serial_encode_string(struct byte_array* buf, int32_t key, const struct byte_array* bytes)
+{
+    if (!bytes)
+        return buf;
+    if (!buf)
+        buf = byte_array_new();
+
+    if (key)
+        encode_int(buf, key<<2 | SERIAL_STRING);
+    encode_int(buf, bytes->length);
+    byte_array_resize(buf, buf->length + bytes->length);
+    memcpy(buf->current, bytes->data, bytes->length);
+
+    buf->current = buf->data + buf->length;
+    return buf;
+}
+
+struct byte_array* serial_encode_array(struct byte_array* buf, int32_t key, int32_t count) {
+    if (!buf) buf = byte_array_new();
+    encode_int(buf, key<<2 | SERIAL_ARRAY);
+    encode_int(buf, count);
+    return buf;
+}
+
+#ifdef DEBUG
+
+bool display_serial(const struct key_value_pair* kvp) {
+    DEBUGPRINT("serialElementDebug %d:\t", kvp->key);
+    char* str;
+
+    switch (kvp->wire_type) {
+        case SERIAL_ERROR:
+            DEBUGPRINT("error %d\n", kvp->value.serialError);
+            break;
+        case SERIAL_INT:
+            DEBUGPRINT("int %d\n", kvp->value.integer);
+            break;
+        case SERIAL_FLOAT:
+            DEBUGPRINT("float %f\n", kvp->value.floater)
+        case SERIAL_STRING:
+            str = (char*)malloc(kvp->value.bytes->length + 1);
+            memcpy(str, kvp->value.bytes->data, kvp->value.bytes->length);
+            str[kvp->value.bytes->length] = 0;
+            DEBUGPRINT("bytes %s\n", str);
+            break;
+        case SERIAL_ARRAY:
+            DEBUGPRINT("array\n");
+            break;            
+    }
+    return true;
+}
+
+#endif // DEBUG
diff -r 000000000000 -r 1a89e28dea91 serial.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/serial.h	Wed May 30 21:13:01 2012 +0000
@@ -0,0 +1,68 @@
+/* serial.h
+ *
+ *	[de]serialization API
+ */
+
+#ifndef SERIAL_H
+#define SERIAL_H
+
+
+#include <stdint.h> 
+#include "struct.h"
+
+
+enum serial_type {
+	SERIAL_ERROR,
+	SERIAL_INT,
+	SERIAL_FLOAT,	
+	SERIAL_STRING,
+	SERIAL_ARRAY,
+};
+
+
+struct key_value_pair
+{
+	int32_t key;
+	
+	enum serial_type wire_type;
+	
+	union {
+		
+		int32_t integer;
+		float floater;
+		struct byte_array* bytes;
+		enum {
+			SOMETHING_HAS_GONE_HORRIBLY_WRONG,
+		} serialError;
+		
+	} value;
+};
+
+
+typedef bool (serial_element)(const struct key_value_pair*,
+							  struct byte_array* bytes,
+							  const void* extra);
+bool serial_element_debug(const struct key_value_pair* kvp);
+
+struct byte_array* serial_encode_int(struct byte_array* buf,
+									  int32_t key,
+									  int32_t value);
+
+struct byte_array *serial_encode_float(struct byte_array *buf,
+									   int32_t key,
+									   float value);
+
+struct byte_array* serial_encode_string(struct byte_array* buf,
+										int32_t key,
+										const struct byte_array* string);
+void serial_decode(struct byte_array* buf,
+				   serial_element* se,
+				   const void* extra);
+
+int32_t serial_decode_int(struct byte_array* buf);
+
+float serial_decode_float(struct byte_array* buf);
+
+struct byte_array* serial_decode_string(struct byte_array* buf);
+
+#endif // SERIAL_H
diff -r 000000000000 -r 1a89e28dea91 struct.c
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/struct.c	Wed May 30 21:13:01 2012 +0000
@@ -0,0 +1,516 @@
+/* struct.c
+ *
+ * implements array, byte_array, lifo and map
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdarg.h>
+#include <assert.h>
+#include <ctype.h>
+
+#include "vm.h"
+#include "struct.h"
+#include "util.h"
+
+#define BYTE_ARRAY_MAX_LEN      10000
+#define ERROR_BYTE_ARRAY_LEN    "byte array too long"
+
+
+// array ///////////////////////////////////////////////////////////////////
+
+struct array *array_new() {
+    return array_new_size(0);
+}
+
+struct array *array_new_size(uint32_t size) {
+    struct array *a = (struct array*)malloc(sizeof(struct array));
+    a->data = a->current = NULL;
+    a->length = 0;
+    return a;
+}
+
+void array_del(struct array *a) {
+    for (int i=0; i<a->length; i++)
+        free(array_get(a, i));
+    free(a->data);
+    free(a);
+}
+
+void array_resize(struct array *a, uint32_t length) {
+    a->data = (void**)realloc(a->data, length * sizeof(void*));
+    null_check(a->data);
+    memset(&a->data[a->length], 0, length-a->length);
+    a->length = length;
+}
+
+uint32_t array_add(struct array *a, void *datum) {
+    a->data = (void**)realloc(a->data, (a->length+1) * sizeof(void*));
+    a->data[a->length++] = datum;
+    return a->length-1;
+}
+
+void array_insert(struct array *a, uint32_t index, void *datum)
+{
+    a->data = (void**)realloc(a->data, (a->length+1) * sizeof(void*));
+    uint32_t i;
+    for (i=a->length; i>index; i--)
+        a->data[i] = a->data[i-1];
+    a->data[i] = datum;
+    a->length++;
+}
+
+void* array_get(const struct array *a, uint32_t index) {
+    assert_message(a && index < a->length, ERROR_INDEX);
+    //DEBUGPRINT("array_get %d = %x\n", index, a->data[index]);
+    return a->data[index];
+}
+
+void array_set(struct array *a, uint32_t index, void* datum) {
+    null_check(a);
+    null_check(datum);
+    if (a->length <= index)
+        array_resize(a, index+1);
+    //DEBUGPRINT("array_set %d %x\n", index, datum);
+    a->data[index] = datum;
+}
+
+void *list_remove(void *data, uint32_t *end, uint32_t start, int32_t length, size_t width)
+{
+    null_check(data);
+    null_check(end);
+    length = length < 0 ? *end - start : length;
+    assert_message(start < *end && start+length <= *end, "index out of bounds");
+    
+    memmove((uint8_t*)data+start*width, (uint8_t*)data+(start+length)*width, (*end-start-length)*width);
+    *end -= (uint32_t)length;
+    return realloc(data, *end * width);
+}
+
+void array_remove(struct array *self, uint32_t start, int32_t length) {
+    self->data = (void**)list_remove(self->data, &self->length, start, length, sizeof(void*));
+}
+
+struct array *array_copy(const struct array* original) {
+    if (!original)
+        return NULL;
+    struct array* copy = (struct array*)malloc(sizeof(struct array));
+    copy->data = (void**)malloc(original->length);
+    memcpy(copy->data, original->data, original->length);
+    copy->length = original->length;
+    copy->current = copy->data + (original->current - original->data);
+    return copy;
+}
+
+struct array *array_part(struct array *within, uint32_t start, uint32_t length)
+{
+    struct array *p = array_copy(within);
+    array_remove(p, start+length, within->length-start-length);
+    array_remove(p, 0, start);
+    return p;
+}
+
+void array_append(struct array *a, const struct array* b)
+{
+    null_check(a);
+    null_check(b);
+    array_resize(a, a->length + b->length);
+    memcpy(&a->data[a->length], b->data, b->length);
+    a->current = a->data + a->length;
+}
+
+// byte_array ///////////////////////////////////////////////////////////////
+
+struct byte_array *byte_array_new() {
+    struct byte_array* ba = (struct byte_array*)malloc(sizeof(struct byte_array));
+    ba->data = ba->current = 0;
+    ba->length = 0;
+    return ba;
+}
+
+void byte_array_del(struct byte_array* ba) {
+    if (ba->data)
+        free(ba->data);
+    free(ba);
+}
+
+struct byte_array *byte_array_new_size(uint32_t size) {
+    struct byte_array* ba = (struct byte_array*)malloc(sizeof(struct byte_array));
+    ba->data = ba->current = (uint8_t*)malloc(size);
+    ba->length = size;
+    return ba;
+}
+
+void byte_array_resize(struct byte_array* ba, uint32_t size) {
+    assert_message(ba->current >= ba->data, "byte_array corrupt");
+    uint32_t delta = ba->current - ba->data;
+    ba->data = (uint8_t*)realloc(ba->data, size);
+    assert(ba->data);
+    ba->current = ba->data + delta;
+    ba->length = size;
+}
+
+bool byte_array_equals(const struct byte_array *a, const struct byte_array* b) {
+    if (a==b)
+        return true;
+    if (!a != !b) // one is null and the other is not
+        return false;
+    if (a->length != b->length)
+        return false;
+    
+    int i;
+    for (i = 0; i<a->length; i++)
+        if (a->data[i] != b->data[i])
+            return false;
+    return true;
+}
+
+struct byte_array *byte_array_copy(const struct byte_array* original) {
+    if (!original)
+        return NULL;
+    struct byte_array* copy = (struct byte_array*)malloc(sizeof(struct byte_array));
+    copy->data = (uint8_t*)malloc(original->length);
+    memcpy(copy->data, original->data, original->length);
+    copy->length = original->length;
+    copy->current = copy->data + (original->current - original->data);
+    return copy;
+}
+
+void byte_array_append(struct byte_array *a, const struct byte_array* b) {
+    null_check(a);
+    null_check(b);
+    uint32_t offset = a->length;
+    byte_array_resize(a, a->length + b->length);
+    memcpy(&a->data[offset], b->data, b->length);
+    a->current = a->data + a->length;
+}
+
+void byte_array_remove(struct byte_array *self, uint32_t start, int32_t length) {
+    self->data = (uint8_t*)list_remove(self->data, &self->length, start, length, sizeof(uint8_t));
+}
+
+struct byte_array *byte_array_part(struct byte_array *within, uint32_t start, uint32_t length)
+{
+    struct byte_array *p = byte_array_copy(within);
+    byte_array_remove(p, start+length, within->length-start-length);
+    byte_array_remove(p, 0, start);
+    return p;
+}
+
+struct byte_array *byte_array_from_string(const char* str)
+{
+    int len = strlen(str);
+    struct byte_array* ba = byte_array_new_size(len);
+    memcpy(ba->data, str, len);
+    return ba;
+}
+
+char* byte_array_to_string(const struct byte_array* ba)
+{
+    int len = ba->length;
+    char* s = (char*)malloc(len+1);
+    memcpy(s, ba->data, len);
+    s[len] = 0;
+    return s;
+}
+
+void byte_array_reset(struct byte_array* ba) {
+    ba->current = ba->data;
+}
+
+struct byte_array *byte_array_concatenate(int n, const struct byte_array* ba, ...)
+{
+    struct byte_array* result = byte_array_copy(ba);
+
+    va_list argp;
+    for(va_start(argp, ba); --n;) {
+        struct byte_array* parameter = va_arg(argp, struct byte_array* );
+        if (!parameter)
+            continue;
+        assert_message(result->length + parameter->length < BYTE_ARRAY_MAX_LEN, ERROR_BYTE_ARRAY_LEN);
+        byte_array_append(result, parameter);
+    }
+
+    va_end(argp);
+
+    if (result)
+        result->current = result->data + result->length;
+    return result;
+}
+
+struct byte_array *byte_array_add_byte(struct byte_array *a, uint8_t b) {
+    byte_array_resize(a, a->length+1);
+    a->current = a->data + a->length;
+    a->data[a->length-1] = b;
+    return a;
+}
+
+void byte_array_print(const char* text, const struct byte_array* ba) {
+    int offset = ba->current-ba->data;
+    if (text)
+        printf("%s @%d\n", text, offset);
+    for (int i=0; i<ba->length; i++)
+        printf("\t%s%d\n", i==offset?">":" ", ba->data[i]);
+}
+
+int32_t byte_array_find(struct byte_array *within, struct byte_array *sought, uint32_t start)
+{
+    null_check(within);
+    null_check(sought);
+    
+    uint32_t ws = within->length;
+    uint32_t ss = sought->length;
+    assert_message(start < within->length, "out of bounds");
+    
+    uint8_t *wd = within->data;
+    uint8_t *sd = sought->data;
+    for (int32_t i=start; i<ws-ss+1; i++)
+        if (!memcmp(wd + i, sd, ss)) 
+            return i; 
+    
+    return -1;
+}
+
+struct byte_array *byte_array_replace(struct byte_array *within, struct byte_array *replacement, uint32_t start, int32_t length)
+{
+    null_check(within);
+    null_check(replacement);
+    uint32_t ws = within->length;
+    assert_message(start < ws, "index out of bounds");
+    if (length < 0)
+        length = ws - start;
+    
+    int32_t new_length = within->length - length + replacement->length;
+    struct byte_array *replaced = byte_array_new_size(new_length);
+    
+    memcpy(replaced->data, within->data, start);
+    memcpy(replaced->data + start, replacement->data, replacement->length);
+    memcpy(replaced->data + start + replacement->length, within->data + start + length, within->length - start - length);
+    
+    return replaced;
+}
+
+
+// stack ////////////////////////////////////////////////////////////////////
+
+struct stack* stack_new() {
+    return (struct stack*)calloc(sizeof(struct stack), 1);
+}
+
+struct stack_node* stack_node_new() {
+    return (struct stack_node*)calloc(sizeof(struct stack_node), 1);
+}
+
+void stack_push(struct stack* stack, void* data)
+{
+    null_check(data);
+    if (!stack->head)
+        stack->head = stack->tail = stack_node_new();
+    else {
+        struct stack_node* old_head = stack->head;
+        stack->head = stack_node_new();
+        null_check(stack->head);
+        stack->head->next = old_head;
+    }
+    stack->head->data = data;
+}
+
+void* stack_pop(struct stack* stack)
+{
+    if (!stack->head)
+        return NULL;
+    void* data = stack->head->data;
+    stack->head = stack->head->next;
+    null_check(data);
+    return data;
+}
+
+void* stack_peek(const struct stack* stack, uint8_t index)
+{
+    null_check(stack);
+    struct stack_node*p = stack->head;
+    for (; index && p; index--, p=p->next);
+    return p ? p->data : NULL;
+}
+
+bool stack_empty(const struct stack* stack)
+{
+    null_check(stack);
+    return stack->head == NULL;// && stack->tail == NULL;
+}
+
+// map /////////////////////////////////////////////////////////////////////
+
+static size_t def_hash_func(const struct byte_array* key)
+{
+    size_t hash = 0;
+    int i = 0;
+    for (i = 0; i<key->length; i++)
+        hash += key->data[i];
+    return hash;
+}
+
+struct map* map_new()
+{
+    struct map* m;
+    if (!(m =(struct map*)malloc(sizeof(struct map)))) return NULL;
+    m->size = 16;
+    m->hash_func = def_hash_func;
+    
+    if (!(m->nodes = (struct hash_node**)calloc(m->size, sizeof(struct hash_node*)))) {
+        free(m);
+        return NULL;
+    }
+    
+    return m;
+}
+
+void map_del(struct map* m)
+{
+    DEBUGPRINT("map_destroy\n");
+    size_t n;
+    struct hash_node *node, *oldnode;
+    
+    for(n = 0; n<m->size; ++n) {
+        node = m->nodes[n];
+        while (node) {
+            byte_array_del(node->key);
+            oldnode = node;
+            node = node->next;
+            free(oldnode);
+        }
+    }
+    free(m->nodes);
+    free(m);
+}
+
+int map_insert(struct map* m, const struct byte_array* key, void *data)
+{
+    struct hash_node *node;
+    size_t hash = m->hash_func(key) % m->size;    
+    
+    node = m->nodes[hash];
+    while (node) {
+        if (byte_array_equals(node->key, key)) {
+            node->data = data;
+            return 0;
+        }
+        node = node->next;
+    }
+    
+    if (!(node = (struct hash_node*)malloc(sizeof(struct hash_node))))
+        return -1;
+    if (!(node->key = byte_array_copy(key))) {
+        free(node);
+        return -1;
+    }
+    node->data = data;
+    node->next = m->nodes[hash];
+    m->nodes[hash] = node;
+    
+    return 0;
+}
+
+struct array* map_keys(const struct map* m) {
+    struct array *a = array_new();
+    for (int i=0; i<m->size; i++)
+        for (const struct hash_node* n = m->nodes[i]; n; n=n->next)
+            if (n->data)
+                array_add(a, n->key);
+    return a;
+}
+
+struct array* map_values(const struct map* m) {
+    struct array *a = array_new();
+    for (int i=0; i<m->size; i++)
+        for (const struct hash_node* n = m->nodes[i]; n; n=n->next)
+            if (n->data)
+                array_add(a, n->data);
+    return a;
+}
+
+int map_remove(struct map* m, const struct byte_array* key)
+{
+    struct hash_node *node, *prevnode = NULL;
+    size_t hash = m->hash_func(key)%m->size;
+    
+    node = m->nodes[hash];
+    while(node) {
+        if (byte_array_equals(node->key, key)) {
+            byte_array_del(node->key);
+            if (prevnode) prevnode->next = node->next;
+            else m->nodes[hash] = node->next;
+            free(node);
+            return 0;
+        }
+        prevnode = node;
+        node = node->next;
+    }    
+    return -1;
+}
+
+bool map_has(const struct map* m, const struct byte_array* key) {
+    struct hash_node *node;
+    size_t hash = m->hash_func(key) % m->size;
+    node = m->nodes[hash];
+    while (node) {
+        if (byte_array_equals(node->key, key))
+            return true;
+        node = node->next;
+    }
+    return false;
+}
+
+void *map_get(const struct map* m, const struct byte_array* key)
+{
+    struct hash_node *node;
+    size_t hash = m->hash_func(key) % m->size;
+    node = m->nodes[hash];
+    while (node) {
+        if (byte_array_equals(node->key, key))
+            return node->data;
+        node = node->next;
+    }
+    return NULL;
+}
+
+int map_resize(struct map* m, size_t size)
+{
+    DEBUGPRINT("map_resize\n");
+    struct map newtbl;
+    size_t n;
+    struct hash_node *node,*next;
+    
+    newtbl.size = size;
+    newtbl.hash_func = m->hash_func;
+    
+    if (!(newtbl.nodes = (struct hash_node**)calloc(size, sizeof(struct hash_node*))))
+        return -1;
+    
+    for(n = 0; n<m->size; ++n) {
+        for(node = m->nodes[n]; node; node = next) {
+            next = node->next;
+            map_insert(&newtbl, node->key, node->data);
+            map_remove(m, node->key);
+            
+        }
+    }
+    
+    free(m->nodes);
+    m->size = newtbl.size;
+    m->nodes = newtbl.nodes;
+    
+    return 0;
+}
+
+// in case of intersection, a wins
+void map_update(struct map *a, const struct map *b)
+{
+    const struct array *keys = map_keys(b);
+    for (int i=0; i<keys->length; i++) {
+        const struct byte_array *key = (const struct byte_array*)array_get(keys, i);
+        if (!map_has(a, key))
+            map_insert(a, key, map_get(b, key));
+    }
+}
diff -r 000000000000 -r 1a89e28dea91 struct.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/struct.h	Wed May 30 21:13:01 2012 +0000
@@ -0,0 +1,108 @@
+/* struct.h
+ *
+ * APIs for array, byte_array, [f|l]ifo and map
+ */
+
+#ifndef STRUCT_H
+#define STRUCT_H
+
+
+#include <inttypes.h>
+#include <stdbool.h>
+#include <stdlib.h>
+
+
+#define ERROR_INDEX	"index out of bounds"
+#define ERROR_NULL "null pointer"
+
+
+// array ///////////////////////////////////////////////////////////////////
+
+struct array {
+	void **data, **current;
+	uint32_t length;
+};
+
+struct array *array_new();
+void array_del(struct array *a);
+struct array *array_new_size(uint32_t size);
+void array_resize(struct array *a, uint32_t length);
+uint32_t array_add(struct array *a , void *datum);
+void array_insert(struct array *a, uint32_t index, void *datam);
+void* array_get(const struct array *a, uint32_t index);
+void array_set(struct array *a, uint32_t index, void *datum);
+void array_remove(struct array *a, uint32_t start, int32_t length);
+struct array *array_part(struct array *within, uint32_t start, uint32_t length);
+void array_append(struct array *a, const struct array* b);
+
+// byte_array ///////////////////////////////////////////////////////////////
+
+struct byte_array {
+	uint8_t *data, *current;
+	uint32_t length;
+};
+
+struct byte_array *byte_array_new();
+struct byte_array *byte_array_new_size(uint32_t size);
+void byte_array_append(struct byte_array *a, const struct byte_array* b);
+struct byte_array *byte_array_from_string(const char* str);
+char* byte_array_to_string(const struct byte_array* ba);
+void byte_array_del(struct byte_array* ba);
+struct byte_array *byte_array_copy(const struct byte_array* original);
+struct byte_array *byte_array_add_byte(struct byte_array *a, uint8_t b);
+void byte_array_reset(struct byte_array* ba);
+void byte_array_resize(struct byte_array* ba, uint32_t size);
+bool byte_array_equals(const struct byte_array *a, const struct byte_array* b);
+struct byte_array *byte_array_concatenate(int n, const struct byte_array* ba, ...);
+void byte_array_print(const char* text, const struct byte_array* ba);
+int32_t byte_array_find(struct byte_array *within, struct byte_array *sought, uint32_t start);
+struct byte_array *byte_array_part(struct byte_array *within, uint32_t start, uint32_t length);
+void byte_array_remove(struct byte_array *within, uint32_t start, int32_t length);
+struct byte_array *byte_array_replace(struct byte_array *within, struct byte_array *replacement, uint32_t start, int32_t length);
+
+// stack ////////////////////////////////////////////////////////////////////
+
+struct stack_node {
+	void* data;
+	struct stack_node* next;
+};
+
+struct stack {
+	struct stack_node* head;
+	struct stack_node* tail;
+};
+
+struct stack* stack_new();
+struct stack_node* stack_node_new();
+void fifo_push(struct stack* fifo, void* data);
+void stack_push(struct stack* stack, void* data);
+void* stack_pop(struct stack* stack);
+void* stack_peek(const struct stack* stack, uint8_t index);
+bool stack_empty(const struct stack* stack);
+
+// map /////////////////////////////////////////////////////////////////////
+
+struct hash_node {
+	struct byte_array *key;
+	void *data;
+	struct hash_node *next;
+};
+
+struct map {
+	size_t size;
+	struct hash_node **nodes;
+	size_t (*hash_func)(const struct byte_array*);
+};
+
+struct map* map_new();
+void map_del(struct map* map);
+int map_insert(struct map* map, const struct byte_array *key, void *data);
+int map_remove(struct map* map, const struct byte_array *key);
+void *map_get(const struct map* map, const struct byte_array *key);
+bool map_has(const struct map* map, const struct byte_array *key);
+int map_resize(struct map* map, size_t size);
+struct array* map_keys(const struct map* m);
+struct array* map_values(const struct map* m);
+void map_update(struct map *a, const struct map *b);
+
+#endif // STRUCT_H
diff -r 000000000000 -r 1a89e28dea91 sys.c
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/sys.c	Wed May 30 21:13:01 2012 +0000
@@ -0,0 +1,430 @@
+#include "serial.h"
+#include "sys.h"
+#include "struct.h"
+#include "variable.h"
+#include "vm.h"
+#include "util.h"
+#include <stdio.h>
+#include <string.h>
+
+// system functions
+
+void sys_callback2c(struct Context *context)
+{
+    stack_pop(context->rhs); // self
+	context->callback2c(context);
+}
+
+void sys_print(struct Context *context)
+{
+    stack_pop(context->rhs); // self
+    struct variable *v;
+    while ((v = (struct variable*)stack_pop(context->rhs)))
+        printf("%s\n", variable_value_str(context, v));
+}
+
+void sys_save(struct Context *context)
+{
+    stack_pop(context->rhs); // self
+    struct variable *v = (struct variable*)stack_pop(context->rhs);
+    struct variable *path = (struct variable*)stack_pop(context->rhs);
+    variable_save(context, v, path);
+}
+
+void sys_load(struct Context *context)
+{
+    stack_pop(context->rhs); // self
+    struct variable *path = (struct variable*)stack_pop(context->rhs);
+    struct variable *v = variable_load(context, path);
+
+    if (v)
+        stack_push(context->operand_stack, v);
+}
+
+void sys_rm(struct Context *context)
+{
+    stack_pop(context->rhs); // self
+    struct variable *path = (struct variable*)(struct variable*)stack_pop(context->rhs);
+    remove(byte_array_to_string(path->str));
+}
+
+struct string_func builtin_funcs[] = {
+	{"yield", (bridge*)&sys_callback2c},
+    {"print", (bridge*)&sys_print},
+    {"save", (bridge*)&sys_save},
+    {"load", (bridge*)(bridge*)&sys_load},
+    {"remove", (bridge*)&sys_rm},
+};
+
+struct variable *func_map(struct Context *context)
+{
+    struct map *map = map_new();
+    for (int i=0; i<ARRAY_LEN(builtin_funcs); i++) {
+        struct byte_array *name = byte_array_from_string(builtin_funcs[i].name);
+        struct variable *value = variable_new_c(context, builtin_funcs[i].func);
+        map_insert(map, name, value);
+    }
+    return variable_new_map(context, map);
+}
+
+// built-in member functions
+
+#define FNC_STRING      "string"
+#define FNC_LIST        "list"
+#define FNC_TYPE        "type"
+#define FNC_LENGTH      "length"
+#define FNC_KEYS        "keys"
+#define FNC_VALUES      "values"
+#define FNC_SERIALIZE   "serialize"
+#define FNC_DESERIALIZE "deserialize"
+#define FNC_SORT        "sort"
+#define FNC_FIND        "find"
+#define FNC_REPLACE     "replace"
+#define FNC_PART        "part"
+#define FNC_REMOVE        "remove"
+#define FNC_INSERT        "insert"
+
+struct variable *comparator = NULL;
+
+int (compar)(struct Context *context, const void *a, const void *b)
+{
+    struct variable *av = *(struct variable**)a;
+    struct variable *bv = *(struct variable**)b;
+
+    if (comparator) {
+
+        assert_message(comparator->type == VAR_FNC, "non-function comparator");
+        stack_push(context->rhs, av);
+        stack_push(context->rhs, bv);
+        byte_array_reset(comparator->str);
+        stack_push(context->operand_stack, comparator);
+        vm_call(context);
+
+        struct variable *result = (struct variable*)stack_pop(context->rhs);
+        assert_message(result->type == VAR_INT, "non-integer comparison result");
+        return result->integer;
+
+    } else {
+
+        enum VarType at = av->type;
+        enum VarType bt = bv->type;
+
+        if (at == VAR_INT && bt == VAR_INT) {
+            // DEBUGPRINT("compare %p:%d to %p:%d : %d\n", av, av->integer, bv, bv->integer, av->integer - bv->integer);
+            return av->integer - bv->integer;
+        } else
+            DEBUGPRINT("can't compare %s to %s\n", var_type_str(at), var_type_str(bt));
+
+        vm_exit_message(context, "incompatible types for comparison");
+        return 0;
+    }
+}
+
+int testarr[] = { 6, 5, 3, 1, 8, 7, 2, 4 };
+//int testarr[] = { 2,1 };
+int len = sizeof(testarr)/sizeof(testarr[0]);
+
+void heapset(size_t width, void *base0, uint32_t index0, void *base1, uint32_t index1) {
+    uint8_t *p0 = (uint8_t*)base0 + index0 * width;
+    uint8_t *p1 = (uint8_t*)base1 + index1 * width;
+    while (width--)
+        *(p0 + width) = *(p1 + width);
+}
+
+int heapcmp(struct Context *context,
+            int (*compar)(struct Context *, const void *, const void *),
+            size_t width, void *base0, uint32_t index0, void *base1, uint32_t index1) {
+    uint8_t *p0 = (uint8_t*)base0 + index0 * width;
+    uint8_t *p1 = (uint8_t*)base1 + index1 * width;
+    return compar(context, p0, p1);
+}
+
+int heapsortfg(struct Context *context,
+               void *base, size_t nel, size_t width,
+               int (*compar)(struct Context *, const void *, const void *))
+{
+    void *t = malloc(width); // the temporary value
+    unsigned int n = nel, parent = nel/2, index, child; // heap indexes
+    for (;;) { // loop until array is sorted
+        if (parent > 0) { // first stage - Sorting the heap
+            heapset(width, t, 0, base, --parent);
+        } else { // second stage - Extracting elements in-place
+            if (!--n) { // make the heap smaller
+                free(t);
+                return 0; // When the heap is empty, we are done
+            }
+            heapset(width, t, 0, base, n);
+            heapset(width, base, n, base, 0);
+        }
+        // insert operation - pushing t down the heap to replace the parent
+        index = parent; // start at the parent index
+        child = index * 2 + 1; // get its left child index
+        while (child < n) {
+            if (child + 1 < n  && // choose the largest child
+                heapcmp(context, compar, width, base, child+1, base, child) > 0) {
+                child++; // right child exists and is bigger
+            }
+            // is the largest child larger than the entry?
+            if (heapcmp(context, compar, width, base, child, t, 0) > 0) {
+                heapset(width, base, index, base, child);
+                index = child; // move index to the child
+                child = index * 2 + 1; // get the left child and go around again
+            } else
+                break; // t's place is found
+        }
+        // store the temporary value at its new location
+        heapset(width, base, index, t, 0);
+    }
+}
+
+void cfnc_sort(struct Context *context)
+{
+    struct variable *self = (struct variable*)stack_pop(context->rhs);
+    assert_message(self->type == VAR_LST, "sorting a non-list");
+    comparator = (struct variable*)stack_pop(context->rhs);
+
+    int num_items = self->list->length;
+
+    int success = heapsortfg(context, self->list->data, num_items, sizeof(struct variable*), &compar);
+    assert_message(!success, "error sorting");
+}
+
+struct variable *variable_part(struct Context *context, struct variable *self, uint32_t start, int32_t length)
+{
+    null_check(self);
+    switch (self->type) {
+        case VAR_STR: {
+            struct byte_array *str = byte_array_part(self->str, start, length);
+            return variable_new_str(context, str);
+        }
+        case VAR_LST: {
+            struct array *list = array_part(self->list, start, length);
+            return variable_new_list(context, list);
+        }
+        default:
+            return (struct variable*)exit_message("bad part type");
+    }
+}
+
+void variable_remove(struct variable *self, uint32_t start, int32_t length)
+{
+    null_check(self);
+    switch (self->type) {
+        case VAR_STR:
+            byte_array_remove(self->str, start, length);
+            break;
+        case VAR_LST:
+            array_remove(self->list, start, length);
+            break;
+        default:
+            exit_message("bad remove type");
+    }
+}
+
+struct variable *variable_concatenate(struct Context *context, int n, const struct variable* v, ...)
+{
+    struct variable* result = variable_copy(context, v);
+
+    va_list argp;
+    for(va_start(argp, v); --n;) {
+        struct variable* parameter = va_arg(argp, struct variable* );
+        if (!parameter)
+            continue;
+        else if (!result)
+            result = variable_copy(context, parameter);
+        else switch (result->type) {
+            case VAR_STR: byte_array_append(result->str, parameter->str); break;
+            case VAR_LST: array_append(result->list, parameter->list);    break;
+            default: return (struct variable*)exit_message("bad concat type");
+        }
+    }
+
+    va_end(argp);
+    return result;
+}
+
+void cfnc_chop(struct Context *context, bool part)
+{
+    struct variable *self = (struct variable*)stack_pop(context->rhs);
+    struct variable *start = (struct variable*)stack_pop(context->rhs);
+    struct variable *length = (struct variable*)stack_pop(context->rhs);
+    assert_message(start->type == VAR_INT, "non-integer index");
+    assert_message(length->type == VAR_INT, "non-integer length");
+    int32_t beginning = start->integer;
+    int32_t foraslongas = length->integer;
+
+    struct variable *result = variable_copy(context, self);
+    if (part)
+        result = variable_part(context, result, beginning, foraslongas);
+    else
+        variable_remove(result, beginning, foraslongas);
+    stack_push(context->operand_stack, result);
+}
+
+static inline void cfnc_part(struct Context *context) {
+    cfnc_chop(context, true);
+}
+
+static inline void cfnc_remove(struct Context *context) {
+    cfnc_chop(context, false);
+}
+
+void cfnc_find(struct Context *context)
+{
+    struct variable *self = (struct variable*)stack_pop(context->rhs);
+    struct variable *sought = (struct variable*)stack_pop(context->rhs);
+    struct variable *start = (struct variable*)stack_pop(context->rhs);
+
+    null_check(self);
+    null_check(sought);
+    assert_message(self->type == VAR_STR, "searching in a non-list");
+    assert_message(sought->type == VAR_STR, "searching for a non-list");
+    if (start) assert_message(start->type == VAR_INT, "non-integer index");
+
+    int32_t beginning = start ? start->integer : 0;
+    int32_t index = byte_array_find(self->str, sought->str, beginning);
+    struct variable *result = variable_new_int(context, index);
+    stack_push(context->operand_stack, result);
+}
+
+void cfnc_insert(struct Context *context)
+{
+    struct variable *self = (struct variable*)stack_pop(context->rhs);
+    struct variable *start = (struct variable*)stack_pop(context->rhs);
+    struct variable *insertion = (struct variable*)stack_pop(context->rhs);
+    assert_message(start->type == VAR_INT, "non-integer index");
+    assert_message(insertion && insertion->type == self->type, "insertion doesn't match destination");
+
+    int32_t position = start->integer;
+    struct variable *first = variable_part(context, variable_copy(context, self), 0, position);
+    struct variable *second = variable_part(context, variable_copy(context, self), position, -1);
+    struct variable *joined = variable_concatenate(context, 3, first, self, second);
+    stack_push(context->operand_stack, joined);
+}
+
+//    a                b        c
+// <sought> <replacement> [<start>]
+// <start> <length> <replacement>
+void replace(struct Context *context)
+{
+    struct variable *self = (struct variable*)stack_pop(context->rhs);
+    struct variable *a = (struct variable*)stack_pop(context->rhs);
+    struct variable *b = (struct variable*)stack_pop(context->rhs);
+    struct variable *c = (struct variable*)stack_pop(context->rhs);
+    
+    null_check(self);
+    null_check(b);
+    assert_message(self->type == VAR_STR, "searching in a non-string");
+    
+    int32_t where = 0;
+    struct byte_array *replaced = self->str;
+    
+    if (a->type == VAR_STR) { // find a, replace with b
+        
+        assert_message(b->type == VAR_STR, "non-string replacement");
+        
+        if (c) { // replace first match after index b
+            
+            assert_message(c->type == VAR_INT, "non-integer index");
+            uint32_t found = byte_array_find(self->str, a->str, c->integer);
+            replaced = byte_array_replace(self->str, b->str, found, b->str->length);
+            
+        } else for(;;) { // replace all
+            
+            if ((where = byte_array_find(self->str, a->str, where)) < 0)
+                break;
+            replaced = byte_array_replace(replaced, b->str, where++, a->str->length);            
+        }
+        
+    } else if (a->type == VAR_INT ) { // replace at index a, length b, insert c
+        
+        assert_message(a || a->type == VAR_INT, "non-integer count");
+        assert_message(b || b->type == VAR_INT, "non-integer start");
+        replaced = byte_array_replace(self->str, c->str, a->integer, b->integer);
+        
+    } else exit_message("replacement is not a string");
+    
+    null_check(replaced);
+    struct variable *result = variable_new_str(context, replaced);
+    stack_push(context->operand_stack, result);
+}
+
+
+struct variable *builtin_method(struct Context *context, 
+                                struct variable *indexable,
+                                const struct variable *index)
+{
+    enum VarType it = indexable->type;
+    const char *idxstr = byte_array_to_string(index->str);
+
+    if (!strcmp(idxstr, FNC_LENGTH))
+        return variable_new_int(context, indexable->list->length);
+    if (!strcmp(idxstr, FNC_TYPE)) {
+        const char *typestr = var_type_str(it);
+        return variable_new_str(context, byte_array_from_string(typestr));
+    }
+
+    if (!strcmp(idxstr, FNC_STRING))
+        return variable_new_str(context, variable_value(context, indexable));
+
+    if (!strcmp(idxstr, FNC_LIST))
+        return variable_new_list(context, indexable->list);
+
+    if (!strcmp(idxstr, FNC_KEYS)) {
+        assert_message(it == VAR_LST || it == VAR_MAP, "keys are only for map or list");
+
+        struct variable *v = variable_new_list(context, array_new());
+        if (indexable->map) {
+            const struct array *a = map_keys(indexable->map);
+            for (int i=0; i<a->length; i++) {
+                struct variable *u = variable_new_str(context, (struct byte_array*)array_get(a, i));
+                array_add(v->list, u);
+            }
+        }
+        return v;
+    }
+
+    if (!strcmp(idxstr, FNC_VALUES)) {
+        assert_message(it == VAR_LST || it == VAR_MAP, "values are only for map or list");
+        if (!indexable->map)
+            return variable_new_list(context, array_new());
+        else
+            return variable_new_list(context, (struct array*)map_values(indexable->map));
+    }
+
+    if (!strcmp(idxstr, FNC_SERIALIZE)) {
+        struct byte_array *bits = variable_serialize(context, 0, indexable);
+        return variable_new_str(context, bits);
+    }
+
+    if (!strcmp(idxstr, FNC_DESERIALIZE)) {
+        struct byte_array *bits = indexable->str;
+        byte_array_reset(bits);
+        struct variable *d = variable_deserialize(context, bits);
+        return d;
+    }
+
+    if (!strcmp(idxstr, FNC_SORT)) {
+        assert_message(indexable->type == VAR_LST, "sorting non-list");
+        return variable_new_c(context, &cfnc_sort);
+    }
+
+    if (!strcmp(idxstr, FNC_FIND)) {
+        assert_message(indexable->type == VAR_STR, "searching in non-string");
+        return variable_new_c(context, &cfnc_find);
+    }
+
+    if (!strcmp(idxstr, FNC_PART))
+        return variable_new_c(context, &cfnc_part);
+
+    if (!strcmp(idxstr, FNC_REMOVE))
+        return variable_new_c(context, &cfnc_remove);
+
+    if (!strcmp(idxstr, FNC_INSERT))
+        return variable_new_c(context, &cfnc_insert);
+
+    if (!strcmp(idxstr, FNC_REPLACE))
+        return variable_new_c(context, &replace);
+
+    return NULL;
+}
diff -r 000000000000 -r 1a89e28dea91 sys.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/sys.h	Wed May 30 21:13:01 2012 +0000
@@ -0,0 +1,23 @@
+#ifndef SYS_H
+#define SYS_H
+
+#include "vm.h"
+
+void print();
+void save();
+void load();
+void rm();
+
+struct string_func
+{
+    const char* name;
+    bridge* func;
+};
+
+struct variable *func_map(struct Context *context);
+
+struct variable *builtin_method(struct Context *context,
+								struct variable *indexable,
+                                const struct variable *index);
+
+#endif // SYS_H
\ No newline at end of file
diff -r 000000000000 -r 1a89e28dea91 util.c
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/util.c	Wed May 30 21:13:01 2012 +0000
@@ -0,0 +1,203 @@
+#include "struct.h"
+#include "util.h"
+#include <string.h>
+#include <stdarg.h>
+
+#ifdef ANDROID
+#include <android/log.h>
+#define TAG "filagree"
+#endif
+
+#ifdef MBED
+
+#include "mbed.h"
+
+static Serial usbTxRx(USBTX, USBRX);
+
+size_t strnlen(char *s, size_t maxlen)
+{
+	size_t i;
+	for (i= 0; i<maxlen && *s; i++, s++);
+	return i;
+}
+
+char *strnstr(const char *s, const char *find, size_t slen)
+{
+	char c, sc;
+	size_t len;
+    
+	if ((c = *find++) != '\0') {
+		len = strlen(find);
+		do {
+			do {
+				if (slen-- < 1 || (sc = *s++) == '\0')
+					return (NULL);
+			} while (sc != c);
+			if (len > slen)
+				return (NULL);
+		} while (strncmp(s, find, len) != 0);
+		s--;
+	}
+	return ((char *)s);
+}
+
+#endif // MBED
+
+
+#define MESSAGE_MAX 100
+
+void log_print(const char *format, ...)
+{
+    static char log_message[MESSAGE_MAX+1] = "";
+    char one_line[MESSAGE_MAX];
+
+    char *newline;
+    va_list list;
+    va_start(list, format);
+    const char *message = make_message(format, list);
+    va_end(list);
+    size_t log_len = strnlen(log_message, MESSAGE_MAX);
+    strncat(log_message, message, MESSAGE_MAX - log_len);
+    log_len = strnlen(log_message, MESSAGE_MAX);
+    if (log_len == MESSAGE_MAX)
+        log_message[MESSAGE_MAX-1] = '\n';
+    if (!(newline = strnstr(log_message, "\n", MESSAGE_MAX)))
+        return;
+    size_t line_len = newline - log_message;
+    memcpy(one_line, log_message, line_len);
+    one_line[line_len] = 0;
+
+#ifdef ANDROID
+    __android_log_write(ANDROID_LOG_ERROR, TAG, one_line);
+#elifdef IOS
+    NSLog(@"%s", one_line);
+#elifdef MBED
+    usbTxRx.printf("%s\n", one_line);    
+#else
+    printf("%s\n", one_line);    
+#endif
+
+    memmove(log_message, newline+1, log_len-line_len);
+}
+
+const char *make_message(const char *format, va_list ap)
+{
+    static char message[MESSAGE_MAX];
+    vsnprintf(message, MESSAGE_MAX, format, ap);
+    return message;
+}
+
+void exit_message2(const char *format, va_list list)
+{
+    const char *message = make_message(format, list);
+    log_print("%s\n", message);
+    va_end(list);
+    exit(1);
+}
+
+void assert_message(bool assertion, const char *format, ...)
+{
+    if (assertion)
+        return;
+    va_list list;
+    va_start(list, format);
+    exit_message2(format, list);
+}
+
+void *exit_message(const char *format, ...)
+{
+    va_list list;
+    va_start(list, format);
+    exit_message2(format, list);
+    return NULL;
+}
+
+void null_check(const void *pointer) {
+    if (!pointer)
+        exit_message("null pointer");
+}
+
+const char* num_to_string(const struct number_string *ns, int num_items, int num)
+{
+    for (int i=0; i<num_items; i++) // reverse lookup nonterminal string
+        if (num == ns[i].number)
+            return ns[i].chars;
+    exit_message("num not found");
+    return NULL;
+}
+
+// file
+
+#define INPUT_MAX_LEN    10000
+#define ERROR_BIG        "Input file is too big"
+
+
+long fsize(FILE* file) {
+    if (!fseek(file, 0, SEEK_END)) {
+        long size = ftell(file);
+        if (size >= 0 && !fseek(file, 0, SEEK_SET))
+            return size;
+    }
+    return -1;
+}
+
+struct byte_array *read_file(const struct byte_array *filename_ba)
+{
+    FILE * file;
+    size_t read;
+    uint8_t *str;
+    long size;
+    
+    const char* filename_str = byte_array_to_string(filename_ba);
+
+    if (!(file = fopen(filename_str, "rb")))
+        exit_message(ERROR_FOPEN);
+    if ((size = fsize(file)) < 0)
+        exit_message(ERROR_FSIZE);
+    else if (size > INPUT_MAX_LEN)
+        exit_message(ERROR_BIG);
+    if (!(str = (uint8_t*)malloc((size_t)size)))// + 1)))
+        exit_message(ERROR_ALLOC);
+    
+    read = fread(str, 1, (size_t)size, file);
+    if (feof(file) || ferror(file))
+        exit_message(ERROR_FREAD);
+    
+    if (fclose(file))
+        exit_message(ERROR_FCLOSE);
+    
+    struct byte_array* ba = byte_array_new_size(read);
+    ba->data = str;
+    byte_array_reset(ba);
+    return ba;
+}
+
+int write_byte_array(struct byte_array* ba, FILE* file) {
+    uint16_t len = ba->length;
+    int n = fwrite(ba->data, 1, len, file);
+    return len - n;
+}
+
+int write_file(const struct byte_array* filename, struct byte_array* bytes)
+{
+    const char *fname = byte_array_to_string(filename);
+    FILE* file = fopen(fname, "w");
+    if (!file) {
+        DEBUGPRINT("could not open file %s\n", fname);
+        return -1;
+    }
+
+    int r = fwrite(bytes->data, 1, bytes->length, file);
+    DEBUGPRINT("\twrote %d bytes\n", r);
+    int s = fclose(file);
+    return (r<0) || s;
+}
+
+char* build_path(const char* dir, const char* name)
+{
+    int dirlen = dir ? strlen(dir) : 0;
+    char* path = (char*)malloc(dirlen + 1 + strlen(name));
+    const char* slash = (dir && dirlen && (dir[dirlen] != '/')) ? "/" : "";
+    sprintf(path, "%s%s%s", dir ? dir : "", slash, name);
+    return path;
+}
diff -r 000000000000 -r 1a89e28dea91 util.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/util.h	Wed May 30 21:13:01 2012 +0000
@@ -0,0 +1,65 @@
+#ifndef UTIL_H
+#define UTIL_H
+
+#include <stdbool.h>
+#include <setjmp.h>
+#include <stdint.h>
+#include <inttypes.h>
+#include <stdarg.h>
+#include <stdio.h>
+
+#ifdef __LP64__
+#define VOID_INT int64_t
+#define VOID_FLT long double
+#else
+#define VOID_INT int32_t
+#define VOID_FLT double)(int32_t
+#endif
+
+#define MBED
+#ifdef MBED
+#pragma diag_suppress 1293  //  suppress squeamish warning of "assignment in condition"
+#endif
+
+#define ARRAY_LEN(x) (sizeof x / sizeof *x)
+#define ITOA_LEN    19 // enough for 64-bit integer
+
+extern jmp_buf trying;
+const char *make_message(const char *fmt, va_list ap);
+void assert_message(bool assertion, const char *format, ...);
+void *exit_message(const char *format, ...);
+void null_check(const void* p);
+void log_print(const char *format, ...);
+
+#ifdef DEBUG
+#define DEBUGPRINT(...) log_print( __VA_ARGS__ );
+#else
+#define DEBUGPRINT(...) {};
+#endif // #ifdef DEBUG
+
+// file
+
+#define ERROR_FSIZE     "Could not get length of file"
+#define ERROR_FOPEN     "Could not open file"
+#define ERROR_FREAD     "Could not read file"
+#define ERROR_FCLOSE    "Could not close file"
+
+struct byte_array *read_file(const struct byte_array *filename);
+int write_file(const struct byte_array* filename, struct byte_array* bytes);
+long fsize(FILE* file);
+
+struct number_string {
+    uint8_t number;
+    char* chars;
+};
+
+const char* num_to_string(const struct number_string *ns, int num_items, int num);
+#define NUM_TO_STRING(ns, num) num_to_string(ns, ARRAY_LEN(ns), num)
+
+// error messages
+
+#define ERROR_ALLOC        "Could not allocate memory"
+
+
+
+#endif // UTIL_H
diff -r 000000000000 -r 1a89e28dea91 variable.c
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/variable.c	Wed May 30 21:13:01 2012 +0000
@@ -0,0 +1,334 @@
+#include <string.h>
+/*#include <stdio.h>
+#include <signal.h>
+#include <stdarg.h>
+#include <time.h>
+#include "util.h"
+#include "sys.h"
+*/
+#include "vm.h"
+#include "struct.h"
+#include "serial.h"
+#include "variable.h"
+#include "util.h"
+
+#define    ERROR_VAR_TYPE    "type error"
+#define VAR_MAX    100
+
+const struct number_string var_types[] = {
+    {VAR_NIL,        "nil"},
+    {VAR_INT,        "integer"},
+    {VAR_BOOL,        "boolean"},
+    {VAR_FLT,        "float"},
+    {VAR_STR,        "string"},
+    {VAR_LST,        "list"},
+    {VAR_FNC,        "function"},
+    {VAR_MAP,        "map"},
+    {VAR_ERR,        "error"},
+    {VAR_C,            "c-function"},
+};
+
+const char *var_type_str(enum VarType vt)
+{
+    return NUM_TO_STRING(var_types, vt);
+}
+
+struct variable* variable_new(struct Context *context, enum VarType type)
+{
+	null_check(context);
+   if (context->num_vars++ > VAR_MAX)
+        garbage_collect(context);
+    struct variable* v = (struct variable*)malloc(sizeof(struct variable));
+    v->type = type;
+    v->map = NULL;
+    v->marked = false;
+    return v;
+}
+
+struct variable* variable_new_err(struct Context *context, const char* message)
+{
+	null_check(context);
+    struct variable *v = variable_new(context, VAR_ERR);
+    v->str = byte_array_from_string(message);
+    return v;
+}
+
+struct variable* variable_new_nil(struct Context *context)
+{
+	null_check(context);
+    return variable_new(context, VAR_NIL);
+}
+
+struct variable* variable_new_int(struct Context *context, int32_t i)
+{
+	null_check(context);
+    struct variable *v = variable_new(context, VAR_INT);
+    v->integer = i;
+    return v;
+}
+
+struct variable* variable_new_bool(struct Context *context, bool b)
+{
+	null_check(context);
+    struct variable *v = variable_new(context, VAR_BOOL);
+    v->boolean = b;
+    return v;
+}
+
+void variable_del(struct Context *context, struct variable *v)
+{
+	null_check(context);
+    context->num_vars--;
+    switch (v->type) {
+        case VAR_INT:
+        case VAR_FLT:
+        case VAR_MAP:
+            break;
+        case VAR_STR:
+        case VAR_FNC:
+            byte_array_del(v->str);
+            break;
+        case VAR_LST:
+            for (int i=0; i<v->list->length; i++)
+                variable_del(context, (struct variable*)array_get(v->list, i));
+            break;
+        default:
+            vm_exit_message(context, "bad var type");
+            break;
+    }
+    if (v->map) {
+        struct array *keys = map_keys(v->map);
+        struct array *values = map_values(v->map);
+        for (int i=0; i<keys->length; i++) {
+            byte_array_del((struct byte_array*)array_get(keys, i));
+            variable_del(context, (struct variable*)array_get(values, i));
+        }
+        array_del(keys);
+        array_del(values);
+        map_del(v->map);
+    }
+    free(v);
+}
+
+struct variable* variable_new_float(struct Context *context, float f)
+{
+	null_check(context);
+    //DEBUGPRINT("new float %f\n", f);
+    struct variable *v = variable_new(context, VAR_FLT);
+    v->floater = f;
+    return v;
+}
+
+struct variable *variable_new_str(struct Context *context, struct byte_array *str) {
+    struct variable *v = variable_new(context, VAR_STR);
+    v->str = str;
+    return v;
+}
+
+struct variable *variable_new_fnc(struct Context *context, struct byte_array *fnc) {
+    struct variable *v = variable_new(context, VAR_FNC);
+    v->str = fnc;
+    return v;
+}
+
+struct variable *variable_new_list(struct Context *context, struct array *list) {
+    struct variable *v = variable_new(context, VAR_LST);
+    v->list = list ? list : array_new();
+    return v;
+}
+
+struct variable *variable_new_map(struct Context *context, struct map *map) {
+    struct variable *v = variable_new(context, VAR_MAP);
+    v->map = map;
+    return v;
+}
+
+struct variable *variable_new_c(struct Context *context, bridge *cfnc) {
+    struct variable *v = variable_new(context, VAR_C);
+    v->cfnc = cfnc;
+    return v;
+}
+
+const char *variable_value_str(struct Context *context, const struct variable* v)
+{
+	null_check(v);
+    char* str = (char*)malloc(100);
+    struct array* list = v->list;
+	
+    enum VarType vt = (enum VarType)v->type;
+    switch (vt) {
+        case VAR_NIL:    sprintf(str, "nil");                                    break;
+        case VAR_INT:    sprintf(str, "%d", v->integer);                         break;
+        case VAR_BOOL:   sprintf(str, "%s", v->boolean ? "true" : "false");      break;
+        case VAR_FLT:    sprintf(str, "%f", v->floater);                         break;
+        case VAR_STR:    sprintf(str, "%s", byte_array_to_string(v->str));       break;
+        case VAR_FNC:    sprintf(str, "f(%dB)", v->str->length);                 break;
+        case VAR_C:      sprintf(str, "c-function");                             break;
+        case VAR_MAP:                                                            break;
+        case VAR_LST: {
+            strcpy(str, "[");
+            vm_null_check(context, list);
+            for (int i=0; i<list->length; i++) {
+                struct variable* element = (struct variable*)array_get(list, i);
+                vm_null_check(context, element);
+                const char *q = (element->type == VAR_STR || element->type == VAR_FNC) ? "'" : "";
+                const char *c = i ? "," : "";
+				const char *estr = variable_value_str(context, element);
+                sprintf(str, "%s%s%s%s%s", str, c, q, estr, q);
+            }
+        } break;
+        case VAR_ERR:
+            strcpy(str, byte_array_to_string(v->str));
+            break;
+        default:
+            vm_exit_message(context, ERROR_VAR_TYPE);
+            break;
+    }
+
+    if (v->map) {
+        const struct array *a = map_keys(v->map);
+        const struct array *b = map_values(v->map);
+		
+        if (vt != VAR_LST)
+            strcat(str, "[");
+        else if (v->list->length && a->length)
+            strcat(str, ",");
+        for (int i=0; i<a->length; i++) {
+            if (i)
+                strcat(str, ",");
+            strcat(str, "'");
+            strcat(str, byte_array_to_string((struct byte_array*)array_get(a,i)));
+            strcat(str, "'");
+            strcat(str, ":");
+			const struct variable *biv = (const struct variable*)array_get(b,i);
+			const char *bistr = variable_value_str(context, biv);
+            strcat(str, bistr);
+        }
+        strcat(str, "]");
+    }
+    else if (vt == VAR_LST)
+        strcat(str, "]");
+
+	return str;
+}
+
+struct byte_array *variable_value(struct Context *c, const struct variable *v) {
+	const char *str = variable_value_str(c, v);
+    return byte_array_from_string(str);
+}
+
+
+
+struct variable *variable_pop(struct Context *context)
+{
+	null_check(context);
+    struct variable *v = (struct variable*)stack_pop(context->operand_stack);
+    //DEBUGPRINT("\nvariable_pop\n");// %s\n", variable_value(v));
+    //    print_operand_stack();
+    return v;
+}
+
+void variable_push(struct Context *context, struct variable *v)
+{
+	null_check(context);
+    stack_push(context->operand_stack, v);
+    //DEBUGPRINT("\nvariable_push\n");
+    //print_operand_stack();
+}
+
+struct byte_array *variable_serialize(struct Context *context, 
+									  struct byte_array *bits,
+                                      const struct variable *in)
+{
+	null_check(context);
+    //DEBUGPRINT("\tserialize:%s\n", variable_value(in));
+    if (!bits)
+        bits = byte_array_new();
+    serial_encode_int(bits, 0, in->type);
+    switch (in->type) {
+        case VAR_INT:    serial_encode_int(bits, 0, in->integer);    break;
+        case VAR_FLT:    serial_encode_float(bits, 0, in->floater);    break;
+        case VAR_STR:
+        case VAR_FNC:    serial_encode_string(bits, 0, in->str);        break;
+        case VAR_LST: {
+            serial_encode_int(bits, 0, in->list->length);
+            for (int i=0; i<in->list->length; i++)
+                variable_serialize(context, bits, (const struct variable*)array_get(in->list, i));
+            if (in->map) {
+                const struct array *keys = map_keys(in->map);
+                const struct array *values = map_values(in->map);
+                serial_encode_int(bits, 0, keys->length);
+                for (int i=0; i<keys->length; i++) {
+                    serial_encode_string(bits, 0, (const struct byte_array*)array_get(keys, i));
+                    variable_serialize(context, bits, (const struct variable*)array_get(values, i));
+                }
+            } else
+                serial_encode_int(bits, 0, 0);
+        } break;
+        case VAR_MAP:                                                break;
+        default:        vm_exit_message(context, "bad var type");                break;
+    }
+	
+    //DEBUGPRINT("in: %s\n", variable_value(in));
+    //byte_array_print("serialized: ", bits);
+    return bits;
+}
+
+struct variable *variable_deserialize(struct Context *context, struct byte_array *bits)
+{
+	null_check(context);
+    enum VarType vt = (enum VarType)serial_decode_int(bits);
+    switch (vt) {
+        case VAR_NIL:    return variable_new_nil(context);
+        case VAR_INT:    return variable_new_int(context, serial_decode_int(bits));
+        case VAR_FLT:    return variable_new_float(context, serial_decode_float(bits));
+        case VAR_FNC:    return variable_new_fnc(context, serial_decode_string(bits));
+        case VAR_STR:    return variable_new_str(context, serial_decode_string(bits));
+        case VAR_LST: {
+            uint32_t size = serial_decode_int(bits);
+            struct array *list = array_new_size(size);
+            while (size--)
+                array_add(list, variable_deserialize(context, bits));
+            struct variable *out = variable_new_list(context, list);
+			
+            uint32_t map_length = serial_decode_int(bits);
+            if (map_length) {
+                out->map = map_new();
+                for (int i=0; i<map_length; i++) {
+                    struct byte_array *key = serial_decode_string(bits);
+                    struct variable *value = variable_deserialize(context, bits);
+                    map_insert(out->map, key, value);
+                }
+            }
+            return out;
+        }
+        default:
+            vm_exit_message(context, "bad var type");
+            return NULL;
+    }
+}
+
+int variable_save(struct Context *context, 
+				  const struct variable *v,
+                  const struct variable *path)
+{
+    vm_null_check(context, v);
+    vm_null_check(context, path);
+	
+    struct byte_array *bytes = byte_array_new();
+    variable_serialize(context, bytes, v);
+    return write_file(path->str, bytes);
+}
+
+struct variable *variable_load(struct Context *context, const struct variable *path)
+{
+	null_check(context);
+    vm_null_check(context, path);
+	
+    struct byte_array *file_bytes = read_file(path->str);
+    if (!file_bytes)
+        return NULL;
+    struct variable *v = variable_deserialize(context, file_bytes);
+    return v;
+}
+
diff -r 000000000000 -r 1a89e28dea91 variable.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/variable.h	Wed May 30 21:13:01 2012 +0000
@@ -0,0 +1,63 @@
+#ifndef VARIABLE_H
+#define VARIABLE_H
+
+//#include "vm.h"
+
+enum VarType {
+    VAR_NIL,
+    VAR_INT,
+    VAR_FLT,
+    VAR_BOOL,
+    VAR_STR,
+    VAR_FNC,
+    VAR_LST,
+    VAR_MAP,
+    VAR_ERR,
+    VAR_C,
+};    
+
+typedef struct Context *context_p; // forward declaration
+typedef void(bridge)(context_p context);
+
+struct variable {
+    const struct byte_array* name;
+    enum VarType type;
+    uint8_t marked;
+    union {
+        struct byte_array* str;
+        struct array *list;
+        int32_t integer;
+        float floater;
+        bool boolean;
+        void(*cfnc)(context_p); // i.e., bridge
+    };
+    struct map *map;
+};
+
+struct variable* variable_new(struct Context *context, enum VarType type);
+void variable_del(struct Context *context, struct variable *v);
+struct byte_array* variable_value(struct Context *context, const struct variable* v);
+const char* variable_value_str(struct Context *context, const struct variable* v);
+struct byte_array *variable_serialize(struct Context *context, struct byte_array *bits,
+                                      const struct variable *in);
+struct variable *variable_deserialize(struct Context *context, struct byte_array *str);
+extern int variable_save(struct Context *context, const struct variable* v, const struct variable* path);
+extern struct variable *variable_load(struct Context *context, const struct variable* path);
+
+struct variable* variable_new_bool(struct Context *context, bool b);
+struct variable *variable_new_err(struct Context *context, const char* message);
+struct variable *variable_new_c(struct Context *context, bridge *cfnc);
+struct variable *variable_new_int(struct Context *context, int32_t i);
+struct variable *variable_new_nil(struct Context *context);
+struct variable *variable_new_map(struct Context *context, struct map *map);
+struct variable *variable_new_float(struct Context *context, float f);
+struct variable *variable_new_str(struct Context *context, struct byte_array *str);
+struct variable *variable_new_fnc(struct Context *context, struct byte_array *fnc);
+struct variable *variable_new_list(struct Context *context, struct array *list);
+struct variable* variable_copy(struct Context *context, const struct variable* v);
+struct variable *variable_pop(struct Context *context);
+void variable_push(struct Context *context, struct variable *v);
+
+const char *var_type_str(enum VarType vt);
+
+#endif // VARIABLE_H
diff -r 000000000000 -r 1a89e28dea91 vm.c
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/vm.c	Wed May 30 21:13:01 2012 +0000
@@ -0,0 +1,1108 @@
+#include <stdio.h>
+#include <signal.h>
+#include <string.h>
+#include <stdarg.h>
+#include <time.h>
+#include "util.h"
+#include "serial.h"
+#include "vm.h"
+#include "variable.h"
+#include "sys.h"
+
+#define VM_NAME "vm"
+
+struct variable *run(struct Context *context, struct byte_array *program, bool in_context);
+struct variable *rhs_pop(struct Context *context);
+static void dst(struct Context *context);
+void src_size(struct Context *context, int32_t size);
+void display_code(struct Context *context, struct byte_array *code);
+
+
+#ifdef DEBUG
+
+#define VM_DEBUGPRINT(...) DEBUGPRINT(__VA_ARGS__ ); if (!context->runtime) return;
+
+void print_operand_stack();
+
+#define INDENT context->indent++;
+#define UNDENT context->indent--;
+
+#else // not DEBUG
+
+#define INDENT
+#define UNDENT
+
+#define VM_DEBUGPRINT(...)
+
+#endif // not DEBUG
+
+
+// assertions //////////////////////////////////////////////////////////////
+
+jmp_buf trying;
+
+static void vm_exit() {
+    longjmp(trying, 1);
+}
+
+void set_error(struct Context *context, const char *format, va_list list)
+{
+    if (!context)
+        return;
+    null_check(format);
+    const char *message = make_message(format, list);
+    context->error = variable_new_err(context, message);
+}
+
+void *vm_exit_message(struct Context *context, const char *format, ...)
+{
+    // make error variable
+    va_list list;
+    va_start(list, format);
+    set_error(context, format, list);
+    va_end(list);
+
+    vm_exit();
+    return NULL;
+}
+
+void vm_assert(struct Context *context, bool assertion, const char *format, ...)
+{
+    if (!assertion) {
+
+        // make error variable
+        va_list list;
+        va_start(list, format);
+        set_error(context, format, list);
+        va_end(list);
+
+        vm_exit();
+    }
+}
+
+void vm_null_check(struct Context *context, const void* p) {
+    vm_assert(context, p, "null pointer");
+}
+
+// state ///////////////////////////////////////////////////////////////////
+
+struct program_state {
+    //    struct byte_array *code;
+    struct map *named_variables;
+    struct array *all_variables;
+    uint32_t pc;
+};
+
+struct program_state *program_state_new(struct Context *context)
+{
+    null_check(context);
+    struct program_state *state = (struct program_state*)malloc(sizeof(struct program_state));
+    state->named_variables = map_new();
+    state->all_variables = array_new();
+    stack_push(context->program_stack, state);
+    return state;
+}
+
+struct Context *vm_init()
+{
+    struct Context *context = (struct Context*)malloc(sizeof(struct Context));
+    null_check(context);
+    context->program_stack = stack_new();
+    context->operand_stack = stack_new();
+    context->vm_exception = NULL;
+    context->runtime = true;
+    context->num_vars = 0;
+	context->rhs = stack_new();
+
+	struct variable *vm_var = func_map(context);
+	context->vm_state = program_state_new(context);
+	map_insert(context->vm_state->named_variables, byte_array_from_string(VM_NAME), vm_var);
+
+    return context;
+}
+
+// garbage collection //////////////////////////////////////////////////////
+
+void mark(struct Context *context, struct variable *root)
+{
+    null_check(context);
+    if (root->map) {
+        const struct array *values = map_values(root->map);
+        for (int i=0; values && i<values->length; i++)
+            mark(context, (struct variable*)array_get(values, i));
+    }
+
+    root->marked = true;
+    switch (root->type) {
+        case VAR_INT:
+        case VAR_FLT:
+        case VAR_STR:
+        case VAR_FNC:
+        case VAR_MAP:
+            break;
+        case VAR_LST:
+            for (int i=0; i<root->list->length; i++)
+                mark(context, (struct variable*)array_get(root->list, i));
+            break;
+        default:
+            vm_exit_message(context, "bad var type");
+            break;
+    }
+}
+
+void sweep(struct Context *context, struct variable *root)
+{
+    null_check(context);
+    struct program_state *state = (struct program_state*)stack_peek(context->program_stack, 0);
+    struct array *vars = state->all_variables; 
+    for (int i=0; i<vars->length; i++) {
+        struct variable *v = (struct variable*)array_get(vars, i);
+        if (!v->marked)
+            variable_del(context, v);
+        else
+            v->marked = false;
+    }
+}
+
+void garbage_collect(struct Context *context)
+{
+    null_check(context);
+    struct program_state *state = (struct program_state*)stack_peek(context->program_stack, 0);
+    struct array *vars = state->all_variables; 
+    for (int i=0; i<vars->length; i++) {
+        struct variable *v = (struct variable*)array_get(vars, i);
+        mark(context, v);
+        sweep(context, v);
+    }
+}
+
+// display /////////////////////////////////////////////////////////////////
+
+#ifdef DEBUG
+
+const struct number_string opcodes[] = {
+    {VM_NIL,        "NIL"},
+    {VM_INT,        "INT"},
+    {VM_BOOL,       "BUL"},
+    {VM_FLT,        "FLT"},
+    {VM_STR,        "STR"},
+    {VM_VAR,        "VAR"},
+    {VM_FNC,        "FNC"},
+    {VM_SRC,        "SRC"},
+    {VM_LST,        "LST"},
+    {VM_DST,        "DST"},
+    {VM_MAP,        "MAP"},
+    {VM_GET,        "GET"},
+    {VM_PUT,        "PUT"},
+    {VM_ADD,        "ADD"},
+    {VM_SUB,        "SUB"},
+    {VM_MUL,        "MUL"},
+    {VM_DIV,        "DIV"},
+    {VM_MOD,        "MOD"},
+    {VM_AND,        "AND"},
+    {VM_OR,         "ORR"},
+    {VM_NOT,        "NOT"},
+    {VM_NEG,        "NEG"},
+    {VM_EQU,        "EQU"},
+    {VM_NEQ,        "NEQ"},
+    {VM_GTN,        "GTN"},
+    {VM_LTN,        "LTN"},
+    {VM_IFF,        "IFF"},
+    {VM_JMP,        "JMP"},
+    {VM_CAL,        "CAL"},
+    {VM_MET,        "MET"},
+    {VM_RET,        "RET"},
+    {VM_ITR,        "ITR"},
+    {VM_COM,        "COM"},
+    {VM_TRY,        "TRY"},
+};
+
+void print_operand_stack(struct Context *context)
+{
+    null_check(context);
+    struct variable *operand;
+    for (int i=0; (operand = stack_peek(context->operand_stack, i)); i++)
+        DEBUGPRINT("\t%s\n", variable_value_str(context, operand));
+}
+
+const char* indentation(struct Context *context)
+{
+    null_check(context);
+    static char str[100];
+    int tab = 0;
+    while (tab < context->indent)
+        str[tab++] = '\t';
+    str[tab] = 0;
+    return (const char*)str;
+}
+
+static void display_program_counter(struct Context *context, const struct byte_array *program)
+{
+    null_check(context);
+    DEBUGPRINT("%s%2ld:%3d ", indentation(context), program->current-program->data, *program->current);
+}
+
+void display_code(struct Context *context, struct byte_array *code)
+{
+    null_check(context);
+    bool was_running = context->runtime;
+    context->runtime = false;
+
+    INDENT
+    run(context, code, false);
+    UNDENT
+
+    context->runtime = was_running;
+}
+
+void display_program(struct byte_array *program)
+{
+    struct Context *context = vm_init();
+
+    INDENT
+    DEBUGPRINT("%sprogram bytes:\n", indentation(context));
+
+    INDENT
+    for (int i=0; i<program->length; i++)
+        DEBUGPRINT("%s%2d:%3d\n", indentation(context), i, program->data[i]);
+    UNDENT
+
+    DEBUGPRINT("%sprogram instructions:\n", indentation(context));
+    byte_array_reset(program);
+    struct byte_array* code = serial_decode_string(program);
+
+    display_code(context, code);
+
+    UNDENT
+    UNDENT
+}
+
+#else // not DEBUG
+
+void display_code(struct Context *context, struct byte_array *code) {}
+const char* indentation(struct Context *context) { return ""; }
+
+#endif // DEBUG
+
+// instruction implementations /////////////////////////////////////////////
+
+void src_size(struct Context *context, int32_t size)
+{
+    null_check(context);
+    if (size > 1)
+        while (stack_peek(context->rhs,1))
+            stack_pop(context->rhs);
+    else if (!stack_empty(context->rhs))
+        return;
+
+    while (size--)
+        stack_push(context->rhs, variable_pop(context));
+}
+
+static void src(struct Context *context, enum Opcode op, struct byte_array *program)
+{
+    null_check(context);
+    int32_t size = serial_decode_int(program);
+    VM_DEBUGPRINT("%s %d\n", NUM_TO_STRING(opcodes, op), size);
+    src_size(context, size);
+}
+
+void vm_call(struct Context *context)
+{
+    null_check(context);
+    // get the function pointer from the stack
+    struct variable *func = variable_pop(context);
+    INDENT
+
+    // call the function
+    switch (func->type) {
+        case VAR_FNC:
+            run(context, func->str, false);
+            break;
+        case VAR_C:
+            func->cfnc(context);
+            break;
+        default:
+            vm_exit_message(context, "not a function");
+            break;
+    }
+    UNDENT
+}
+
+static inline void func_call(struct Context *context)
+{
+    null_check(context);
+    VM_DEBUGPRINT("VM_CAL\n");
+    vm_call(context);
+}
+
+static void push_list(struct Context *context, struct byte_array *program)
+{
+    null_check(context);
+    int32_t num_items = serial_decode_int(program);
+    DEBUGPRINT("LST %d", num_items);
+    if (!context->runtime)
+        VM_DEBUGPRINT("\n");
+    struct array *items = array_new();
+    struct map *map = map_new(); 
+
+    while (num_items--) {
+        struct variable* v = variable_pop(context);
+        if (v->type == VAR_MAP)
+            map_update(map, v->map); // mapped values are stored in the map, not list
+        else
+            array_insert(items, 0, v);
+    }
+    struct variable *list = variable_new_list(context, items);
+    list->map = map;
+    DEBUGPRINT(": %s\n", variable_value_str(context, list));
+    variable_push(context, list);
+}
+
+static void push_map(struct Context *context, struct byte_array *program)
+{
+    null_check(context);
+    int32_t num_items = serial_decode_int(program);
+    DEBUGPRINT("MAP %d", num_items);
+    if (!context->runtime)
+        VM_DEBUGPRINT("\n");
+    struct map *map = map_new();
+    while (num_items--) {
+        struct variable* value = variable_pop(context);
+        struct variable* key = variable_pop(context);
+        assert_message(key->type==VAR_STR, "non-string map index");
+        map_insert(map, key->str, value);
+    }
+    struct variable *v = variable_new_map(context, map);
+    DEBUGPRINT(": %s\n", variable_value_str(context, v));
+    variable_push(context, v);
+}
+
+struct variable* variable_set(struct Context *context, struct variable *u, const struct variable* v)
+{
+    null_check(context);
+    vm_null_check(context, u);
+    vm_null_check(context, v);
+    switch (v->type) {
+        case VAR_NIL:                                        break;
+        case VAR_INT:    u->integer = v->integer;            break;
+        case VAR_FLT:    u->floater = v->floater;            break;
+        case VAR_FNC:
+        case VAR_STR:    u->str = byte_array_copy(v->str);   break;
+        case VAR_LST:
+            u->list = v->list;
+            u->list->current = u->list->data;                break;
+        default:
+            vm_exit_message(context, "bad var type");
+            break;
+    }
+    if (v->type == VAR_STR)
+        u->str = byte_array_copy(v->str);
+    u->map = v->map;
+    return u;
+}
+
+struct variable* variable_copy(struct Context *context, const struct variable* v)
+{
+    null_check(context);
+    vm_null_check(context, v);
+    struct variable *u = variable_new(context, (enum VarType)v->type);
+    variable_set(context, u, v);
+    return u;
+}
+
+
+// run /////////////////////////////////////////////////////////////////////
+
+static struct variable *list_get_int(struct Context *context,
+                                     const struct variable *indexable,
+                                     const struct variable *index)
+{
+    null_check(context);
+    null_check(indexable);
+    null_check(index);
+
+    uint32_t n = index->integer;
+    enum VarType it = (enum VarType)indexable->type;
+    switch (it) {
+        case VAR_LST:
+            return (struct variable*)array_get(indexable->list, n);
+        case VAR_STR: {
+            vm_assert(context, n<indexable->str->length, "index out of bounds");
+            char *str = (char*)malloc(2);
+            sprintf(str, "%c", indexable->str->data[n]);
+            return variable_new_str(context, byte_array_from_string(str));
+        }
+        default:
+            vm_exit_message(context, "indexing non-indexable");
+            return NULL;
+    }
+}
+
+void lookup(struct Context *context, struct variable *indexable, struct variable *index)
+{
+    null_check(context);
+    if (!context->runtime)
+        VM_DEBUGPRINT("GET\n");
+
+    struct variable *item=0;
+
+    switch (index->type) {
+        case VAR_INT:
+            item = list_get_int(context, indexable, index);
+            break;
+        case VAR_STR:
+            if (indexable->map)
+                item = (struct variable*)map_get(indexable->map, index->str);
+            if (!item)
+                item = builtin_method(context, indexable, index);
+            assert_message(item, "did not find member");
+            break;
+        default:
+            vm_exit_message(context, "bad index type");
+            break;
+    }
+    DEBUGPRINT("%s\n", variable_value_str(context, item));
+    variable_push(context, item);
+}
+
+static void list_get(struct Context *context)
+{
+    null_check(context);
+    DEBUGPRINT("GET ");
+    if (!context->runtime)
+        VM_DEBUGPRINT("\n");
+    struct variable *indexable, *index;
+    indexable = variable_pop(context);
+    index = variable_pop(context);
+    lookup(context, indexable, index);
+}
+
+static void method(struct Context *context, struct byte_array *program)
+{
+    null_check(context);
+    DEBUGPRINT("MET ");
+    if (!context->runtime)
+        VM_DEBUGPRINT("\n");
+    struct variable *indexable, *index;
+    indexable = variable_pop(context);
+    index = variable_pop(context);
+    lookup(context, indexable, index);
+    stack_push(context->rhs, indexable);
+    vm_call(context);
+}
+
+
+static int32_t jump(struct Context *context, struct byte_array *program)
+{
+    null_check(context);
+    null_check(program);
+    uint8_t *start = program->current;
+    int32_t offset = serial_decode_int(program);
+    DEBUGPRINT("JMP %d\n", offset);
+    if (!context->runtime)
+        return 0;
+
+    return offset - (program->current - start);
+}
+
+bool test_operand(struct Context *context)
+{
+    null_check(context);
+    struct variable* v = variable_pop(context);
+    bool indeed = false;
+    switch (v->type) {
+        case VAR_NIL:   indeed = false;                     break;
+        case VAR_BOOL:  indeed = v->boolean;                break;
+        case VAR_INT:   indeed = v->integer;                break;
+        default:
+            vm_exit_message(context, "bad iff operand");
+            break;
+    }
+    return indeed;
+}
+
+static int32_t iff(struct Context *context, struct byte_array *program)
+{
+    null_check(context);
+    null_check(program);
+    int32_t offset = serial_decode_int(program);
+    DEBUGPRINT("IF %d\n", offset);
+    if (!context->runtime)
+        return 0;
+    return test_operand(context) ? 0 : (VOID_INT)offset;
+}
+
+static void push_nil(struct Context *context)
+{
+    null_check(context);
+    struct variable* var = variable_new_nil(context);
+    VM_DEBUGPRINT("NIL\n");
+    variable_push(context, var);
+}
+
+static void push_int(struct Context *context, struct byte_array *program)
+{
+    null_check(context);
+    null_check(program);
+    int32_t num = serial_decode_int(program);
+    VM_DEBUGPRINT("INT %d\n", num);
+    struct variable* var = variable_new_int(context, num);
+    variable_push(context, var);
+}
+
+static void push_bool(struct Context *context, struct byte_array *program)
+{
+    null_check(context);
+    null_check(program);
+    int32_t num = serial_decode_int(program);
+    VM_DEBUGPRINT("BOOL %d\n", num);
+    struct variable* var = variable_new_bool(context, num);
+    variable_push(context, var);
+}
+
+static void push_float(struct Context *context, struct byte_array *program)
+{
+    null_check(context);
+    null_check(program);
+    float num = serial_decode_float(program);
+    VM_DEBUGPRINT("FLT %f\n", num);
+    struct variable* var = variable_new_float(context, num);
+    variable_push(context, var);
+}
+
+struct variable *find_var(struct Context *context, const struct byte_array *name)
+{
+    null_check(context);
+    null_check(name);
+    const struct program_state *state = (const struct program_state*)stack_peek(context->program_stack, 0);
+    struct map *var_map = state->named_variables;
+    struct variable *v = (struct variable*)map_get(var_map, name);
+    //DEBUGPRINT("find_var(%s) in %p,%p = %p\n", byte_array_to_string(name), state, var_map, v);
+    if (!v)
+        v = (struct variable*)map_get(context->vm_state->named_variables, name);
+    return v;
+}
+
+static void push_var(struct Context *context, struct byte_array *program)
+{
+    struct byte_array* name = serial_decode_string(program);
+    VM_DEBUGPRINT("VAR %s\n", byte_array_to_string(name));
+    struct variable *v = find_var(context, name);
+    vm_assert(context, v, "variable %s not found", byte_array_to_string(name));
+    variable_push(context, v);
+}
+
+static void push_str(struct Context *context, struct byte_array *program)
+{
+    struct byte_array* str = serial_decode_string(program);
+    VM_DEBUGPRINT("STR '%s'\n", byte_array_to_string(str));
+    struct variable* v = variable_new_str(context, str);
+    variable_push(context, v);
+}
+
+static void push_fnc(struct Context *context, struct byte_array *program)
+{
+    uint32_t fcodelen = serial_decode_int(program);
+    struct byte_array* fbody = byte_array_new_size(fcodelen);
+    memcpy(fbody->data, program->current, fcodelen);
+
+    DEBUGPRINT("FNC %u\n", fcodelen);
+    display_code(context, fbody);
+
+    if (context->runtime) {
+        struct variable* var = variable_new_fnc(context, (struct byte_array*)fbody);
+        variable_push(context, var);
+    }
+
+    program->current += fcodelen;
+}
+
+void set_named_variable(struct Context *context, 
+                        struct program_state *state,
+                        const struct byte_array *name,
+                        const struct variable *value)
+{
+    if (!state)
+        state = (struct program_state*)stack_peek(context->program_stack, 0);
+    struct map *var_map = state->named_variables;
+    struct variable *to_var = find_var(context, name);
+
+    if (!to_var) { // new variable
+        to_var = variable_copy(context, value);
+        to_var->name = byte_array_copy(name);
+    } else
+        variable_set(context, to_var, value);
+
+    map_insert(var_map, name, to_var);
+
+    //DEBUGPRINT(" (SET %s to %s in {%p,%p,%p})\n", byte_array_to_string(name), variable_value(to_var), state, var_map, to_var);
+}
+
+struct variable *rhs_pop(struct Context *context)
+{
+    struct variable *value = (struct variable*)stack_pop(context->rhs);
+    if (!value)
+        value = variable_new_nil(context);
+    return value;
+}
+
+static void set(struct Context *context, struct program_state *state, struct byte_array *program)
+{
+    null_check(context);
+    struct byte_array *name = serial_decode_string(program);    // destination variable name
+    if (!context->runtime)
+        VM_DEBUGPRINT("SET %s\n", byte_array_to_string(name));
+
+    struct variable *value = rhs_pop(context);
+    DEBUGPRINT("SET %s to %s\n", byte_array_to_string(name), variable_value_str(context, value));
+    set_named_variable(context, state, name, value); // set the variable to the value
+}
+
+static void dst(struct Context *context)
+{
+    VM_DEBUGPRINT("DST\n");
+    while (!stack_empty(context->rhs))
+        stack_pop(context->rhs);
+}
+
+static void list_put(struct Context *context)
+{
+    DEBUGPRINT("PUT");
+    if (!context->runtime)
+        VM_DEBUGPRINT("\n");
+    struct variable* recipient = variable_pop(context);
+    struct variable* key = variable_pop(context);
+    struct variable *value = rhs_pop(context);
+
+    switch (key->type) {
+        case VAR_INT:
+            switch (recipient->type) {
+                case VAR_LST:
+                    array_set(recipient->list, key->integer, value);
+                    break;
+                case VAR_STR:
+                    ((uint8_t*)recipient->str)[key->integer] = (uint8_t)value->integer;
+                    break;
+                default:
+                    vm_exit_message(context, "indexing non-indexable");
+            } break;
+        case VAR_STR:
+            if (!recipient->map)
+                recipient->map = map_new();
+            map_insert(recipient->map, key->str, value);
+            break;
+        default:
+            vm_exit_message(context, "bad index type");
+            break;
+    }
+    DEBUGPRINT(": %s\n", variable_value_str(context, recipient));
+}
+
+static struct variable *binary_op_int(struct Context *context,
+                                      enum Opcode op,
+                                      const struct variable *u,
+                                      const struct variable *v)
+{
+    int32_t m = u->integer;
+    int32_t n = v->integer;
+    int32_t i;
+    switch (op) {
+        case VM_MUL:    i = m * n;    break;
+        case VM_DIV:    i = m / n;    break;
+        case VM_ADD:    i = m + n;    break;
+        case VM_SUB:    i = m - n;    break;
+        case VM_AND:    i = m && n;   break;
+        case VM_EQU:    i = m == n;   break;
+        case VM_OR:     i = m || n;   break;
+        case VM_GTN:    i = m > n;    break;
+        case VM_LTN:    i = m < n;    break;
+        case VM_BND:    i = m & n;    break;
+        case VM_BOR:    i = m | n;    break;
+        case VM_MOD:    i = m % n;    break;
+        case VM_XOR:    i = m ^ n;    break;
+        case VM_RSF:    i = m >> n;   break;
+        case VM_LSF:    i = m << n;   break;
+
+        default:
+            return (struct variable*)vm_exit_message(context, "bad math int operator");
+    }
+    return variable_new_int(context, i);
+}
+
+static struct variable *binary_op_float(struct Context *context,
+                                        enum Opcode op,
+                                        const struct variable *u,
+                                        const struct variable *v)
+{
+    float m = u->floater;
+    float n = v->floater;
+    float f = 0;
+    switch (op) {
+        case VM_MUL:    f = m * n;                            break;
+        case VM_DIV:    f = m / n;                            break;
+        case VM_ADD:    f = m + n;                            break;
+        case VM_SUB:    f = m - n;                            break;
+        case VM_NEQ:    f = m != n;                            break;
+        case VM_GTN:    return variable_new_int(context, n > m);
+        case VM_LTN:    return variable_new_int(context, n < m);
+        default:
+            return (struct variable*)vm_exit_message(context, "bad math float operator");
+    }
+    return variable_new_float(context, f);
+}
+
+static bool is_num(enum VarType vt) {
+    return vt == VAR_INT || vt == VAR_FLT;
+}
+
+static struct variable *binary_op_str(struct Context *context,
+                                      enum Opcode op,
+                                      const struct variable *u,
+                                      const struct variable *v)
+{
+    null_check(context);
+    struct variable *w = NULL;
+    struct byte_array *ustr = variable_value(context, u);
+    struct byte_array *vstr = variable_value(context, v);
+
+    switch (op) {
+        case VM_ADD:    w = variable_new_str(context, byte_array_concatenate(2, vstr, ustr));    break;
+        case VM_EQU:    w = variable_new_int(context, byte_array_equals(ustr, vstr));            break;
+        default:
+            return (struct variable*)vm_exit_message(context, "unknown string operation");
+    }
+    return w;
+}
+
+static bool variable_compare(struct Context *context,
+                             const struct variable *u,
+                             const struct variable *v)
+{
+    null_check(context);
+    if (!u != !v)
+        return false;
+    enum VarType ut = (enum VarType)u->type;
+    enum VarType vt = (enum VarType)v->type;
+
+    if (ut != vt)
+        return false;
+
+    switch (ut) {
+        case VAR_LST:
+            if (u->list->length != v->list->length)
+                return false;
+            for (int i=0; i<u->list->length; i++) {
+                struct variable *ui = (struct variable*)array_get(u->list, i);
+                struct variable *vi = (struct variable*)array_get(v->list, i);
+                if (!variable_compare(context, ui, vi))
+                    return false;
+            }
+            // for list, check the map too
+        case VAR_MAP: {
+            struct array *keys = map_keys(u->map);
+            for (int i=0; i<keys->length; i++) {
+                struct byte_array *key = (struct byte_array*)array_get(keys, i);
+                struct variable *uvalue = (struct variable*)map_get(u->map, key);
+                struct variable *vvalue = (struct variable*)map_get(v->map, key);
+                if (!variable_compare(context, uvalue, vvalue))
+                    return false;
+            }
+            return true; }
+        case VAR_INT:
+            return u->integer == v->integer;
+        case VAR_FLT:
+            return u->floater == v->floater;
+        case VAR_STR:
+            return byte_array_equals(u->str, v->str);
+        default:
+            return (bool)vm_exit_message(context, "bad comparison");
+    }
+}
+
+static struct variable *binary_op_lst(struct Context *context,
+                                      enum Opcode op,
+                                      const struct variable *u,
+                                      const struct variable *v)
+{
+    null_check(context);
+    vm_assert(context, u->type==VAR_LST && v->type==VAR_LST, "list op with non-lists");
+    struct variable *w = NULL;
+
+    switch (op) {
+        case VM_ADD:
+            w = variable_copy(context, v);
+            for (int i=0; i<u->list->length; i++)
+                array_add(w->list, array_get(u->list, i));
+            map_update(w->map, u->map);
+            break;
+        default:
+            return (struct variable*)vm_exit_message(context, "unknown string operation");
+    }
+
+    return w;
+}
+
+static void binary_op(struct Context *context, enum Opcode op)
+{
+    null_check(context);
+    if (!context->runtime)
+        VM_DEBUGPRINT("%s\n", NUM_TO_STRING(opcodes, op));
+
+    const struct variable *u = variable_pop(context);
+    const struct variable *v = variable_pop(context);
+    struct variable *w;
+
+    if (op == VM_EQU) {
+        bool same = variable_compare(context, u, v);
+        w = variable_new_int(context, same);
+    } else {
+
+        enum VarType ut = (enum VarType)u->type;
+        enum VarType vt = (enum VarType)v->type;
+        bool floater  = (ut == VAR_FLT && is_num(vt)) || (vt == VAR_FLT && is_num(ut));
+
+        if (vt == VAR_STR || ut == VAR_STR)         w = binary_op_str(context, op, u, v);
+        else if (floater)                           w = binary_op_float(context, op, u, v);
+        else if (ut == VAR_INT && vt == VAR_INT)    w = binary_op_int(context, op, v, u);
+        else if (vt == VAR_LST)                     w = binary_op_lst(context, op, u, v);
+        else
+            vm_exit_message(context, "unknown binary op");
+    }
+
+    variable_push(context, w);
+
+    DEBUGPRINT("%s(%s,%s) = %s\n",
+               NUM_TO_STRING(opcodes, op),
+               variable_value_str(context, v),
+               variable_value_str(context, u),
+               variable_value_str(context, w));
+}
+
+static void unary_op(struct Context *context, enum Opcode op)
+{
+    null_check(context);
+    if (!context->runtime)
+        VM_DEBUGPRINT("%s\n", NUM_TO_STRING(opcodes, op));
+
+    struct variable *v = (struct variable*)variable_pop(context);
+    struct variable *result = NULL;
+
+    switch (v->type) {
+        case VAR_NIL:
+        {
+            switch (op) {
+                case VM_NEG:    result = variable_new_nil(context);            break;
+                case VM_NOT:    result = variable_new_bool(context, true);       break;
+                default:        vm_exit_message(context, "bad math operator");   break;
+            }
+        } break;
+        case VAR_INT: {
+            int32_t n = v->integer;
+            switch (op) {
+                case VM_NEG:    result = variable_new_int(context, -n);          break;
+                case VM_NOT:    result = variable_new_bool(context, !n);         break;
+                case VM_INV:    result = variable_new_int(context, ~n);          break;
+                default:        vm_exit_message(context, "bad math operator");   break;
+            }
+        } break;
+        default:
+            vm_exit_message(context, "bad math type");
+            break;
+    }
+
+    variable_push(context, result);
+
+    DEBUGPRINT("%s(%s) = %s\n",
+               NUM_TO_STRING(opcodes, op),
+               variable_value_str(context, v),
+               variable_value_str(context, result));
+}
+
+// FOR who IN what WHERE where DO how
+static void iterate(struct Context *context, 
+                    enum Opcode op,
+                    struct program_state *state,
+                    struct byte_array *program)
+{
+    null_check(context);
+    struct byte_array *who = serial_decode_string(program);
+    struct byte_array *where = serial_decode_string(program);
+    struct byte_array *how = serial_decode_string(program);
+
+#ifdef DEBUG
+    DEBUGPRINT("%s %s\n",
+               NUM_TO_STRING(opcodes, op),
+               byte_array_to_string(who));
+    if (!context->runtime) {
+        if (where) {
+            DEBUGPRINT("%s\tWHERE\n", indentation(context));
+            display_code(context, where);
+        }
+        DEBUGPRINT("%s\tDO\n", indentation(context));
+        display_code(context, how);
+        return;
+    }
+#endif
+
+    bool comprehending = (op == VM_COM);
+    struct variable *result = comprehending ? variable_new_list(context, NULL) : NULL;
+
+    struct variable *what = variable_pop(context);
+    for (int i=0; i<what->list->length; i++) {
+
+        struct variable *that = (struct variable*)array_get(what->list, i);
+        set_named_variable(context, state, who, that);
+
+        byte_array_reset(where);
+        byte_array_reset(how);
+        run(context, where, true);
+        if (test_operand(context)) {
+
+            run(context, how, true);
+
+            if (comprehending) {
+                struct variable *item = (struct variable*)stack_pop(context->operand_stack);
+                array_add(result->list, item);
+            }
+        }
+    }
+
+    if (comprehending)
+        stack_push(context->operand_stack, result);
+}
+
+static inline void vm_trycatch(struct Context *context, struct byte_array *program)
+{
+    struct byte_array *trial = serial_decode_string(program);
+    DEBUGPRINT("TRY %d\n", trial->length);
+    display_code(context, trial);
+    struct byte_array *name = serial_decode_string(program);
+    struct byte_array *catcher = serial_decode_string(program);
+    DEBUGPRINT("%sCATCH %s %d\n", indentation(context), byte_array_to_string(name), catcher->length);
+    display_code(context, catcher);
+    if (!context->runtime)
+        return;
+
+    run(context, trial, true);
+    if (context->vm_exception) {
+        set_named_variable(context, NULL, name, context->vm_exception);
+        context->vm_exception = NULL;
+        run(context, catcher, true);
+    }
+}
+
+struct variable *run(struct Context *context, struct byte_array *program, bool in_context)
+{
+    null_check(context);
+    struct program_state *state = NULL;
+    program->current = program->data;
+    if (context->runtime) {
+        if (in_context)
+            state = (struct program_state*)stack_peek(context->program_stack, 0);
+        else
+            state = program_state_new(context);
+    }
+    //DEBUGPRINT("run %d %d %p\n", runtime, context, state);
+    //DEBUGPRINT("\t%p < %p + %d? %s\n", program->current, program->data, program->length, program->current < program->data + program->length ? "yes":"no");
+
+    while (program->current < program->data + program->length) {
+        enum Opcode inst = (enum Opcode)*program->current;
+#ifdef DEBUG
+        display_program_counter(context, program);
+#endif
+        program->current++; // increment past the instruction
+
+        if (inst == VM_RET) {
+            src(context, inst, program);
+            break;
+        } else if (inst == VM_TRO) {
+            DEBUGPRINT("THROW\n");
+            if (context->runtime) {
+                context->vm_exception = (struct variable*)stack_pop(context->operand_stack);
+                break;
+            } else
+                continue;
+        }
+
+        int32_t pc_offset = 0;
+
+        switch (inst) {
+            case VM_MUL:
+            case VM_DIV:
+            case VM_ADD:
+            case VM_SUB:
+            case VM_AND:
+            case VM_EQU:
+            case VM_NEQ:
+            case VM_GTN:
+            case VM_LTN:
+            case VM_BND:
+            case VM_BOR:
+            case VM_MOD:
+            case VM_XOR:
+            case VM_INV:
+            case VM_RSF:
+            case VM_LSF:
+            case VM_OR:     binary_op(context, inst);               break;
+            case VM_NEG:
+            case VM_NOT:    unary_op(context, inst);                break;
+            case VM_SRC:    src(context, inst, program);            break;
+            case VM_DST:    dst(context);                           break;
+            case VM_SET:    set(context, state, program);           break;
+            case VM_JMP:    pc_offset = jump(context, program);     break;
+            case VM_IFF:    pc_offset = iff(context, program);      break;
+            case VM_CAL:    func_call(context);                     break;
+            case VM_LST:    push_list(context, program);            break;
+            case VM_MAP:    push_map(context, program);             break;
+            case VM_GET:    list_get(context);                      break;
+            case VM_PUT:    list_put(context);                      break;
+            case VM_NIL:    push_nil(context);                      break;
+            case VM_INT:    push_int(context, program);             break;
+            case VM_FLT:    push_float(context, program);           break;
+            case VM_BOOL:   push_bool(context, program);            break;
+            case VM_STR:    push_str(context, program);             break;
+            case VM_VAR:    push_var(context, program);             break;
+            case VM_FNC:    push_fnc(context, program);             break;
+            case VM_MET:    method(context, program);               break;
+            case VM_COM:
+            case VM_ITR:    iterate(context, inst, state, program); break;
+            case VM_TRY:    vm_trycatch(context, program);          break;
+            default:
+                return (struct variable*)vm_exit_message(context, ERROR_OPCODE);
+        }
+        program->current += pc_offset;
+    }
+
+    //DEBUGPRINT("run done %d %d %p\n", runtime, context, state);
+    if (!context->runtime)
+        return NULL;
+    if (!in_context)
+        stack_pop(context->program_stack);
+    return (struct variable*)stack_peek(context->operand_stack, 0);
+}
+
+struct variable *execute(struct byte_array *program,
+                         bool in_context,
+                         bridge *callback_to_c)
+{
+    null_check(program);
+    DEBUGPRINT("execute:\n");
+    struct Context *context = vm_init();
+    context->callback2c = callback_to_c;
+    vm_assert(context, program!=0 && program->data!=0, ERROR_NULL);
+    byte_array_reset(program);
+    struct byte_array* code = serial_decode_string(program);
+
+#ifdef DEBUG
+    context->indent = 1;
+#endif
+
+    struct variable *v;
+    if (!setjmp(trying))
+        v = run(context, code, in_context);
+    else
+        v = context->error;
+
+    return v;
+}
diff -r 000000000000 -r 1a89e28dea91 vm.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/vm.h	Wed May 30 21:13:01 2012 +0000
@@ -0,0 +1,88 @@
+#ifndef VM_H
+#define VM_H
+
+
+#include <stdint.h>
+#include <inttypes.h>
+#include "struct.h"
+#include "util.h"
+#include "variable.h"
+
+#define ERROR_NULL  "null pointer"
+#define ERROR_INDEX "index out of bounds"
+
+struct Context {
+    struct program_state *vm_state;
+    struct stack *program_stack;
+    struct stack *operand_stack;
+    struct stack *rhs;
+    struct variable *vm_exception;
+    bridge *callback2c;
+    bool runtime;
+    uint32_t num_vars;
+    struct variable* error;
+    uint8_t indent;
+};
+
+enum Opcode {
+    VM_NIL,    //    push nil
+    VM_INT,    //    push an integer
+    VM_FLT,    //    push a float
+    VM_BOOL,//    push a boolean
+    VM_STR,    //    push a string
+    VM_VAR,    //    push a variable
+    VM_FNC,    //    push a function
+    VM_DST,    //    done with assignment
+    VM_SET, //  set a variable
+    VM_SRC,    //    push a set of values
+    VM_LST,    //    push a list
+    VM_MAP,    //    push a map
+    VM_GET,    //    get an item from a list or map
+    VM_PUT,    //    put an item in a list or map
+    VM_ADD,    //    add two values
+    VM_SUB,    //    subtract two values
+    VM_MUL,    //    multiply two values
+    VM_DIV,    //    divide two values
+    VM_MOD,    //    modulo
+    VM_BND,    //    bitwise and
+    VM_BOR,    //    bitwise or
+    VM_INV,    //    bitwise inverse
+    VM_XOR,    //    xor
+    VM_LSF,    //    left shift
+    VM_RSF,    //    right shift
+    VM_NEG,    //    arithmetic negate a value
+    VM_NOT,    //    boolean negate a value
+    VM_EQU,    //    compare
+    VM_NEQ,    //    diff
+    VM_GTN,    //    greater than
+    VM_LTN,    //    less than
+    VM_AND,    //    logical and
+    VM_OR,    //    logical or
+    VM_IFF,    //    if then
+    VM_JMP,    //    jump the program counter
+    VM_CAL,    //    call a function
+    VM_MET,    //    call an object method
+    VM_RET,    //    return from a function,
+    VM_ITR,    //    iteration loop
+    VM_COM,    //    comprehension
+    VM_TRY,    //    try.catch
+    VM_TRO, //    throw
+};
+
+#define ERROR_OPCODE "unknown opcode"
+
+#ifdef DEBUG
+void display_program(struct byte_array* program);
+#endif
+struct Context *vm_init();
+struct variable *execute(struct byte_array *program,
+                         bool in_context,
+                         bridge *callback_to_c);
+void garbage_collect(struct Context *context);
+
+void vm_call(struct Context *context);
+void *vm_exit_message(struct Context *context, const char *format, ...);
+void vm_null_check(struct Context *context, const void* p);
+void vm_assert(struct Context *context, bool assertion, const char *format, ...);
+
+#endif // VM_H