Edit: /usr/include/boost/hof/result.hpp (3644B)
/*=============================================================================
Copyright (c) 2014 Paul Fultz II
result.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_RESULT_H
#define BOOST_HOF_GUARD_RESULT_H
/// result
/// ======
///
/// Description
/// -----------
///
/// The `result` function adaptor sets the return type for the function, which
/// can be useful when dealing with multiple overloads. Since the return type
/// is no longer dependent on the parameters passed to the function, the
/// `result_adaptor` provides a nested `result_type` that is the return type
/// of the function.
///
/// Synopsis
/// --------
///
/// template
/// constexpr result_adaptor result(F f);
///
/// Requirements
/// ------------
///
/// F must be:
///
/// * [ConstInvocable](ConstInvocable)
/// * MoveConstructible
///
/// Example
/// -------
///
/// #include
/// #include
///
/// struct id
/// {
/// template
/// T operator()(T x) const
/// {
/// return x;
/// }
/// };
///
/// int main() {
/// auto int_result = boost::hof::result(id());
/// static_assert(std::is_same::value, "Not the same type");
/// }
///
#include
#include
#include
#include
namespace boost { namespace hof {
template
struct result_adaptor : detail::callable_base
{
BOOST_HOF_INHERIT_CONSTRUCTOR(result_adaptor, detail::callable_base)
typedef Result result_type;
struct failure
: failure_for>
{};
template
constexpr const detail::callable_base& base_function(Ts&&... xs) const
{
return boost::hof::always_ref(*this)(xs...);
}
template::value)>::type>
constexpr result_type operator()(Ts&&... xs) const
{
return this->base_function(xs...)(BOOST_HOF_FORWARD(Ts)(xs)...);
};
};
template
struct result_adaptor : detail::callable_base
{
BOOST_HOF_INHERIT_CONSTRUCTOR(result_adaptor, detail::callable_base)
typedef void result_type;
template
constexpr const detail::callable_base& base_function(Ts&&... xs) const
{
return boost::hof::always_ref(*this)(xs...);
}
template::value)>::type>
constexpr typename detail::holder::type operator()(Ts&&... xs) const
{
return (typename detail::holder::type)this->base_function(xs...)(BOOST_HOF_FORWARD(Ts)(xs)...);
};
};
#if BOOST_HOF_HAS_VARIABLE_TEMPLATES
namespace result_detail {
template
struct result_f
{
template
constexpr result_adaptor operator()(F f) const
{
return result_adaptor(boost::hof::move(f));
}
};
}
template
static constexpr auto result = result_detail::result_f{};
#else
template
constexpr result_adaptor result(F f)
{
return result_adaptor(boost::hof::move(f));
}
#endif
}} // namespace boost::hof
#endif