boost/lambda/detail/operator_return_type_traits.hpp
// operator_return_type_traits.hpp -- Boost Lambda Library ------------------ // Copyright (C) 1999, 2000 Jaakko Jarvi (jaakko.jarvi@cs.utu.fi) // // Distributed under the Boost Software License, Version 1.0. (See // accompanying file LICENSE_1_0.txt or copy at // http://www.boost.org/LICENSE_1_0.txt) // // For more information, see www.boost.org #ifndef BOOST_LAMBDA_OPERATOR_RETURN_TYPE_TRAITS_HPP #define BOOST_LAMBDA_OPERATOR_RETURN_TYPE_TRAITS_HPP #include "boost/lambda/detail/is_instance_of.hpp" #include "boost/type_traits/same_traits.hpp" #include "boost/indirect_reference.hpp" #include "boost/detail/container_fwd.hpp" #include <cstddef> // needed for the ptrdiff_t #include <iosfwd> // for istream and ostream #include <iterator> // needed for operator& namespace boost { namespace lambda { namespace detail { // -- general helper templates for type deduction ------------------ // Much of the type deduction code for standard arithmetic types from Gary Powell template <class A> struct promote_code { static const int value = -1; }; // this means that a code is not defined for A // -- the next 5 types are needed in if_then_else_return // the promotion order is not important, but they must have distinct values. template <> struct promote_code<bool> { static const int value = 10; }; template <> struct promote_code<char> { static const int value = 20; }; template <> struct promote_code<unsigned char> { static const int value = 30; }; template <> struct promote_code<signed char> { static const int value = 40; }; template <> struct promote_code<short int> { static const int value = 50; }; // ---------- template <> struct promote_code<int> { static const int value = 100; }; template <> struct promote_code<unsigned int> { static const int value = 200; }; template <> struct promote_code<long> { static const int value = 300; }; template <> struct promote_code<unsigned long> { static const int value = 400; }; template <> struct promote_code<float> { static const int value = 500; }; template <> struct promote_code<double> { static const int value = 600; }; template <> struct promote_code<long double> { static const int value = 700; }; // TODO: wchar_t // forward delcaration of complex. } // namespace detail } // namespace lambda } // namespace boost namespace boost { namespace lambda { namespace detail { template <> struct promote_code< std::complex<float> > { static const int value = 800; }; template <> struct promote_code< std::complex<double> > { static const int value = 900; }; template <> struct promote_code< std::complex<long double> > { static const int value = 1000; }; // -- int promotion ------------------------------------------- template <class T> struct promote_to_int { typedef T type; }; template <> struct promote_to_int<bool> { typedef int type; }; template <> struct promote_to_int<char> { typedef int type; }; template <> struct promote_to_int<unsigned char> { typedef int type; }; template <> struct promote_to_int<signed char> { typedef int type; }; template <> struct promote_to_int<short int> { typedef int type; }; // The unsigned short int promotion rule is this: // unsigned short int to signed int if a signed int can hold all values // of unsigned short int, otherwise go to unsigned int. template <> struct promote_to_int<unsigned short int> { typedef detail::IF<sizeof(int) <= sizeof(unsigned short int), // I had the logic reversed but ">" messes up the parsing. unsigned int, int>::RET type; }; // TODO: think, should there be default behaviour for non-standard types? } // namespace detail // ------------------------------------------ // Unary actions ---------------------------- // ------------------------------------------ template<class Act, class A> struct plain_return_type_1 { typedef detail::unspecified type; }; template<class Act, class A> struct plain_return_type_1<unary_arithmetic_action<Act>, A> { typedef A type; }; template<class Act, class A> struct return_type_1<unary_arithmetic_action<Act>, A> { typedef typename plain_return_type_1< unary_arithmetic_action<Act>, typename detail::remove_reference_and_cv<A>::type >::type type; }; template<class A> struct plain_return_type_1<bitwise_action<not_action>, A> { typedef A type; }; // bitwise not, operator~() template<class A> struct return_type_1<bitwise_action<not_action>, A> { typedef typename plain_return_type_1< bitwise_action<not_action>, typename detail::remove_reference_and_cv<A>::type >::type type; }; // prefix increment and decrement operators return // their argument by default as a non-const reference template<class Act, class A> struct plain_return_type_1<pre_increment_decrement_action<Act>, A> { typedef A& type; }; template<class Act, class A> struct return_type_1<pre_increment_decrement_action<Act>, A> { typedef typename plain_return_type_1< pre_increment_decrement_action<Act>, typename detail::remove_reference_and_cv<A>::type >::type type; }; // post decrement just returns the same plain type. template<class Act, class A> struct plain_return_type_1<post_increment_decrement_action<Act>, A> { typedef A type; }; template<class Act, class A> struct return_type_1<post_increment_decrement_action<Act>, A> { typedef typename plain_return_type_1< post_increment_decrement_action<Act>, typename detail::remove_reference_and_cv<A>::type >::type type; }; // logical not, operator!() template<class A> struct plain_return_type_1<logical_action<not_action>, A> { typedef bool type; }; template<class A> struct return_type_1<logical_action<not_action>, A> { typedef typename plain_return_type_1< logical_action<not_action>, typename detail::remove_reference_and_cv<A>::type >::type type; }; // address of action --------------------------------------- template<class A> struct return_type_1<other_action<addressof_action>, A> { typedef typename plain_return_type_1< other_action<addressof_action>, typename detail::remove_reference_and_cv<A>::type >::type type1; // If no user defined specialization for A, then return the // cv qualified pointer to A typedef typename detail::IF< boost::is_same<type1, detail::unspecified>::value, typename boost::remove_reference<A>::type*, type1 >::RET type; }; // contentsof action ------------------------------------ // TODO: this deduction may lead to fail directly, // (if A has no specialization for iterator_traits and has no // typedef A::reference. // There is no easy way around this, cause there doesn't seem to be a way // to test whether a class is an iterator or not. // The default works with std::iterators. namespace detail { // A is a nonreference type template <class A> struct contentsof_type { typedef typename boost::indirect_reference<A>::type type; }; // this is since the nullary () in lambda_functor is always instantiated template <> struct contentsof_type<null_type> { typedef detail::unspecified type; }; template <class A> struct contentsof_type<const A> { typedef typename contentsof_type<A>::type type; }; template <class A> struct contentsof_type<volatile A> { typedef typename contentsof_type<A>::type type; }; template <class A> struct contentsof_type<const volatile A> { typedef typename contentsof_type<A>::type type; }; // standard iterator traits should take care of the pointer types // but just to be on the safe side, we have the specializations here: // these work even if A is cv-qualified. template <class A> struct contentsof_type<A*> { typedef A& type; }; template <class A> struct contentsof_type<A* const> { typedef A& type; }; template <class A> struct contentsof_type<A* volatile> { typedef A& type; }; template <class A> struct contentsof_type<A* const volatile> { typedef A& type; }; template<class A, int N> struct contentsof_type<A[N]> { typedef A& type; }; template<class A, int N> struct contentsof_type<const A[N]> { typedef const A& type; }; template<class A, int N> struct contentsof_type<volatile A[N]> { typedef volatile A& type; }; template<class A, int N> struct contentsof_type<const volatile A[N]> { typedef const volatile A& type; }; } // end detail template<class A> struct return_type_1<other_action<contentsof_action>, A> { typedef typename plain_return_type_1< other_action<contentsof_action>, typename detail::remove_reference_and_cv<A>::type >::type type1; // If no user defined specialization for A, then return the // cv qualified pointer to A typedef typename detail::IF_type< boost::is_same<type1, detail::unspecified>::value, detail::contentsof_type< typename boost::remove_reference<A>::type >, detail::identity_mapping<type1> >::type type; }; // ------------------------------------------------------------------ // binary actions --------------------------------------------------- // ------------------------------------------------------------------ // here the default case is: no user defined versions: template <class Act, class A, class B> struct plain_return_type_2 { typedef detail::unspecified type; }; namespace detail { // error classes class illegal_pointer_arithmetic{}; // pointer arithmetic type deductions ---------------------- // value = false means that this is not a pointer arithmetic case // value = true means, that this can be a pointer arithmetic case, but not necessarily is // This means, that for user defined operators for pointer types, say for some operator+(X, *Y), // the deductions must be coded at an earliel level (return_type_2). template<class Act, class A, class B> struct pointer_arithmetic_traits { static const bool value = false; }; template<class A, class B> struct pointer_arithmetic_traits<plus_action, A, B> { typedef typename array_to_pointer<typename boost::remove_reference<A>::type>::type AP; typedef typename array_to_pointer<typename boost::remove_reference<B>::type>::type BP; static const bool is_pointer_A = boost::is_pointer<AP>::value; static const bool is_pointer_B = boost::is_pointer<BP>::value; static const bool value = is_pointer_A || is_pointer_B; // can't add two pointers. // note, that we do not check wether the other type is valid for // addition with a pointer. // the compiler will catch it in the apply function typedef typename detail::IF< is_pointer_A && is_pointer_B, detail::return_type_deduction_failure< detail::illegal_pointer_arithmetic >, typename detail::IF<is_pointer_A, AP, BP>::RET >::RET type; }; template<class A, class B> struct pointer_arithmetic_traits<minus_action, A, B> { typedef typename array_to_pointer<typename boost::remove_reference<A>::type>::type AP; typedef typename array_to_pointer<typename boost::remove_reference<B>::type>::type BP; static const bool is_pointer_A = boost::is_pointer<AP>::value; static const bool is_pointer_B = boost::is_pointer<BP>::value; static const bool value = is_pointer_A || is_pointer_B; static const bool same_pointer_type = is_pointer_A && is_pointer_B && boost::is_same< typename boost::remove_const< typename boost::remove_pointer< typename boost::remove_const<AP>::type >::type >::type, typename boost::remove_const< typename boost::remove_pointer< typename boost::remove_const<BP>::type >::type >::type >::value; // ptr - ptr has type ptrdiff_t // note, that we do not check if, in ptr - B, B is // valid for subtraction with a pointer. // the compiler will catch it in the apply function typedef typename detail::IF< same_pointer_type, const std::ptrdiff_t, typename detail::IF< is_pointer_A, AP, detail::return_type_deduction_failure<detail::illegal_pointer_arithmetic> >::RET >::RET type; }; } // namespace detail // -- arithmetic actions --------------------------------------------- namespace detail { template<bool is_pointer_arithmetic, class Act, class A, class B> struct return_type_2_arithmetic_phase_1; template<class A, class B> struct return_type_2_arithmetic_phase_2; template<class A, class B> struct return_type_2_arithmetic_phase_3; } // namespace detail // drop any qualifiers from the argument types within arithmetic_action template<class A, class B, class Act> struct return_type_2<arithmetic_action<Act>, A, B> { typedef typename detail::remove_reference_and_cv<A>::type plain_A; typedef typename detail::remove_reference_and_cv<B>::type plain_B; typedef typename plain_return_type_2<arithmetic_action<Act>, plain_A, plain_B>::type type1; // if user defined return type, do not enter the whole arithmetic deductions typedef typename detail::IF_type< boost::is_same<type1, detail::unspecified>::value, detail::return_type_2_arithmetic_phase_1< detail::pointer_arithmetic_traits<Act, A, B>::value, Act, A, B >, plain_return_type_2<arithmetic_action<Act>, plain_A, plain_B> >::type type; }; namespace detail { // perform integral promotion, no pointer arithmetic template<bool is_pointer_arithmetic, class Act, class A, class B> struct return_type_2_arithmetic_phase_1 { typedef typename return_type_2_arithmetic_phase_2< typename remove_reference_and_cv<A>::type, typename remove_reference_and_cv<B>::type >::type type; }; // pointer_arithmetic template<class Act, class A, class B> struct return_type_2_arithmetic_phase_1<true, Act, A, B> { typedef typename pointer_arithmetic_traits<Act, A, B>::type type; }; template<class A, class B> struct return_type_2_arithmetic_phase_2 { typedef typename return_type_2_arithmetic_phase_3< typename promote_to_int<A>::type, typename promote_to_int<B>::type >::type type; }; // specialization for unsigned int. // We only have to do these two specialization because the value promotion will // take care of the other cases. // The unsigned int promotion rule is this: // unsigned int to long if a long can hold all values of unsigned int, // otherwise go to unsigned long. // struct so I don't have to type this twice. struct promotion_of_unsigned_int { typedef detail::IF<sizeof(long) <= sizeof(unsigned int), unsigned long, long>::RET type; }; template<> struct return_type_2_arithmetic_phase_2<unsigned int, long> { typedef promotion_of_unsigned_int::type type; }; template<> struct return_type_2_arithmetic_phase_2<long, unsigned int> { typedef promotion_of_unsigned_int::type type; }; template<class A, class B> struct return_type_2_arithmetic_phase_3 { enum { promote_code_A_value = promote_code<A>::value, promote_code_B_value = promote_code<B>::value }; // enums for KCC typedef typename detail::IF< promote_code_A_value == -1 || promote_code_B_value == -1, detail::return_type_deduction_failure<return_type_2_arithmetic_phase_3>, typename detail::IF< ((int)promote_code_A_value > (int)promote_code_B_value), A, B >::RET >::RET type; }; } // namespace detail // -- bitwise actions ------------------------------------------- // note: for integral types deuduction is similar to arithmetic actions. // drop any qualifiers from the argument types within arithmetic action template<class A, class B, class Act> struct return_type_2<bitwise_action<Act>, A, B> { typedef typename detail::remove_reference_and_cv<A>::type plain_A; typedef typename detail::remove_reference_and_cv<B>::type plain_B; typedef typename plain_return_type_2<bitwise_action<Act>, plain_A, plain_B>::type type1; // if user defined return type, do not enter type deductions typedef typename detail::IF_type< boost::is_same<type1, detail::unspecified>::value, return_type_2<arithmetic_action<plus_action>, A, B>, plain_return_type_2<bitwise_action<Act>, plain_A, plain_B> >::type type; // plus_action is just a random pick, has to be a concrete instance // TODO: This check is only valid for built-in types, overloaded types might // accept floating point operators // bitwise operators not defined for floating point types // these test are not strictly needed here, since the error will be caught in // the apply function BOOST_STATIC_ASSERT(!(boost::is_float<plain_A>::value && boost::is_float<plain_B>::value)); }; namespace detail { #ifdef BOOST_NO_TEMPLATED_STREAMS template<class A, class B> struct leftshift_type { typedef typename detail::IF< boost::is_convertible< typename boost::remove_reference<A>::type*, std::ostream* >::value, std::ostream&, typename detail::remove_reference_and_cv<A>::type >::RET type; }; template<class A, class B> struct rightshift_type { typedef typename detail::IF< boost::is_convertible< typename boost::remove_reference<A>::type*, std::istream* >::value, std::istream&, typename detail::remove_reference_and_cv<A>::type >::RET type; }; #else template <class T> struct get_ostream_type { typedef std::basic_ostream<typename T::char_type, typename T::traits_type>& type; }; template <class T> struct get_istream_type { typedef std::basic_istream<typename T::char_type, typename T::traits_type>& type; }; template<class A, class B> struct leftshift_type { private: typedef typename boost::remove_reference<A>::type plainA; public: typedef typename detail::IF_type< is_instance_of_2<plainA, std::basic_ostream>::value, get_ostream_type<plainA>, //reference to the stream detail::remove_reference_and_cv<A> >::type type; }; template<class A, class B> struct rightshift_type { private: typedef typename boost::remove_reference<A>::type plainA; public: typedef typename detail::IF_type< is_instance_of_2<plainA, std::basic_istream>::value, get_istream_type<plainA>, //reference to the stream detail::remove_reference_and_cv<A> >::type type; }; #endif } // end detail // ostream template<class A, class B> struct return_type_2<bitwise_action<leftshift_action>, A, B> { typedef typename detail::remove_reference_and_cv<A>::type plain_A; typedef typename detail::remove_reference_and_cv<B>::type plain_B; typedef typename plain_return_type_2<bitwise_action<leftshift_action>, plain_A, plain_B>::type type1; // if user defined return type, do not enter type deductions typedef typename detail::IF_type< boost::is_same<type1, detail::unspecified>::value, detail::leftshift_type<A, B>, plain_return_type_2<bitwise_action<leftshift_action>, plain_A, plain_B> >::type type; }; // istream template<class A, class B> struct return_type_2<bitwise_action<rightshift_action>, A, B> { typedef typename detail::remove_reference_and_cv<A>::type plain_A; typedef typename detail::remove_reference_and_cv<B>::type plain_B; typedef typename plain_return_type_2<bitwise_action<rightshift_action>, plain_A, plain_B>::type type1; // if user defined return type, do not enter type deductions typedef typename detail::IF_type< boost::is_same<type1, detail::unspecified>::value, detail::rightshift_type<A, B>, plain_return_type_2<bitwise_action<rightshift_action>, plain_A, plain_B> >::type type; }; // -- logical actions ---------------------------------------- // always bool // NOTE: this may not be true for some weird user-defined types, template<class A, class B, class Act> struct plain_return_type_2<logical_action<Act>, A, B> { typedef bool type; }; template<class A, class B, class Act> struct return_type_2<logical_action<Act>, A, B> { typedef typename detail::remove_reference_and_cv<A>::type plain_A; typedef typename detail::remove_reference_and_cv<B>::type plain_B; typedef typename plain_return_type_2<logical_action<Act>, plain_A, plain_B>::type type; }; // -- relational actions ---------------------------------------- // always bool // NOTE: this may not be true for some weird user-defined types, template<class A, class B, class Act> struct plain_return_type_2<relational_action<Act>, A, B> { typedef bool type; }; template<class A, class B, class Act> struct return_type_2<relational_action<Act>, A, B> { typedef typename detail::remove_reference_and_cv<A>::type plain_A; typedef typename detail::remove_reference_and_cv<B>::type plain_B; typedef typename plain_return_type_2<relational_action<Act>, plain_A, plain_B>::type type; }; // Assingment actions ----------------------------------------------- // return type is the type of the first argument as reference // note that cv-qualifiers are preserved. // Yes, assignment operator can be const! // NOTE: this may not be true for some weird user-defined types, template<class A, class B, class Act> struct return_type_2<arithmetic_assignment_action<Act>, A, B> { typedef typename detail::remove_reference_and_cv<A>::type plain_A; typedef typename detail::remove_reference_and_cv<B>::type plain_B; typedef typename plain_return_type_2< arithmetic_assignment_action<Act>, plain_A, plain_B >::type type1; typedef typename detail::IF< boost::is_same<type1, detail::unspecified>::value, typename boost::add_reference<A>::type, type1 >::RET type; }; template<class A, class B, class Act> struct return_type_2<bitwise_assignment_action<Act>, A, B> { typedef typename detail::remove_reference_and_cv<A>::type plain_A; typedef typename detail::remove_reference_and_cv<B>::type plain_B; typedef typename plain_return_type_2< bitwise_assignment_action<Act>, plain_A, plain_B >::type type1; typedef typename detail::IF< boost::is_same<type1, detail::unspecified>::value, typename boost::add_reference<A>::type, type1 >::RET type; }; template<class A, class B> struct return_type_2<other_action<assignment_action>, A, B> { typedef typename detail::remove_reference_and_cv<A>::type plain_A; typedef typename detail::remove_reference_and_cv<B>::type plain_B; typedef typename plain_return_type_2< other_action<assignment_action>, plain_A, plain_B >::type type1; typedef typename detail::IF< boost::is_same<type1, detail::unspecified>::value, typename boost::add_reference<A>::type, type1 >::RET type; }; // -- other actions ---------------------------------------- // comma action ---------------------------------- // Note: this may not be true for some weird user-defined types, // NOTE! This only tries the plain_return_type_2 layer and gives // detail::unspecified as default. If no such specialization is found, the // type rule in the spcecialization of the return_type_2_prot is used // to give the type of the right argument (which can be a reference too) // (The built in operator, can return a l- or rvalue). template<class A, class B> struct return_type_2<other_action<comma_action>, A, B> { typedef typename detail::remove_reference_and_cv<A>::type plain_A; typedef typename detail::remove_reference_and_cv<B>::type plain_B; typedef typename plain_return_type_2< other_action<comma_action>, plain_A, plain_B >::type type; }; // subscript action ----------------------------------------------- namespace detail { // A and B are nonreference types template <class A, class B> struct subscript_type { typedef detail::unspecified type; }; template <class A, class B> struct subscript_type<A*, B> { typedef A& type; }; template <class A, class B> struct subscript_type<A* const, B> { typedef A& type; }; template <class A, class B> struct subscript_type<A* volatile, B> { typedef A& type; }; template <class A, class B> struct subscript_type<A* const volatile, B> { typedef A& type; }; template<class A, class B, int N> struct subscript_type<A[N], B> { typedef A& type; }; // these 3 specializations are needed to make gcc <3 happy template<class A, class B, int N> struct subscript_type<const A[N], B> { typedef const A& type; }; template<class A, class B, int N> struct subscript_type<volatile A[N], B> { typedef volatile A& type; }; template<class A, class B, int N> struct subscript_type<const volatile A[N], B> { typedef const volatile A& type; }; } // end detail template<class A, class B> struct return_type_2<other_action<subscript_action>, A, B> { typedef typename detail::remove_reference_and_cv<A>::type plain_A; typedef typename detail::remove_reference_and_cv<B>::type plain_B; typedef typename boost::remove_reference<A>::type nonref_A; typedef typename boost::remove_reference<B>::type nonref_B; typedef typename plain_return_type_2< other_action<subscript_action>, plain_A, plain_B >::type type1; typedef typename detail::IF_type< boost::is_same<type1, detail::unspecified>::value, detail::subscript_type<nonref_A, nonref_B>, plain_return_type_2<other_action<subscript_action>, plain_A, plain_B> >::type type; }; template<class Key, class T, class Cmp, class Allocator, class B> struct plain_return_type_2<other_action<subscript_action>, std::map<Key, T, Cmp, Allocator>, B> { typedef T& type; // T == std::map<Key, T, Cmp, Allocator>::mapped_type; }; template<class Key, class T, class Cmp, class Allocator, class B> struct plain_return_type_2<other_action<subscript_action>, std::multimap<Key, T, Cmp, Allocator>, B> { typedef T& type; // T == std::map<Key, T, Cmp, Allocator>::mapped_type; }; // deque template<class T, class Allocator, class B> struct plain_return_type_2<other_action<subscript_action>, std::deque<T, Allocator>, B> { typedef typename std::deque<T, Allocator>::reference type; }; template<class T, class Allocator, class B> struct plain_return_type_2<other_action<subscript_action>, const std::deque<T, Allocator>, B> { typedef typename std::deque<T, Allocator>::const_reference type; }; // vector template<class T, class Allocator, class B> struct plain_return_type_2<other_action<subscript_action>, std::vector<T, Allocator>, B> { typedef typename std::vector<T, Allocator>::reference type; }; template<class T, class Allocator, class B> struct plain_return_type_2<other_action<subscript_action>, const std::vector<T, Allocator>, B> { typedef typename std::vector<T, Allocator>::const_reference type; }; // basic_string template<class Char, class Traits, class Allocator, class B> struct plain_return_type_2<other_action<subscript_action>, std::basic_string<Char, Traits, Allocator>, B> { typedef typename std::basic_string<Char, Traits, Allocator>::reference type; }; template<class Char, class Traits, class Allocator, class B> struct plain_return_type_2<other_action<subscript_action>, const std::basic_string<Char, Traits, Allocator>, B> { typedef typename std::basic_string<Char, Traits, Allocator>::const_reference type; }; template<class Char, class Traits, class Allocator> struct plain_return_type_2<arithmetic_action<plus_action>, std::basic_string<Char, Traits, Allocator>, std::basic_string<Char, Traits, Allocator> > { typedef std::basic_string<Char, Traits, Allocator> type; }; template<class Char, class Traits, class Allocator> struct plain_return_type_2<arithmetic_action<plus_action>, const Char*, std::basic_string<Char, Traits, Allocator> > { typedef std::basic_string<Char, Traits, Allocator> type; }; template<class Char, class Traits, class Allocator> struct plain_return_type_2<arithmetic_action<plus_action>, std::basic_string<Char, Traits, Allocator>, const Char*> { typedef std::basic_string<Char, Traits, Allocator> type; }; template<class Char, class Traits, class Allocator, std::size_t N> struct plain_return_type_2<arithmetic_action<plus_action>, Char[N], std::basic_string<Char, Traits, Allocator> > { typedef std::basic_string<Char, Traits, Allocator> type; }; template<class Char, class Traits, class Allocator, std::size_t N> struct plain_return_type_2<arithmetic_action<plus_action>, std::basic_string<Char, Traits, Allocator>, Char[N]> { typedef std::basic_string<Char, Traits, Allocator> type; }; } // namespace lambda } // namespace boost #endif