Revision 0:fc1335b7b54f, committed 2019-12-23

Comitter:

manitou

Date:

Mon Dec 23 18:56:56 2019 +0000

Commit message:

stochastic simulation

Changed in this revision

diff -r 000000000000 -r fc1335b7b54f Ant.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Ant.cpp	Mon Dec 23 18:56:56 2019 +0000
@@ -0,0 +1,89 @@
+//
+//  Ant.cpp
+//  INHERITANCE_AND_POLYMORPHISM
+//
+//  Created by Kristjan Thorsteinsson on 01/04/14.
+//  Copyright (c) 2014 Kristjan Thorsteinsson. All rights reserved.
+//
+#include <cstdlib>
+
+//#include <iostream>
+#include "Ant.h"
+#include "Organism.h"
+#include "World.h"
+using namespace std;
+
+Ant::Ant(World* aWorld, int xcoord, int ycoord) : Organism(aWorld, xcoord, ycoord)
+{
+
+}
+
+void Ant::move()
+{
+  breedTicks++;
+  Move mover = world->randomMove();
+  switch (mover) {
+    case UP:
+      if (world->getAt(x, y + 1) == NULL && in_range(x, y + 1))
+      {
+        movesTo(x, y + 1);
+      }
+      break;
+    case DOWN:
+      if (world->getAt(x, y - 1) == NULL && in_range(x, y - 1))
+      {
+        movesTo(x, y - 1);
+      }
+      break;
+    case LEFT:
+      if (world->getAt(x - 1, y) == NULL && in_range(x - 1, y))
+      {
+        movesTo(x - 1, y);
+      }
+      break;
+    case RIGHT:
+      if (world->getAt(x + 1, y) == NULL && in_range(x + 1, y))
+      {
+        movesTo(x + 1, y);
+      }
+      break;
+    default:
+      break;
+  }
+}
+
+void Ant::breed()
+{
+  if (breedTicks >= BREED_ANTS)
+  {
+    breedAtAdjacentCell();
+  }
+}
+
+
+void Ant::generateOffspring(int whereX, int whereY)
+{
+  new Ant(this->world, whereX, whereY);
+  breedTicks = 0;
+}
+
+
+OrganismType Ant::getType() const
+{
+  return ANT;
+}
+
+char Ant::representation() const
+{
+  return 'o';
+}
+
+int Ant::size() const
+{
+  return 10;
+}
+
+bool Ant::in_range(int xx, int yy)
+{
+  return (xx >= 0) && (xx < ROWS) && (yy >= 0) && (yy < COLS);
+}

diff -r 000000000000 -r fc1335b7b54f Ant.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Ant.h	Mon Dec 23 18:56:56 2019 +0000
@@ -0,0 +1,44 @@
+//
+//  Ant.h
+//  INHERITANCE_AND_POLYMORPHISM
+//
+//  Created by Kristjan Thorsteinsson on 01/04/14.
+//  Copyright (c) 2014 Kristjan Thorsteinsson. All rights reserved.
+//
+
+#ifndef INHERITANCE_AND_POLYMORPHISM_Ant
+#define INHERITANCE_AND_POLYMORPHISM_Ant
+
+//#include <iostream>
+#include "Organism.h"
+#include "World.h"
+#include "Counter.h"
+
+class Ant : public Organism, public counter<Ant>
+{
+public:
+    
+    Ant(World* aWorld, int xcoord, int ycoord);
+    // In the given world moves this organism.
+    void move();
+    
+    // Makes this organism breed.
+    void breed();
+    
+    // Returns the type of this organism.
+    OrganismType getType() const;
+    
+    // The character representation of this organism.
+    char representation() const;
+    
+    // The size of this organism.
+    int size() const;
+    
+    bool in_range(int xx, int yy);
+    
+private:
+    
+    void generateOffspring(int whereX, int whereY);
+};
+
+#endif /* defined(__INHERITANCE_AND_POLYMORPHISM__Ant__) */

diff -r 000000000000 -r fc1335b7b54f Bug.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Bug.cpp	Mon Dec 23 18:56:56 2019 +0000
@@ -0,0 +1,207 @@
+//
+//  Bug.cpp
+//  INHERITANCE_AND_POLYMORPHISM
+//
+//  Created by Kristjan Thorsteinsson on 01/04/14.
+//  Copyright (c) 2014 Kristjan Thorsteinsson. All rights reserved.
+//
+
+#include "Bug.h"
+#include "Organism.h"
+using namespace std;
+
+Bug::Bug(World* aWorld, int xcoord, int ycoord) : Organism(aWorld, xcoord, ycoord)
+{
+  starveTicks = 0;
+}
+
+
+void Bug::move()
+{
+  breedTicks++;
+  starveTicks++;
+
+#if 1
+  // find an edible nabor
+  for (int i = 0; i < NABORS; i++) {
+    switch (nabors[i]) {
+      case 0:
+        if (world->getAt(x, y + 1) != NULL)
+        {
+          if (world->getAt(x, y + 1)->getType() == ANT)
+          {
+            starveTicks = 0;
+            delete world->getAt(x, y + 1);
+            movesTo(x, y + 1);
+            return;
+          }
+        }
+        break;
+
+      case 1:
+        if (world->getAt(x, y - 1) != NULL)
+        {
+          if (world->getAt(x, y - 1)->getType() == ANT)
+          {
+            starveTicks = 0;
+            delete world->getAt(x, y - 1);
+            movesTo(x, y - 1);
+            return;
+          }
+        }
+        break;
+
+      case 2:
+        if (world->getAt(x - 1, y) != NULL)
+        {
+          if (world->getAt(x - 1, y)->getType() == ANT)
+          {
+            starveTicks = 0;
+            delete world->getAt(x - 1, y);
+            movesTo(x - 1, y);
+            return;
+          }
+        }
+        break;
+
+      case 3:
+        if (world->getAt(x + 1, y) != NULL)
+        {
+          if (world->getAt(x + 1, y)->getType() == ANT)
+          {
+            starveTicks = 0;
+            delete world->getAt(x + 1, y);
+            movesTo(x + 1, y);
+            return;
+          }
+        }
+        break;
+
+      default:
+        break;
+    }
+  }   // for nabors
+#else
+
+  if (world->getAt(x, y + 1) != NULL)
+  {
+    if (world->getAt(x, y + 1)->getType() == ANT)
+    {
+      starveTicks = 0;
+      delete world->getAt(x, y + 1);
+      movesTo(x, y + 1);
+      return;
+    }
+  }
+
+  if (world->getAt(x, y - 1) != NULL)
+  {
+    if (world->getAt(x, y - 1)->getType() == ANT)
+    {
+      starveTicks = 0;
+      delete world->getAt(x, y - 1);
+      movesTo(x, y - 1);
+      return;
+    }
+  }
+
+  if (world->getAt(x - 1, y) != NULL)
+  {
+    if (world->getAt(x - 1, y)->getType() == ANT)
+    {
+      starveTicks = 0;
+      delete world->getAt(x - 1, y);
+      movesTo(x - 1, y);
+      return;
+    }
+  }
+  if (world->getAt(x + 1, y) != NULL)
+  {
+    if (world->getAt(x + 1, y)->getType() == ANT)
+    {
+      starveTicks = 0;
+      delete world->getAt(x + 1, y);
+      movesTo(x + 1, y);
+      return;
+    }
+  }
+#endif
+
+  Move mover = world->randomMove();
+  switch (mover) {
+    case UP:
+      if (world->getAt(x, y + 1) == NULL && in_range(x, y + 1))
+      {
+        movesTo(x, y + 1);
+      }
+      break;
+    case DOWN:
+      if (world->getAt(x, y - 1) == NULL && in_range(x, y - 1))
+      {
+        movesTo(x, y - 1);
+      }
+      break;
+    case LEFT:
+      if (world->getAt(x - 1, y) == NULL && in_range(x - 1, y))
+      {
+        movesTo(x - 1, y);
+      }
+      break;
+    case RIGHT:
+      if (world->getAt(x + 1, y) == NULL && in_range(x + 1, y))
+      {
+        movesTo(x + 1, y);
+      }
+      break;
+    default:
+      break;
+  }
+}
+
+void Bug::generateOffspring(int whereX, int whereY)
+{
+  new Bug(this->world, whereX, whereY);
+  breedTicks = 0;
+}
+
+void Bug::breed()
+{
+  if (breedTicks >= BREED_BUGS)
+  {
+    breedAtAdjacentCell();
+  }
+
+}
+
+bool Bug::isDead() const
+{
+  if (starveTicks >= STARVE_BUGS)
+  {
+    return true;
+  }
+  else
+  {
+    return false;
+  }
+}
+
+OrganismType Bug::getType() const
+{
+  return BUG;
+}
+
+
+char Bug::representation()const
+{
+  return 'X';
+}
+
+int Bug::size() const
+{
+  return 30;
+}
+
+bool Bug::in_range(int xx, int yy)
+{
+  return (xx >= 0) && (xx < ROWS) && (yy >= 0) && (yy < COLS);
+}

diff -r 000000000000 -r fc1335b7b54f Bug.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Bug.h	Mon Dec 23 18:56:56 2019 +0000
@@ -0,0 +1,48 @@
+//
+//  Bug.h
+//  INHERITANCE_AND_POLYMORPHISM
+//
+//  Created by Kristjan Thorsteinsson on 01/04/14.
+//  Copyright (c) 2014 Kristjan Thorsteinsson. All rights reserved.
+//
+
+#ifndef INHERITANCE_AND_POLYMORPHISM_Bug
+#define INHERITANCE_AND_POLYMORPHISM_Bug
+
+//#include <iostream>
+
+#include "World.h"
+#include "Organism.h"
+#include "Counter.h"
+
+class Bug : public Organism, public counter<Bug>
+{
+public:
+    
+    Bug(World* aWorld, int xcoord, int ycoord);
+    // In the given world moves this organism.
+    void move();
+    
+    // Makes this organism breed.
+    void breed();
+    
+    // Returns the type of this organism.
+    OrganismType getType() const;
+    
+    // The character representation of this organism.
+    char representation() const;
+    
+    // The size of this organism.
+    int size() const;
+    // Returns true if organism is dead, false otherwise.
+    bool isDead() const;
+    
+    bool in_range(int xx, int yy);
+    
+private:
+    
+    void generateOffspring(int whereX, int whereY);
+    int starveTicks;
+};
+
+#endif /* defined(__INHERITANCE_AND_POLYMORPHISM__Bug__) */

diff -r 000000000000 -r fc1335b7b54f Counter.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Counter.h	Mon Dec 23 18:56:56 2019 +0000
@@ -0,0 +1,21 @@
+#ifndef MYCOUNTER
+#define MYCOUNTER
+template <typename T>
+struct counter
+{
+    counter()
+    {
+        objects_created++;
+        objects_alive++;
+    }
+
+    virtual ~counter()
+    {
+        --objects_alive;
+    }
+    static int objects_created;
+    static int objects_alive;
+};
+template <typename T> int counter<T>::objects_created( 0 );
+template <typename T> int counter<T>::objects_alive( 0 );
+#endif

diff -r 000000000000 -r fc1335b7b54f Organism.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Organism.cpp	Mon Dec 23 18:56:56 2019 +0000
@@ -0,0 +1,104 @@
+//#include <iostream>
+#include "Organism.h"
+#include "World.h"
+
+// Create an organism at the given coordinates in the given world.
+Organism::Organism(World* aWorld, int xcoord, int ycoord) {
+  world = aWorld;
+  x = xcoord;
+  y = ycoord;
+  breedTicks = 0;
+  moved = false;
+  world->setAt(x, y, this);
+}
+
+// flags the organism as moved or not
+void Organism::setMoved(bool hasMoved) {
+  moved = hasMoved;
+}
+
+// has the organism moved or not?
+bool Organism::hasMoved() const {
+  return moved;
+}
+
+// moves the organism from coordinates (x,y) to (xNew,yNew)
+void Organism::movesTo(int xNew, int yNew) {
+
+  world->setAt(xNew, yNew, world->getAt(x, y));
+
+  world->setAt(x, y, NULL);
+
+  x = xNew;
+  y = yNew;
+
+  world->getAt(x, y)->setMoved(true);
+}
+
+// Breeds an organism at an adjacent cell. This method calls the
+// generateOffspring() method.
+void Organism::breedAtAdjacentCell()  {
+#if 1
+  // find empty nabor for breeding
+  for (int i = 0; i < NABORS; i++) {
+    switch (nabors[i]) {
+      case 0:
+        if ((world->getAt(x, y + 1) == NULL) && in_range(x, y + 1))
+        {
+          generateOffspring(x, y + 1);
+          return;
+        }
+        break;
+      case 1:
+        if ((world->getAt(x, y - 1) == NULL) && in_range(x, y - 1))
+        {
+          generateOffspring(x, y - 1);
+          return;
+        }
+        break;
+      case 2:
+        if ((world->getAt(x - 1, y) == NULL)  && in_range(x - 1, y))
+        {
+          generateOffspring(x - 1, y);
+          return;
+        }
+      case 3:
+        if ((world->getAt(x + 1, y) == NULL)  && in_range(x + 1, y))
+        {
+          generateOffspring(x + 1, y);
+          return;
+        }
+        break;
+      default:
+        break;
+    }
+  }  // nabor for
+#else
+  if ((world->getAt(x, y + 1) == NULL) && in_range(x, y + 1))
+  {
+    generateOffspring(x, y + 1);
+  }
+  else if ((world->getAt(x, y - 1) == NULL) && in_range(x, y - 1))
+  {
+    generateOffspring(x, y - 1);
+  }
+  else if ((world->getAt(x - 1, y) == NULL)  && in_range(x - 1, y))
+  {
+    generateOffspring(x - 1, y);
+  }
+  else if ((world->getAt(x + 1, y) == NULL)  && in_range(x + 1, y))
+  {
+    generateOffspring(x + 1, y);
+  }
+#endif
+}
+
+
+bool Organism::in_range(int xx, int yy)
+{
+  return (xx >= 0) && (xx < ROWS) && (yy >= 0) && (yy < COLS);
+}
+// Returns true if organism is dead, false otherwise.
+bool Organism::isDead() const {
+  return false;
+}

diff -r 000000000000 -r fc1335b7b54f Organism.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Organism.h	Mon Dec 23 18:56:56 2019 +0000
@@ -0,0 +1,70 @@
+#ifndef ORGANISM_H
+#define ORGANISM_H
+
+enum OrganismType {ANT, BUG};
+
+// forward declaration
+class World;
+
+class Organism {
+    public:
+        // Create an organism at the given coordinates.
+        Organism(World* aWorld, int xcoord, int ycoord);
+        virtual ~Organism() { }
+
+        // In the given world moves this organism.
+        virtual void move() = 0;
+
+        // Makes this organism breed.
+        virtual void breed() = 0;
+
+        // Returns the type of this organism.
+        virtual OrganismType getType() const = 0;
+
+        // Flags this organism as moved or not.
+        void setMoved(bool hasMoved);
+
+        // The character representation of this organism.
+        virtual char representation() const = 0;
+
+        // The size of this organism.
+        virtual int size() const = 0;
+
+        // Has this organism moved in this time slot or not?
+        bool hasMoved() const;
+
+        // Returns true if organism is dead, false otherwise.
+        virtual bool isDead() const;
+    
+        bool in_range(int xx, int yy);
+    
+    protected:
+        // Generates an offspring at the given position.
+        virtual void generateOffspring(int whereX, int whereY) = 0;
+
+        // Moves this organism from coordinates (x,y) to (xNew,yNew).
+        void movesTo(int xNew, int yNew);
+
+        // Breeds a new organism at an adjacent cell. Tries to produce one new
+        // organism in UP, DOWN, LEFT, or RIGHT cell (in that order).  Makes
+        // sure not to breed off the grid.
+        void breedAtAdjacentCell();
+
+        // This organism's x position in the world.
+        int x;
+
+        // This organism's y position in the world.
+        int y;
+
+        // Has moved this turn?
+        bool moved;
+
+        // Number of ticks since breeding.
+        int breedTicks;
+
+        // A pointer to the world in which this organism lives.
+        World* world;
+    private:
+};
+
+#endif // ORGANISM_H

diff -r 000000000000 -r fc1335b7b54f World.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/World.cpp	Mon Dec 23 18:56:56 2019 +0000
@@ -0,0 +1,223 @@
+#include "mbed.h"
+
+#include "World.h"
+#include "Ant.h"
+#include "Bug.h"
+
+extern Timer tmr;
+#define micros tmr.read_us
+
+#define CELL 9
+
+int nabors[NABORS];
+
+
+///////////////////
+// Public functions
+///////////////////
+
+// Default constructor: creates and initializes the world
+// the seed is used for seeding the random behaviour.
+World::World(unsigned int seed) {
+  srand(seed);             // seed the random generator
+  steps = 0;
+  step_us = 0;
+  for(int i=0; i < NABORS; i++) nabors[i] =i;
+  // Create an empty world
+  for (int i = 0; i < ROWS; i++) {
+    for (int j = 0; j < COLS; j++) {
+      grid[i][j] = NULL;
+    }
+  }
+  // creates the ants = 3
+  createOrganisms(ANT, INITIAL_ANTS);
+  // creates the bugs = 8
+  createOrganisms(BUG, INITIAL_BUGS);
+}
+
+// Deallocate memory allocated to organisms in this world.
+World::~World() {
+  for (int i = 0; i < ROWS; i++) {
+    for (int j = 0; j < COLS; j++) {
+      if (grid[i][j] != NULL) {
+        delete grid[i][j];
+      }
+    }
+  }
+}
+
+// Return the organism at the given coordinates
+// If the coordinates are not valid, returns NULL
+Organism* World::getAt(int x, int y) const {
+  if ((x >= 0) && (x < ROWS) && (y >= 0) && (y < COLS)) {
+    return grid[x][y];
+  } else {
+    return NULL;
+  }
+}
+
+// Sets the entry at x,y to the value passed in.
+void World::setAt(int x, int y, Organism* org) {
+  if ((x >= 0) && (x < ROWS) && (y >= 0) && (y < COLS)) {
+    grid[x][y] = org;
+  }
+}
+
+// Displays the world in ASCII.
+void World::print() const {
+
+  printf("\n");
+  for (int i = 0; i < ROWS; i++) {
+    for (int j = 0; j < COLS; j++) {
+      if (grid[i][j] == NULL) {
+        printf( ".");
+      } else {
+        printf("%c", grid[i][j]->representation());
+      }
+    }
+    printf("\n");
+  }
+  // cout << "Ants: " << numAnts << " Bugs: " << numBugs << endl;
+  printf("Ants: %d  Bugs: %d steps %d  %d us\n",counter<Ant>::objects_alive,counter<Bug>::objects_alive,steps,step_us);
+  #if 0
+  Serial.print("Ants: "); Serial.print(counter<Ant>::objects_alive);
+  Serial.print("  Bugs: "); Serial.print(counter<Bug>::objects_alive);
+  Serial.print("  steps: "); Serial.print(steps);
+  Serial.print(" "); Serial.print(step_us); Serial.println(" us");
+  #endif
+}
+
+// for serialplotter
+void World::plot() const {
+  //Serial.print("Ants: "); Serial.print(counter<Ant>::objects_alive);
+  //Serial.print("  Bugs: "); Serial.println(counter<Bug>::objects_alive);
+  //Serial.println(step_us);
+}
+
+
+
+void World::simulateOneStep() {
+  // The main routine that simulates one turn in the world:
+  // 1. move bugs
+  // 2. move ants
+  // 3. make bugs starve (which happends under a certain condition)
+  // 4. make the organisms breed (again which happens under a certain
+  // condition).
+
+  steps++;
+  step_us = micros();
+    // shuffle nabors
+  for (int i=0; i< NABORS; i++) {
+    int n = rand() % NABORS;
+    int tmp = nabors[n];
+    nabors[n] = nabors[i];
+    nabors[i] = tmp;
+  }
+  // Reset all organisms to not moved
+  resetOrganisms();
+
+  // Move the bugs
+  moveOrganism(BUG);
+
+  // Move the ants
+  moveOrganism(ANT);
+
+  // Make the bugs starve
+  cleanup();
+
+  //Make them breed
+  breedOrganisms();
+  step_us = micros() - step_us;
+}
+
+Position World::randomPosition() const {    // returns a random number in the range 0 to MAX-1
+  Position p;
+  p.x = rand() % ROWS;
+  p.y = rand() % COLS;
+  return p;
+}
+
+
+Move World::randomMove() const {
+  return static_cast<Move>(rand() % 4);
+}
+
+////////////////////
+// Private functions
+////////////////////
+
+void World::createOrganisms(OrganismType orgType, int count) {
+  int orgCount = 0;
+  while (orgCount < count) {
+    Position p = randomPosition();
+
+    // Only put ant in empty spot
+    if (grid[p.x][p.y] == NULL) {
+      orgCount++;
+      if (orgType == ANT) {
+        new Ant(this, p.x, p.y);   // Create an Ant and put it into the world
+      }
+      else if (orgType == BUG) {
+        new Bug(this, p.x, p.y);   // Create a Bug and put it into the world
+      }
+    }
+  }
+}
+
+// Reset all organisms to not moved
+void World::resetOrganisms() {
+  for (int i = 0; i < ROWS; i++)
+  {
+    for (int j = 0; j < COLS; j++)
+    {
+      if (grid[i][j] != NULL)
+      {
+        grid[i][j]->setMoved(false);
+      }
+    }
+  }
+}
+
+// Move all organisms of type aType
+void World::moveOrganism(OrganismType aType) {
+  for (int i = 0; i < ROWS; i++)
+  {
+    for (int j = 0; j < COLS; j++)
+    {
+      if (grid[i][j] != NULL)
+      {
+        if (grid[i][j]->getType() == aType && !(grid[i][j]->hasMoved()))
+        {
+          grid[i][j]->move();
+        }
+      }
+    }
+  }
+}
+
+// Remove all dead organisms from this world.
+void World::cleanup() {
+  for (int i = 0; i < ROWS; i++) {
+    for (int j = 0; j < COLS; j++) {
+      // Kill off any organisms that haven't eaten recently
+      if ((grid[i][j] != NULL) && grid[i][j]->isDead()) {
+        delete grid[i][j];
+        grid[i][j] = NULL;
+      }
+    }
+  }
+}
+
+// Make the organisms breed
+void World::breedOrganisms() {
+  for (int i = 0; i < ROWS; i++)
+  {
+    for (int j = 0; j < COLS; j++)
+    {
+      if (grid[i][j] != NULL)
+      {
+        grid[i][j]->breed();
+      }
+    }
+  }
+}

diff -r 000000000000 -r fc1335b7b54f World.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/World.h	Mon Dec 23 18:56:56 2019 +0000
@@ -0,0 +1,114 @@
+#ifndef WORLD_H
+#define WORLD_H
+#include <stddef.h>
+
+#include "Organism.h"
+
+// The possible moves
+enum Move {UP = 0, DOWN, LEFT, RIGHT};
+
+// The size of this world
+const int ROWS = 24, COLS = 32;
+
+// Number of initial ants
+const int INITIAL_ANTS = 50;
+
+// Number of initial bugs
+const int INITIAL_BUGS = 10;
+
+// Time steps between breeding of ants
+const int BREED_ANTS = 3;
+
+// Time steps between breeding of bugs
+const int BREED_BUGS = 8;
+
+// Time steps until bugs die if they have not eaten
+const int STARVE_BUGS = 3;
+
+const int NABORS = 4;
+extern  int nabors[];
+
+struct Position
+{
+    int x;
+    int y;
+};
+
+class World
+{
+    public:
+        // Constructor: creates and initializes this world. the seed is used for
+        // seeding the random behaviour.
+        World(unsigned int seed);
+
+        // Destructor.
+        ~World();
+
+        // Returns the organism at the given coordinates.
+        Organism* getAt(int x, int y) const;
+
+        // Sets the organism org at position (x,y).
+        void setAt(int x, int y, Organism* org);
+
+        // Displays this world.
+        void display() const;
+        void print() const;
+        void plot() const;
+
+        // Simulates one time step in this world.
+        void simulateOneStep();
+
+        // Returns a random position in the grid.
+        Position randomPosition() const;
+
+        // Returns a random move (UP, DOWN, LEFT or RIGHT).
+        Move randomMove() const;
+
+    private:
+        // The grid in which the organisms live. According the to image below,
+        // the correct iteration order through grid starts at the top left
+        // corner (i.e. grid[0][0]), loops through one column at a time and ends
+        // at the bottom right corner (i.e. grid[WORLDSIZE-1][WORLDSIZE-1]).
+        //
+        // grid[0, 0]          , grid[1, 0],      ...,      grid[WORLDSIZE-1, 0]
+        // grid[0, 1]          , grid[1, 1],      ...,      grid[WORLDSIZE-1, 1]
+        //    .                                                     .
+        //    .                                                     .
+        //    .                                                     .
+        // grid[0, WORLDSIZE-2], grid[1, WORLDSIZE-2], ..., grid[WORLDSIZE-1, WORLDSIZE-2]
+        // grid[0, WORLDSIZE-1], grid[1, WORLDSIZE-1], ..., grid[WORLDSIZE-1, WORLDSIZE-1]
+		//
+		// (See e.g. the destructor for correct iteration through the grid)
+        Organism* grid[ROWS][COLS];
+        unsigned long steps, step_us;
+
+        // Randomly create `count` many organisms of type `orgType`.  This
+        // method uses the parameterized constructor in Ant and Bug.
+        void createOrganisms(OrganismType orgType, int count);
+
+        // Reset all organisms to not moved. This is necessary because later we
+        // iterate through the grid starting from the top left moving to the
+        // bottom right looking for an organism to move. Say if an organism
+        // moves down, we don't want to move the organism again when we reach
+        // it.
+        void resetOrganisms();
+
+        // Make every organisms in this world of type aType move. Make sure to
+        // to iterate through grid in order as specified above and only move an
+        // organism if it hasn't moved already.
+        void moveOrganism(OrganismType aType);
+
+        // Remove all dead organism from this world. Iterates through the grid
+        // and uses the method Organism::isDead() to test if an organism is
+        // dead. For this assignment in this method, only starved bugs will be
+        // removed.
+        void cleanup();
+
+        // Make every organism in this world breed. Make sure to iterate
+        // through grid in order as specified above and to only breed organisms
+        // that have moved, since breeding places new organisms on the map we
+        // don't want to try and breed those.
+        void breedOrganisms();
+};
+
+#endif // WORLD_H

diff -r 000000000000 -r fc1335b7b54f main.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Mon Dec 23 18:56:56 2019 +0000
@@ -0,0 +1,37 @@
+// predator play stochastic simulation
+// https://github.com/Kristjan93/Ants-and-bugs
+
+#include "mbed.h"
+
+#include "World.h"
+Serial pc(USBTX, USBRX);
+Timer tmr;
+#define micros tmr.read_us
+
+main()
+{
+    tmr.start();
+
+
+  printf("hit a key to step\n");
+
+  World myWorld(0);   // seed  analogRead(0)
+
+  myWorld.print();
+ // myWorld.display();  // TFT display
+  while (1) {
+#if 1
+    if (pc.readable() ) {
+      pc.getc();
+      myWorld.simulateOneStep();
+      myWorld.print();
+   //   myWorld.display();  // TFT display
+    }
+#else
+    myWorld.simulateOneStep();
+    myWorld.plot();  // for serialplotter
+  //  myWorld.display();  // TFT display
+    wait(.3);
+#endif
+  }
+}

diff -r 000000000000 -r fc1335b7b54f mbed.bld
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbed.bld	Mon Dec 23 18:56:56 2019 +0000
@@ -0,0 +1,1 @@
+http://mbed.org/users/mbed_official/code/mbed/builds/f9eeca106725
\ No newline at end of file