Meta.h

00001 // This file is part of Eigen, a lightweight C++ template library
00002 // for linear algebra.
00003 //
00004 // Copyright (C) 2008-2009 Gael Guennebaud <gael.guennebaud@inria.fr>
00005 // Copyright (C) 2006-2008 Benoit Jacob <jacob.benoit.1@gmail.com>
00006 //
00007 // This Source Code Form is subject to the terms of the Mozilla
00008 // Public License v. 2.0. If a copy of the MPL was not distributed
00009 // with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
00010 
00011 #ifndef EIGEN_META_H
00012 #define EIGEN_META_H
00013 
00014 namespace Eigen {
00015 
00016 namespace internal {
00017 
00018 /** \internal
00019   * \file Meta.h
00020   * This file contains generic metaprogramming classes which are not specifically related to Eigen.
00021   * \note In case you wonder, yes we're aware that Boost already provides all these features,
00022   * we however don't want to add a dependency to Boost.
00023   */
00024 
00025 struct true_type {  enum { value = 1 }; };
00026 struct false_type { enum { value = 0 }; };
00027 
00028 template<bool Condition, typename Then, typename Else>
00029 struct conditional { typedef Then type; };
00030 
00031 template<typename Then, typename Else>
00032 struct conditional <false, Then, Else> { typedef Else type; };
00033 
00034 template<typename T, typename U> struct is_same { enum { value = 0 }; };
00035 template<typename T> struct is_same<T,T> { enum { value = 1 }; };
00036 
00037 template<typename T> struct remove_reference { typedef T type; };
00038 template<typename T> struct remove_reference<T&> { typedef T type; };
00039 
00040 template<typename T> struct remove_pointer { typedef T type; };
00041 template<typename T> struct remove_pointer<T*> { typedef T type; };
00042 template<typename T> struct remove_pointer<T*const> { typedef T type; };
00043 
00044 template <class T> struct remove_const { typedef T type; };
00045 template <class T> struct remove_const<const T> { typedef T type; };
00046 template <class T> struct remove_const<const T[]> { typedef T type[]; };
00047 template <class T, unsigned int Size> struct remove_const<const T[Size]> { typedef T type[Size]; };
00048 
00049 template<typename T> struct remove_all { typedef T type; };
00050 template<typename T> struct remove_all<const T>   { typedef typename remove_all<T>::type type; };
00051 template<typename T> struct remove_all<T const&>  { typedef typename remove_all<T>::type type; };
00052 template<typename T> struct remove_all<T&>        { typedef typename remove_all<T>::type type; };
00053 template<typename T> struct remove_all<T const*>  { typedef typename remove_all<T>::type type; };
00054 template<typename T> struct remove_all<T*>        { typedef typename remove_all<T>::type type; };
00055 
00056 template<typename T> struct is_arithmetic      { enum { value = false }; };
00057 template<> struct is_arithmetic<float>         { enum { value = true }; };
00058 template<> struct is_arithmetic<double>        { enum { value = true }; };
00059 template<> struct is_arithmetic<long double>   { enum { value = true }; };
00060 template<> struct is_arithmetic<bool>          { enum { value = true }; };
00061 template<> struct is_arithmetic<char>          { enum { value = true }; };
00062 template<> struct is_arithmetic<signed char>   { enum { value = true }; };
00063 template<> struct is_arithmetic<unsigned char> { enum { value = true }; };
00064 template<> struct is_arithmetic<signed short>  { enum { value = true }; };
00065 template<> struct is_arithmetic<unsigned short>{ enum { value = true }; };
00066 template<> struct is_arithmetic<signed int>    { enum { value = true }; };
00067 template<> struct is_arithmetic<unsigned int>  { enum { value = true }; };
00068 template<> struct is_arithmetic<signed long>   { enum { value = true }; };
00069 template<> struct is_arithmetic<unsigned long> { enum { value = true }; };
00070 
00071 template <typename T> struct add_const { typedef const T type; };
00072 template <typename T> struct add_const<T&> { typedef T& type; };
00073 
00074 template <typename T> struct is_const { enum { value = 0 }; };
00075 template <typename T> struct is_const<T const> { enum { value = 1 }; };
00076 
00077 template<typename T> struct add_const_on_value_type            { typedef const T type;  };
00078 template<typename T> struct add_const_on_value_type<T&>        { typedef T const& type; };
00079 template<typename T> struct add_const_on_value_type<T*>        { typedef T const* type; };
00080 template<typename T> struct add_const_on_value_type<T* const>  { typedef T const* const type; };
00081 template<typename T> struct add_const_on_value_type<T const* const>  { typedef T const* const type; };
00082 
00083 /** \internal Allows to enable/disable an overload
00084   * according to a compile time condition.
00085   */
00086 template<bool Condition, typename T> struct enable_if;
00087 
00088 template<typename T> struct enable_if<true,T>
00089 { typedef T type; };
00090 
00091 
00092 
00093 /** \internal
00094   * A base class do disable default copy ctor and copy assignement operator.
00095   */
00096 class noncopyable
00097 {
00098   noncopyable(const noncopyable&);
00099   const noncopyable& operator=(const noncopyable&);
00100 protected:
00101   noncopyable() {}
00102   ~noncopyable() {}
00103 };
00104 
00105 
00106 /** \internal
00107   * Convenient struct to get the result type of a unary or binary functor.
00108   *
00109   * It supports both the current STL mechanism (using the result_type member) as well as
00110   * upcoming next STL generation (using a templated result member).
00111   * If none of these members is provided, then the type of the first argument is returned. FIXME, that behavior is a pretty bad hack.
00112   */
00113 template<typename T> struct result_of {};
00114 
00115 struct has_none {int a[1];};
00116 struct has_std_result_type {int a[2];};
00117 struct has_tr1_result {int a[3];};
00118 
00119 template<typename Func, typename ArgType, int SizeOf=sizeof(has_none)>
00120 struct unary_result_of_select {typedef ArgType type;};
00121 
00122 template<typename Func, typename ArgType>
00123 struct unary_result_of_select<Func, ArgType, sizeof(has_std_result_type)> {typedef typename Func::result_type type;};
00124 
00125 template<typename Func, typename ArgType>
00126 struct unary_result_of_select<Func, ArgType, sizeof(has_tr1_result)> {typedef typename Func::template result<Func(ArgType)>::type type;};
00127 
00128 template<typename Func, typename ArgType>
00129 struct result_of<Func(ArgType)> {
00130     template<typename T>
00131     static has_std_result_type testFunctor(T const *, typename T::result_type const * = 0);
00132     template<typename T>
00133     static has_tr1_result      testFunctor(T const *, typename T::template result<T(ArgType)>::type const * = 0);
00134     static has_none            testFunctor(...);
00135 
00136     // note that the following indirection is needed for gcc-3.3
00137     enum {FunctorType = sizeof(testFunctor(static_cast<Func*>(0)))};
00138     typedef typename unary_result_of_select<Func, ArgType, FunctorType>::type type;
00139 };
00140 
00141 template<typename Func, typename ArgType0, typename ArgType1, int SizeOf=sizeof(has_none)>
00142 struct binary_result_of_select {typedef ArgType0 type;};
00143 
00144 template<typename Func, typename ArgType0, typename ArgType1>
00145 struct binary_result_of_select<Func, ArgType0, ArgType1, sizeof(has_std_result_type)>
00146 {typedef typename Func::result_type type;};
00147 
00148 template<typename Func, typename ArgType0, typename ArgType1>
00149 struct binary_result_of_select<Func, ArgType0, ArgType1, sizeof(has_tr1_result)>
00150 {typedef typename Func::template result<Func(ArgType0,ArgType1)>::type type;};
00151 
00152 template<typename Func, typename ArgType0, typename ArgType1>
00153 struct result_of<Func(ArgType0,ArgType1)> {
00154     template<typename T>
00155     static has_std_result_type testFunctor(T const *, typename T::result_type const * = 0);
00156     template<typename T>
00157     static has_tr1_result      testFunctor(T const *, typename T::template result<T(ArgType0,ArgType1)>::type const * = 0);
00158     static has_none            testFunctor(...);
00159 
00160     // note that the following indirection is needed for gcc-3.3
00161     enum {FunctorType = sizeof(testFunctor(static_cast<Func*>(0)))};
00162     typedef typename binary_result_of_select<Func, ArgType0, ArgType1, FunctorType>::type type;
00163 };
00164 
00165 /** \internal In short, it computes int(sqrt(\a Y)) with \a Y an integer.
00166   * Usage example: \code meta_sqrt<1023>::ret \endcode
00167   */
00168 template<int Y,
00169          int InfX = 0,
00170          int SupX = ((Y==1) ? 1 : Y/2),
00171          bool Done = ((SupX-InfX)<=1 ? true : ((SupX*SupX <= Y) && ((SupX+1)*(SupX+1) > Y))) >
00172                                 // use ?: instead of || just to shut up a stupid gcc 4.3 warning
00173 class meta_sqrt
00174 {
00175     enum {
00176       MidX = (InfX+SupX)/2,
00177       TakeInf = MidX*MidX > Y ? 1 : 0,
00178       NewInf = int(TakeInf) ? InfX : int(MidX),
00179       NewSup = int(TakeInf) ? int(MidX) : SupX
00180     };
00181   public:
00182     enum { ret = meta_sqrt<Y,NewInf,NewSup>::ret };
00183 };
00184 
00185 template<int Y, int InfX, int SupX>
00186 class meta_sqrt<Y, InfX, SupX, true> { public:  enum { ret = (SupX*SupX <= Y) ? SupX : InfX }; };
00187 
00188 /** \internal determines whether the product of two numeric types is allowed and what the return type is */
00189 template<typename T, typename U> struct scalar_product_traits
00190 {
00191   enum { Defined = 0 };
00192 };
00193 
00194 template<typename T> struct scalar_product_traits<T,T>
00195 {
00196   enum {
00197     // Cost = NumTraits<T>::MulCost,
00198     Defined = 1
00199   };
00200   typedef T ReturnType;
00201 };
00202 
00203 template<typename T> struct scalar_product_traits<T,std::complex<T> >
00204 {
00205   enum {
00206     // Cost = 2*NumTraits<T>::MulCost,
00207     Defined = 1
00208   };
00209   typedef std::complex<T> ReturnType;
00210 };
00211 
00212 template<typename T> struct scalar_product_traits<std::complex<T>, T>
00213 {
00214   enum {
00215     // Cost = 2*NumTraits<T>::MulCost,
00216     Defined = 1
00217   };
00218   typedef std::complex<T> ReturnType;
00219 };
00220 
00221 // FIXME quick workaround around current limitation of result_of
00222 // template<typename Scalar, typename ArgType0, typename ArgType1>
00223 // struct result_of<scalar_product_op<Scalar>(ArgType0,ArgType1)> {
00224 // typedef typename scalar_product_traits<typename remove_all<ArgType0>::type, typename remove_all<ArgType1>::type>::ReturnType type;
00225 // };
00226 
00227 template<typename T> struct is_diagonal
00228 { enum { ret = false }; };
00229 
00230 template<typename T> struct is_diagonal<DiagonalBase<T> >
00231 { enum { ret = true }; };
00232 
00233 template<typename T> struct is_diagonal<DiagonalWrapper<T> >
00234 { enum { ret = true }; };
00235 
00236 template<typename T, int S> struct is_diagonal<DiagonalMatrix<T,S> >
00237 { enum { ret = true }; };
00238 
00239 } // end namespace internal
00240 
00241 } // end namespace Eigen
00242 
00243 #endif // EIGEN_META_H