Chris@16: // - lambda_traits.hpp --- Boost Lambda Library ----------------------------
Chris@16: //
Chris@16: // Copyright (C) 1999, 2000 Jaakko Jarvi (jaakko.jarvi@cs.utu.fi)
Chris@16: //
Chris@16: // Distributed under the Boost Software License, Version 1.0. (See
Chris@16: // accompanying file LICENSE_1_0.txt or copy at
Chris@16: // http://www.boost.org/LICENSE_1_0.txt)
Chris@16: //
Chris@16: // For more information, see www.boost.org
Chris@16: // -------------------------------------------------------------------------
Chris@16: 
Chris@16: #ifndef BOOST_LAMBDA_LAMBDA_TRAITS_HPP
Chris@16: #define BOOST_LAMBDA_LAMBDA_TRAITS_HPP
Chris@16: 
Chris@16: #include "boost/type_traits/transform_traits.hpp"
Chris@16: #include "boost/type_traits/cv_traits.hpp"
Chris@16: #include "boost/type_traits/function_traits.hpp"
Chris@16: #include "boost/type_traits/object_traits.hpp"
Chris@16: #include "boost/tuple/tuple.hpp"
Chris@16: 
Chris@16: namespace boost {
Chris@16: namespace lambda {
Chris@16: 
Chris@16: // -- if construct ------------------------------------------------
Chris@16: // Proposed by Krzysztof Czarnecki and Ulrich Eisenecker
Chris@16: 
Chris@16: namespace detail {
Chris@16: 
Chris@16: template <bool If, class Then, class Else> struct IF { typedef Then RET; };
Chris@16: 
Chris@16: template <class Then, class Else> struct IF<false, Then, Else> {
Chris@16:   typedef Else RET;
Chris@16: };
Chris@16: 
Chris@16: 
Chris@16: // An if construct that doesn't instantiate the non-matching template:
Chris@16: 
Chris@16: // Called as: 
Chris@16: //  IF_type<condition, A, B>::type 
Chris@16: // The matching template must define the typeded 'type'
Chris@16: // I.e. A::type if condition is true, B::type if condition is false
Chris@16: // Idea from Vesa Karvonen (from C&E as well I guess)
Chris@16: template<class T>
Chris@16: struct IF_type_
Chris@16: {
Chris@16:   typedef typename T::type type;
Chris@16: };
Chris@16: 
Chris@16: 
Chris@16: template<bool C, class T, class E>
Chris@16: struct IF_type
Chris@16: {
Chris@16:   typedef typename
Chris@16:     IF_type_<typename IF<C, T, E>::RET >::type type;
Chris@16: };
Chris@16: 
Chris@16: // helper that can be used to give typedef T to some type
Chris@16: template <class T> struct identity_mapping { typedef T type; };
Chris@16: 
Chris@16: // An if construct for finding an integral constant 'value'
Chris@16: // Does not instantiate the non-matching branch
Chris@16: // Called as IF_value<condition, A, B>::value
Chris@16: // If condition is true A::value must be defined, otherwise B::value
Chris@16: 
Chris@16: template<class T>
Chris@16: struct IF_value_
Chris@16: {
Chris@16:   BOOST_STATIC_CONSTANT(int, value = T::value);
Chris@16: };
Chris@16: 
Chris@16: 
Chris@16: template<bool C, class T, class E>
Chris@16: struct IF_value
Chris@16: {
Chris@16:   BOOST_STATIC_CONSTANT(int, value = (IF_value_<typename IF<C, T, E>::RET>::value));
Chris@16: };
Chris@16: 
Chris@16: 
Chris@16: // --------------------------------------------------------------
Chris@16: 
Chris@16: // removes reference from other than function types:
Chris@16: template<class T> class remove_reference_if_valid
Chris@16: {
Chris@16: 
Chris@16:   typedef typename boost::remove_reference<T>::type plainT;
Chris@16: public:
Chris@16:   typedef typename IF<
Chris@16:     boost::is_function<plainT>::value,
Chris@16:     T,
Chris@16:     plainT
Chris@16:   >::RET type;
Chris@16: 
Chris@16: };
Chris@16: 
Chris@16: 
Chris@16: template<class T> struct remove_reference_and_cv {
Chris@16:    typedef typename boost::remove_cv<
Chris@16:      typename boost::remove_reference<T>::type
Chris@16:    >::type type;
Chris@16: };
Chris@16: 
Chris@16: 
Chris@16:    
Chris@16: // returns a reference to the element of tuple T
Chris@16: template<int N, class T> struct tuple_element_as_reference {   
Chris@16:   typedef typename
Chris@16:      boost::tuples::access_traits<
Chris@16:        typename boost::tuples::element<N, T>::type
Chris@16:      >::non_const_type type;
Chris@16: };
Chris@16: 
Chris@16: // returns the cv and reverence stripped type of a tuple element
Chris@16: template<int N, class T> struct tuple_element_stripped {   
Chris@16:   typedef typename
Chris@16:      remove_reference_and_cv<
Chris@16:        typename boost::tuples::element<N, T>::type
Chris@16:      >::type type;
Chris@16: };
Chris@16: 
Chris@16: // is_lambda_functor -------------------------------------------------   
Chris@16: 
Chris@16: template <class T> struct is_lambda_functor_ {
Chris@16:   BOOST_STATIC_CONSTANT(bool, value = false);
Chris@16: };
Chris@16:    
Chris@16: template <class Arg> struct is_lambda_functor_<lambda_functor<Arg> > {
Chris@16:   BOOST_STATIC_CONSTANT(bool, value = true);
Chris@16: };
Chris@16:    
Chris@16: } // end detail
Chris@16: 
Chris@16:    
Chris@16: template <class T> struct is_lambda_functor {
Chris@16:   BOOST_STATIC_CONSTANT(bool, 
Chris@16:      value = 
Chris@16:        detail::is_lambda_functor_<
Chris@16:          typename detail::remove_reference_and_cv<T>::type
Chris@16:        >::value);
Chris@16: };
Chris@16:    
Chris@16: 
Chris@16: namespace detail {
Chris@16: 
Chris@16: // -- parameter_traits_ ---------------------------------------------
Chris@16: 
Chris@16: // An internal parameter type traits class that respects
Chris@16: // the reference_wrapper class.
Chris@16: 
Chris@16: // The conversions performed are:
Chris@16: // references -> compile_time_error
Chris@16: // T1 -> T2, 
Chris@16: // reference_wrapper<T> -> T&
Chris@16: // const array -> ref to const array
Chris@16: // array -> ref to array
Chris@16: // function -> ref to function
Chris@16: 
Chris@16: // ------------------------------------------------------------------------
Chris@16: 
Chris@16: template<class T1, class T2> 
Chris@16: struct parameter_traits_ {
Chris@16:   typedef T2 type;
Chris@16: };
Chris@16: 
Chris@16: // Do not instantiate with reference types
Chris@16: template<class T, class Any> struct parameter_traits_<T&, Any> {
Chris@16:   typedef typename 
Chris@16:     generate_error<T&>::
Chris@16:       parameter_traits_class_instantiated_with_reference_type type;
Chris@16: };
Chris@16: 
Chris@16: // Arrays can't be stored as plain types; convert them to references
Chris@16: template<class T, int n, class Any> struct parameter_traits_<T[n], Any> {
Chris@16:   typedef T (&type)[n];
Chris@16: };
Chris@16:    
Chris@16: template<class T, int n, class Any> 
Chris@16: struct parameter_traits_<const T[n], Any> {
Chris@16:   typedef const T (&type)[n];
Chris@16: };
Chris@16: 
Chris@16: template<class T, int n, class Any> 
Chris@16: struct parameter_traits_<volatile T[n], Any> {
Chris@16:   typedef volatile  T (&type)[n];
Chris@16: };
Chris@16: template<class T, int n, class Any> 
Chris@16: struct parameter_traits_<const volatile T[n], Any> {
Chris@16:   typedef const volatile T (&type)[n];
Chris@16: };
Chris@16: 
Chris@16: 
Chris@16: template<class T, class Any> 
Chris@16: struct parameter_traits_<boost::reference_wrapper<T>, Any >{
Chris@16:   typedef T& type;
Chris@16: };
Chris@16: 
Chris@16: template<class T, class Any> 
Chris@16: struct parameter_traits_<const boost::reference_wrapper<T>, Any >{
Chris@16:   typedef T& type;
Chris@16: };
Chris@16: 
Chris@16: template<class T, class Any> 
Chris@16: struct parameter_traits_<volatile boost::reference_wrapper<T>, Any >{
Chris@16:   typedef T& type;
Chris@16: };
Chris@16: 
Chris@16: template<class T, class Any> 
Chris@16: struct parameter_traits_<const volatile boost::reference_wrapper<T>, Any >{
Chris@16:   typedef T& type;
Chris@16: };
Chris@16: 
Chris@16: template<class Any>
Chris@16: struct parameter_traits_<void, Any> {
Chris@16:   typedef void type;
Chris@16: };
Chris@16: 
Chris@16: template<class Arg, class Any>
Chris@16: struct parameter_traits_<lambda_functor<Arg>, Any > {
Chris@16:   typedef lambda_functor<Arg> type;
Chris@16: };
Chris@16: 
Chris@16: template<class Arg, class Any>
Chris@16: struct parameter_traits_<const lambda_functor<Arg>, Any > {
Chris@16:   typedef lambda_functor<Arg> type;
Chris@16: };
Chris@16: 
Chris@16: // Are the volatile versions needed?
Chris@16: template<class Arg, class Any>
Chris@16: struct parameter_traits_<volatile lambda_functor<Arg>, Any > {
Chris@16:   typedef lambda_functor<Arg> type;
Chris@16: };
Chris@16: 
Chris@16: template<class Arg, class Any>
Chris@16: struct parameter_traits_<const volatile lambda_functor<Arg>, Any > {
Chris@16:   typedef lambda_functor<Arg> type;
Chris@16: };
Chris@16: 
Chris@16: } // end namespace detail
Chris@16: 
Chris@16: 
Chris@16: // ------------------------------------------------------------------------
Chris@16: // traits classes for lambda expressions (bind functions, operators ...)   
Chris@16: 
Chris@16: // must be instantiated with non-reference types
Chris@16: 
Chris@16: // The default is const plain type -------------------------
Chris@16: // const T -> const T, 
Chris@16: // T -> const T, 
Chris@16: // references -> compile_time_error
Chris@16: // reference_wrapper<T> -> T&
Chris@16: // array -> const ref array
Chris@16: template<class T>
Chris@16: struct const_copy_argument {
Chris@16:   typedef typename 
Chris@16:     detail::parameter_traits_<
Chris@16:       T,
Chris@16:       typename detail::IF<boost::is_function<T>::value, T&, const T>::RET
Chris@16:     >::type type;
Chris@16: };
Chris@16: 
Chris@16: // T may be a function type. Without the IF test, const would be added 
Chris@16: // to a function type, which is illegal.
Chris@16: 
Chris@16: // all arrays are converted to const.
Chris@16: // This traits template is used for 'const T&' parameter passing 
Chris@16: // and thus the knowledge of the potential 
Chris@16: // non-constness of an actual argument is lost.   
Chris@16: template<class T, int n>  struct const_copy_argument <T[n]> {
Chris@16:   typedef const T (&type)[n];
Chris@16: };
Chris@16: template<class T, int n>  struct const_copy_argument <volatile T[n]> {
Chris@16:      typedef const volatile T (&type)[n];
Chris@16: };
Chris@16:    
Chris@16: template<class T>
Chris@16: struct const_copy_argument<T&> {};
Chris@16: // do not instantiate with references
Chris@16:   //  typedef typename detail::generate_error<T&>::references_not_allowed type;
Chris@16: 
Chris@16: 
Chris@16: template<>
Chris@16: struct const_copy_argument<void> {
Chris@16:   typedef void type;
Chris@16: };
Chris@16: 
Chris@16: 
Chris@16: // Does the same as const_copy_argument, but passes references through as such
Chris@16: template<class T>
Chris@16: struct bound_argument_conversion {
Chris@16:   typedef typename const_copy_argument<T>::type type; 
Chris@16: };
Chris@16: 
Chris@16: template<class T>
Chris@16: struct bound_argument_conversion<T&> {
Chris@16:   typedef T& type; 
Chris@16: };
Chris@16:    
Chris@16: // The default is non-const reference -------------------------
Chris@16: // const T -> const T&, 
Chris@16: // T -> T&, 
Chris@16: // references -> compile_time_error
Chris@16: // reference_wrapper<T> -> T&
Chris@16: template<class T>
Chris@16: struct reference_argument {
Chris@16:   typedef typename detail::parameter_traits_<T, T&>::type type; 
Chris@16: };
Chris@16: 
Chris@16: template<class T>
Chris@16: struct reference_argument<T&> {
Chris@16:   typedef typename detail::generate_error<T&>::references_not_allowed type; 
Chris@16: };
Chris@16: 
Chris@16: template<class Arg>
Chris@16: struct reference_argument<lambda_functor<Arg> > {
Chris@16:   typedef lambda_functor<Arg> type;
Chris@16: };
Chris@16: 
Chris@16: template<class Arg>
Chris@16: struct reference_argument<const lambda_functor<Arg> > {
Chris@16:   typedef lambda_functor<Arg> type;
Chris@16: };
Chris@16: 
Chris@16: // Are the volatile versions needed?
Chris@16: template<class Arg>
Chris@16: struct reference_argument<volatile lambda_functor<Arg> > {
Chris@16:   typedef lambda_functor<Arg> type;
Chris@16: };
Chris@16: 
Chris@16: template<class Arg>
Chris@16: struct reference_argument<const volatile lambda_functor<Arg> > {
Chris@16:   typedef lambda_functor<Arg> type;
Chris@16: };
Chris@16: 
Chris@16: template<>
Chris@16: struct reference_argument<void> {
Chris@16:   typedef void type;
Chris@16: };
Chris@16: 
Chris@16: namespace detail {
Chris@16:    
Chris@16: // Array to pointer conversion
Chris@16: template <class T>
Chris@16: struct array_to_pointer { 
Chris@16:   typedef T type;
Chris@16: };
Chris@16: 
Chris@16: template <class T, int N>
Chris@16: struct array_to_pointer <const T[N]> { 
Chris@16:   typedef const T* type;
Chris@16: };
Chris@16: template <class T, int N>
Chris@16: struct array_to_pointer <T[N]> { 
Chris@16:   typedef T* type;
Chris@16: };
Chris@16: 
Chris@16: template <class T, int N>
Chris@16: struct array_to_pointer <const T (&) [N]> { 
Chris@16:   typedef const T* type;
Chris@16: };
Chris@16: template <class T, int N>
Chris@16: struct array_to_pointer <T (&) [N]> { 
Chris@16:   typedef T* type;
Chris@16: };
Chris@16: 
Chris@16: 
Chris@16: // ---------------------------------------------------------------------------
Chris@16: // The call_traits for bind
Chris@16: // Respects the reference_wrapper class.
Chris@16: 
Chris@16: // These templates are used outside of bind functions as well.
Chris@16: // the bind_tuple_mapper provides a shorter notation for default
Chris@16: // bound argument storing semantics, if all arguments are treated
Chris@16: // uniformly.
Chris@16: 
Chris@16: // from template<class T> foo(const T& t) : bind_traits<const T>::type
Chris@16: // from template<class T> foo(T& t) : bind_traits<T>::type
Chris@16: 
Chris@16: // Conversions:
Chris@16: // T -> const T,
Chris@16: // cv T -> cv T, 
Chris@16: // T& -> T& 
Chris@16: // reference_wrapper<T> -> T&
Chris@16: // const reference_wrapper<T> -> T&
Chris@16: // array -> const ref array
Chris@16: 
Chris@16: // make bound arguments const, this is a deliberate design choice, the
Chris@16: // purpose is to prevent side effects to bound arguments that are stored
Chris@16: // as copies
Chris@16: template<class T>
Chris@16: struct bind_traits {
Chris@16:   typedef const T type; 
Chris@16: };
Chris@16: 
Chris@16: template<class T>
Chris@16: struct bind_traits<T&> {
Chris@16:   typedef T& type; 
Chris@16: };
Chris@16: 
Chris@16: // null_types are an exception, we always want to store them as non const
Chris@16: // so that other templates can assume that null_type is always without const
Chris@16: template<>
Chris@16: struct bind_traits<null_type> {
Chris@16:   typedef null_type type;
Chris@16: };
Chris@16: 
Chris@16: // the bind_tuple_mapper, bind_type_generators may 
Chris@16: // introduce const to null_type
Chris@16: template<>
Chris@16: struct bind_traits<const null_type> {
Chris@16:   typedef null_type type;
Chris@16: };
Chris@16: 
Chris@16: // Arrays can't be stored as plain types; convert them to references.
Chris@16: // All arrays are converted to const. This is because bind takes its
Chris@16: // parameters as const T& and thus the knowledge of the potential 
Chris@16: // non-constness of actual argument is lost.
Chris@16: template<class T, int n>  struct bind_traits <T[n]> {
Chris@16:   typedef const T (&type)[n];
Chris@16: };
Chris@16: 
Chris@16: template<class T, int n> 
Chris@16: struct bind_traits<const T[n]> {
Chris@16:   typedef const T (&type)[n];
Chris@16: };
Chris@16: 
Chris@16: template<class T, int n>  struct bind_traits<volatile T[n]> {
Chris@16:   typedef const volatile T (&type)[n];
Chris@16: };
Chris@16: 
Chris@16: template<class T, int n> 
Chris@16: struct bind_traits<const volatile T[n]> {
Chris@16:   typedef const volatile T (&type)[n];
Chris@16: };
Chris@16: 
Chris@16: template<class R>
Chris@16: struct bind_traits<R()> {
Chris@16:     typedef R(&type)();
Chris@16: };
Chris@16: 
Chris@16: template<class R, class Arg1>
Chris@16: struct bind_traits<R(Arg1)> {
Chris@16:     typedef R(&type)(Arg1);
Chris@16: };
Chris@16: 
Chris@16: template<class R, class Arg1, class Arg2>
Chris@16: struct bind_traits<R(Arg1, Arg2)> {
Chris@16:     typedef R(&type)(Arg1, Arg2);
Chris@16: };
Chris@16: 
Chris@16: template<class R, class Arg1, class Arg2, class Arg3>
Chris@16: struct bind_traits<R(Arg1, Arg2, Arg3)> {
Chris@16:     typedef R(&type)(Arg1, Arg2, Arg3);
Chris@16: };
Chris@16: 
Chris@16: template<class R, class Arg1, class Arg2, class Arg3, class Arg4>
Chris@16: struct bind_traits<R(Arg1, Arg2, Arg3, Arg4)> {
Chris@16:     typedef R(&type)(Arg1, Arg2, Arg3, Arg4);
Chris@16: };
Chris@16: 
Chris@16: template<class R, class Arg1, class Arg2, class Arg3, class Arg4, class Arg5>
Chris@16: struct bind_traits<R(Arg1, Arg2, Arg3, Arg4, Arg5)> {
Chris@16:     typedef R(&type)(Arg1, Arg2, Arg3, Arg4, Arg5);
Chris@16: };
Chris@16: 
Chris@16: template<class R, class Arg1, class Arg2, class Arg3, class Arg4, class Arg5, class Arg6>
Chris@16: struct bind_traits<R(Arg1, Arg2, Arg3, Arg4, Arg5, Arg6)> {
Chris@16:     typedef R(&type)(Arg1, Arg2, Arg3, Arg4, Arg5, Arg6);
Chris@16: };
Chris@16: 
Chris@16: template<class R, class Arg1, class Arg2, class Arg3, class Arg4, class Arg5, class Arg6, class Arg7>
Chris@16: struct bind_traits<R(Arg1, Arg2, Arg3, Arg4, Arg5, Arg6, Arg7)> {
Chris@16:     typedef R(&type)(Arg1, Arg2, Arg3, Arg4, Arg5, Arg6, Arg7);
Chris@16: };
Chris@16: 
Chris@16: template<class R, class Arg1, class Arg2, class Arg3, class Arg4, class Arg5, class Arg6, class Arg7, class Arg8>
Chris@16: struct bind_traits<R(Arg1, Arg2, Arg3, Arg4, Arg5, Arg6, Arg7, Arg8)> {
Chris@16:     typedef R(&type)(Arg1, Arg2, Arg3, Arg4, Arg5, Arg6, Arg7, Arg8);
Chris@16: };
Chris@16: 
Chris@16: template<class R, class Arg1, class Arg2, class Arg3, class Arg4, class Arg5, class Arg6, class Arg7, class Arg8, class Arg9>
Chris@16: struct bind_traits<R(Arg1, Arg2, Arg3, Arg4, Arg5, Arg6, Arg7, Arg8, Arg9)> {
Chris@16:     typedef R(&type)(Arg1, Arg2, Arg3, Arg4, Arg5, Arg6, Arg7, Arg8, Arg9);
Chris@16: };
Chris@16: 
Chris@16: template<class T> 
Chris@16: struct bind_traits<reference_wrapper<T> >{
Chris@16:   typedef T& type;
Chris@16: };
Chris@16: 
Chris@16: template<class T> 
Chris@16: struct bind_traits<const reference_wrapper<T> >{
Chris@16:   typedef T& type;
Chris@16: };
Chris@16: 
Chris@16: template<>
Chris@16: struct bind_traits<void> {
Chris@16:   typedef void type;
Chris@16: };
Chris@16: 
Chris@16: 
Chris@16: 
Chris@16: template <
Chris@16:   class T0 = null_type, class T1 = null_type, class T2 = null_type, 
Chris@16:   class T3 = null_type, class T4 = null_type, class T5 = null_type, 
Chris@16:   class T6 = null_type, class T7 = null_type, class T8 = null_type, 
Chris@16:   class T9 = null_type
Chris@16: >
Chris@16: struct bind_tuple_mapper {
Chris@16:   typedef
Chris@16:     tuple<typename bind_traits<T0>::type, 
Chris@16:           typename bind_traits<T1>::type, 
Chris@16:           typename bind_traits<T2>::type, 
Chris@16:           typename bind_traits<T3>::type, 
Chris@16:           typename bind_traits<T4>::type, 
Chris@16:           typename bind_traits<T5>::type, 
Chris@16:           typename bind_traits<T6>::type, 
Chris@16:           typename bind_traits<T7>::type,
Chris@16:           typename bind_traits<T8>::type,
Chris@16:           typename bind_traits<T9>::type> type;
Chris@16: };
Chris@16: 
Chris@16: // bind_traits, except map const T& -> const T
Chris@16:   // this is needed e.g. in currying. Const reference arguments can
Chris@16:   // refer to temporaries, so it is not safe to store them as references.
Chris@16:   template <class T> struct remove_const_reference {
Chris@16:     typedef typename bind_traits<T>::type type;
Chris@16:   };
Chris@16: 
Chris@16:   template <class T> struct remove_const_reference<const T&> {
Chris@16:     typedef const T type;
Chris@16:   };
Chris@16: 
Chris@16: 
Chris@16: // maps the bind argument types to the resulting lambda functor type
Chris@16: template <
Chris@16:   class T0 = null_type, class T1 = null_type, class T2 = null_type, 
Chris@16:   class T3 = null_type, class T4 = null_type, class T5 = null_type, 
Chris@16:   class T6 = null_type, class T7 = null_type, class T8 = null_type, 
Chris@16:   class T9 = null_type
Chris@16: >
Chris@16: class bind_type_generator {
Chris@16: 
Chris@16:   typedef typename
Chris@16:   detail::bind_tuple_mapper<
Chris@16:     T0, T1, T2, T3, T4, T5, T6, T7, T8, T9
Chris@16:   >::type args_t;
Chris@16: 
Chris@16:   BOOST_STATIC_CONSTANT(int, nof_elems = boost::tuples::length<args_t>::value);
Chris@16: 
Chris@16:   typedef 
Chris@16:     action<
Chris@16:       nof_elems, 
Chris@16:       function_action<nof_elems>
Chris@16:     > action_type;
Chris@16: 
Chris@16: public:
Chris@16:   typedef
Chris@16:     lambda_functor<
Chris@16:       lambda_functor_base<
Chris@16:         action_type, 
Chris@16:         args_t
Chris@16:       >
Chris@16:     > type; 
Chris@16:     
Chris@16: };
Chris@16: 
Chris@16: 
Chris@16:    
Chris@16: } // detail
Chris@16:    
Chris@16: template <class T> inline const T&  make_const(const T& t) { return t; }
Chris@16: 
Chris@16: 
Chris@16: } // end of namespace lambda
Chris@16: } // end of namespace boost
Chris@16: 
Chris@16: 
Chris@16:    
Chris@16: #endif // BOOST_LAMBDA_TRAITS_HPP