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