Edit: /usr/include/boost/hof/returns.hpp (8607B)
/*=============================================================================
Copyright (c) 2014 Paul Fultz II
returns.h
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)
==============================================================================*/
#ifndef BOOST_HOF_GUARD_RETURNS_H
#define BOOST_HOF_GUARD_RETURNS_H
/// BOOST_HOF_RETURNS
/// ===========
///
/// Description
/// -----------
///
/// The `BOOST_HOF_RETURNS` macro defines the function as the expression
/// equivalence. It does this by deducing `noexcept` and the return type by
/// using a trailing `decltype`. Instead of repeating the expression for the
/// return type, `noexcept` clause and the function body, this macro will
/// reduce the code duplication from that.
///
/// Note: The expression used to deduce the return the type will also
/// constrain the template function and deduce `noexcept` as well, which is
/// different behaviour than using C++14's return type deduction.
///
/// Synopsis
/// --------
///
/// #define BOOST_HOF_RETURNS(...)
///
///
/// Example
/// -------
///
/// #include
/// #include
///
/// template
/// auto sum(T x, U y) BOOST_HOF_RETURNS(x+y);
///
/// int main() {
/// assert(3 == sum(1, 2));
/// }
///
///
/// Incomplete this
/// ---------------
///
/// Description
/// -----------
///
/// On some non-conformant compilers, such as gcc, the `this` variable cannot
/// be used inside the `BOOST_HOF_RETURNS` macro because it is considered an
/// incomplete type. So the following macros are provided to help workaround
/// the issue.
///
///
/// Synopsis
/// --------
///
/// // Declares the type of the `this` variable
/// #define BOOST_HOF_RETURNS_CLASS(...)
/// // Used to refer to the `this` variable in the BOOST_HOF_RETURNS macro
/// #define BOOST_HOF_THIS
/// // Used to refer to the const `this` variable in the BOOST_HOF_RETURNS macro
/// #define BOOST_HOF_CONST_THIS
///
///
/// Example
/// -------
///
/// #include
/// #include
///
/// struct add_1
/// {
/// int a;
/// add_1() : a(1) {}
///
/// BOOST_HOF_RETURNS_CLASS(add_1);
///
/// template
/// auto operator()(T x) const
/// BOOST_HOF_RETURNS(x+BOOST_HOF_CONST_THIS->a);
/// };
///
/// int main() {
/// assert(3 == add_1()(2));
/// }
///
///
/// Mangling overloads
/// ------------------
///
/// Description
/// -----------
///
/// On older compilers some operations done in the expressions cannot be
/// properly mangled. These macros help provide workarounds for these
/// operations on older compilers.
///
///
/// Synopsis
/// --------
///
/// // Explicitly defines the type for name mangling
/// #define BOOST_HOF_MANGLE_CAST(...)
/// // C cast for name mangling
/// #define BOOST_HOF_RETURNS_C_CAST(...)
/// // Reinterpret cast for name mangling
/// #define BOOST_HOF_RETURNS_REINTERPRET_CAST(...)
/// // Static cast for name mangling
/// #define BOOST_HOF_RETURNS_STATIC_CAST(...)
/// // Construction for name mangling
/// #define BOOST_HOF_RETURNS_CONSTRUCT(...)
///
#include
#include
#include
#include
#define BOOST_HOF_EAT(...)
#define BOOST_HOF_REM(...) __VA_ARGS__
#if BOOST_HOF_HAS_COMPLETE_DECLTYPE && BOOST_HOF_HAS_MANGLE_OVERLOAD
#ifdef _MSC_VER
// Since decltype can't be used in noexcept on MSVC, we can't check for noexcept
// move constructors.
#define BOOST_HOF_RETURNS_DEDUCE_NOEXCEPT(...) BOOST_HOF_NOEXCEPT(noexcept(__VA_ARGS__))
#else
#define BOOST_HOF_RETURNS_DEDUCE_NOEXCEPT(...) BOOST_HOF_NOEXCEPT(noexcept(static_cast(__VA_ARGS__)))
#endif
#define BOOST_HOF_RETURNS(...) \
BOOST_HOF_RETURNS_DEDUCE_NOEXCEPT(__VA_ARGS__) \
-> decltype(__VA_ARGS__) { return __VA_ARGS__; }
#define BOOST_HOF_THIS this
#define BOOST_HOF_CONST_THIS this
#define BOOST_HOF_RETURNS_CLASS(...) \
void fit_returns_class_check() \
{ \
static_assert(std::is_same<__VA_ARGS__*, decltype(this)>::value, \
"Returns class " #__VA_ARGS__ " type doesn't match"); \
}
#define BOOST_HOF_MANGLE_CAST(...) BOOST_HOF_REM
#define BOOST_HOF_RETURNS_C_CAST(...) (__VA_ARGS__) BOOST_HOF_REM
#define BOOST_HOF_RETURNS_REINTERPRET_CAST(...) reinterpret_cast<__VA_ARGS__>
#define BOOST_HOF_RETURNS_STATIC_CAST(...) static_cast<__VA_ARGS__>
#define BOOST_HOF_RETURNS_CONSTRUCT(...) __VA_ARGS__
#else
#include
#define BOOST_HOF_RETURNS_RETURN(...) return BOOST_HOF_RETURNS_RETURN_X(BOOST_HOF_PP_WALL(__VA_ARGS__))
#define BOOST_HOF_RETURNS_RETURN_X(...) __VA_ARGS__
#ifdef _MSC_VER
// Since decltype can't be used in noexcept on MSVC, we can't check for noexcept
// move constructors.
#define BOOST_HOF_RETURNS_DEDUCE_NOEXCEPT(...) BOOST_HOF_NOEXCEPT(noexcept(BOOST_HOF_RETURNS_DECLTYPE_CONTEXT(__VA_ARGS__)))
#else
#define BOOST_HOF_RETURNS_DEDUCE_NOEXCEPT(...) BOOST_HOF_NOEXCEPT(noexcept(static_cast(BOOST_HOF_RETURNS_DECLTYPE_CONTEXT(__VA_ARGS__))))
#endif
#define BOOST_HOF_RETURNS_DECLTYPE(...) \
-> decltype(BOOST_HOF_RETURNS_DECLTYPE_CONTEXT(__VA_ARGS__))
#define BOOST_HOF_RETURNS_DECLTYPE_CONTEXT(...) BOOST_HOF_RETURNS_DECLTYPE_CONTEXT_X(BOOST_HOF_PP_WALL(__VA_ARGS__))
#define BOOST_HOF_RETURNS_DECLTYPE_CONTEXT_X(...) __VA_ARGS__
#define BOOST_HOF_RETURNS_THAT(...) BOOST_HOF_PP_IIF(BOOST_HOF_PP_IS_PAREN(BOOST_HOF_RETURNS_DECLTYPE_CONTEXT(())))(\
(boost::hof::detail::check_this<__VA_ARGS__, decltype(this)>(), this), \
std::declval<__VA_ARGS__>() \
)
#define BOOST_HOF_THIS BOOST_HOF_PP_RAIL(BOOST_HOF_RETURNS_THAT)(fit_this_type)
#define BOOST_HOF_CONST_THIS BOOST_HOF_PP_RAIL(BOOST_HOF_RETURNS_THAT)(fit_const_this_type)
#define BOOST_HOF_RETURNS_CLASS(...) typedef __VA_ARGS__* fit_this_type; typedef const __VA_ARGS__* fit_const_this_type
#define BOOST_HOF_RETURNS(...) \
BOOST_HOF_RETURNS_DEDUCE_NOEXCEPT(__VA_ARGS__) \
BOOST_HOF_RETURNS_DECLTYPE(__VA_ARGS__) \
{ BOOST_HOF_RETURNS_RETURN(__VA_ARGS__); }
namespace boost { namespace hof { namespace detail {
template
struct check_this
{
static_assert(std::is_same::value, "Incorret BOOST_HOF_THIS or BOOST_HOF_CONST_THIS used.");
};
}}} // namespace boost::hof
#endif
#if BOOST_HOF_HAS_MANGLE_OVERLOAD
#define BOOST_HOF_MANGLE_CAST(...) BOOST_HOF_REM
#define BOOST_HOF_RETURNS_C_CAST(...) (__VA_ARGS__) BOOST_HOF_REM
#define BOOST_HOF_RETURNS_REINTERPRET_CAST(...) reinterpret_cast<__VA_ARGS__>
#define BOOST_HOF_RETURNS_STATIC_CAST(...) static_cast<__VA_ARGS__>
#define BOOST_HOF_RETURNS_CONSTRUCT(...) __VA_ARGS__
#else
#define BOOST_HOF_RETURNS_DERAIL_MANGLE_CAST(...) BOOST_HOF_PP_IIF(BOOST_HOF_PP_IS_PAREN(BOOST_HOF_RETURNS_DECLTYPE_CONTEXT(())))(\
BOOST_HOF_REM, \
std::declval<__VA_ARGS__>() BOOST_HOF_EAT \
)
#define BOOST_HOF_MANGLE_CAST BOOST_HOF_PP_RAIL(BOOST_HOF_RETURNS_DERAIL_MANGLE_CAST)
#define BOOST_HOF_RETURNS_DERAIL_C_CAST(...) BOOST_HOF_PP_IIF(BOOST_HOF_PP_IS_PAREN(BOOST_HOF_RETURNS_DECLTYPE_CONTEXT(())))(\
(__VA_ARGS__) BOOST_HOF_REM, \
std::declval<__VA_ARGS__>() BOOST_HOF_EAT \
)
#define BOOST_HOF_RETURNS_C_CAST BOOST_HOF_PP_RAIL(BOOST_HOF_RETURNS_DERAIL_C_CAST)
#define BOOST_HOF_RETURNS_DERAIL_REINTERPRET_CAST(...) BOOST_HOF_PP_IIF(BOOST_HOF_PP_IS_PAREN(BOOST_HOF_RETURNS_DECLTYPE_CONTEXT(())))(\
reinterpret_cast<__VA_ARGS__>, \
std::declval<__VA_ARGS__>() BOOST_HOF_EAT \
)
#define BOOST_HOF_RETURNS_REINTERPRET_CAST BOOST_HOF_PP_RAIL(BOOST_HOF_RETURNS_DERAIL_REINTERPRET_CAST)
#define BOOST_HOF_RETURNS_DERAIL_STATIC_CAST(...) BOOST_HOF_PP_IIF(BOOST_HOF_PP_IS_PAREN(BOOST_HOF_RETURNS_DECLTYPE_CONTEXT(())))(\
static_cast<__VA_ARGS__>, \
std::declval<__VA_ARGS__>() BOOST_HOF_EAT \
)
#define BOOST_HOF_RETURNS_STATIC_CAST BOOST_HOF_PP_RAIL(BOOST_HOF_RETURNS_DERAIL_STATIC_CAST)
#define BOOST_HOF_RETURNS_DERAIL_CONSTRUCT(...) BOOST_HOF_PP_IIF(BOOST_HOF_PP_IS_PAREN(BOOST_HOF_RETURNS_DECLTYPE_CONTEXT(())))(\
__VA_ARGS__, \
std::declval<__VA_ARGS__>() BOOST_HOF_EAT \
)
#define BOOST_HOF_RETURNS_CONSTRUCT BOOST_HOF_PP_RAIL(BOOST_HOF_RETURNS_DERAIL_CONSTRUCT)
#endif
#define BOOST_HOF_AUTO_FORWARD(...) BOOST_HOF_RETURNS_STATIC_CAST(decltype(__VA_ARGS__))(__VA_ARGS__)
#endif