115 lines
3.7 KiB
C++
115 lines
3.7 KiB
C++
|
/*!
|
||
|
|
@file
|
||
|
|
Defines `boost::hana::lockstep`.
|
||
|
|
|
||
|
|
@copyright Louis Dionne 2013-2016
|
||
|
|
Distributed under the Boost Software License, Version 1.0.
|
||
|
|
(See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
|
||
|
|
*/
|
||
|
|
|
||
|
|
#ifndef BOOST_HANA_FUNCTIONAL_LOCKSTEP_HPP
|
||
|
|
#define BOOST_HANA_FUNCTIONAL_LOCKSTEP_HPP
|
||
|
|
|
||
|
|
#include <boost/hana/basic_tuple.hpp>
|
||
|
|
#include <boost/hana/config.hpp>
|
||
|
|
#include <boost/hana/detail/decay.hpp>
|
||
|
|
|
||
|
|
#include <cstddef>
|
||
|
|
#include <utility>
|
||
|
|
|
||
|
|
|
||
|
|
BOOST_HANA_NAMESPACE_BEGIN
|
||
|
|
//! @ingroup group-functional
|
||
|
|
//! Invoke a function with the result of invoking other functions on its
|
||
|
|
//! arguments, in lockstep.
|
||
|
|
//!
|
||
|
|
//! Specifically, `lockstep(f)(g1, ..., gN)` is a function such that
|
||
|
|
//! @code
|
||
|
|
//! lockstep(f)(g1, ..., gN)(x1, ..., xN) == f(g1(x1), ..., gN(xN))
|
||
|
|
//! @endcode
|
||
|
|
//!
|
||
|
|
//! Since each `g` is invoked on its corresponding argument in lockstep,
|
||
|
|
//! the number of arguments must match the number of `g`s.
|
||
|
|
//!
|
||
|
|
//!
|
||
|
|
//! Example
|
||
|
|
//! -------
|
||
|
|
//! @include example/functional/lockstep.cpp
|
||
|
|
#ifdef BOOST_HANA_DOXYGEN_INVOKED
|
||
|
|
constexpr auto lockstep = [](auto&& f, auto&& ...g) {
|
||
|
|
return [perfect-capture](auto&& ...x) -> decltype(auto) {
|
||
|
|
return forwarded(f)(forwarded(g)(forwarded(x))...);
|
||
|
|
};
|
||
|
|
};
|
||
|
|
#else
|
||
|
|
template <typename Indices, typename F, typename ...G>
|
||
|
|
struct lockstep_t;
|
||
|
|
|
||
|
|
template <typename F>
|
||
|
|
struct pre_lockstep_t;
|
||
|
|
|
||
|
|
struct make_pre_lockstep_t {
|
||
|
|
struct secret { };
|
||
|
|
template <typename F>
|
||
|
|
constexpr pre_lockstep_t<typename detail::decay<F>::type> operator()(F&& f) const {
|
||
|
|
return {static_cast<F&&>(f)};
|
||
|
|
}
|
||
|
|
};
|
||
|
|
|
||
|
|
template <std::size_t ...n, typename F, typename ...G>
|
||
|
|
struct lockstep_t<std::index_sequence<n...>, F, G...> {
|
||
|
|
template <typename ...T>
|
||
|
|
constexpr lockstep_t(make_pre_lockstep_t::secret, T&& ...t)
|
||
|
|
: storage_{static_cast<T&&>(t)...}
|
||
|
|
{ }
|
||
|
|
|
||
|
|
basic_tuple<F, G...> storage_;
|
||
|
|
|
||
|
|
template <typename ...X>
|
||
|
|
constexpr decltype(auto) operator()(X&& ...x) const& {
|
||
|
|
return hana::get_impl<0>(storage_)(
|
||
|
|
hana::get_impl<n+1>(storage_)(static_cast<X&&>(x))...
|
||
|
|
);
|
||
|
|
}
|
||
|
|
|
||
|
|
template <typename ...X>
|
||
|
|
constexpr decltype(auto) operator()(X&& ...x) & {
|
||
|
|
return hana::get_impl<0>(storage_)(
|
||
|
|
hana::get_impl<n+1>(storage_)(static_cast<X&&>(x))...
|
||
|
|
);
|
||
|
|
}
|
||
|
|
|
||
|
|
template <typename ...X>
|
||
|
|
constexpr decltype(auto) operator()(X&& ...x) && {
|
||
|
|
return static_cast<F&&>(hana::get_impl<0>(storage_))(
|
||
|
|
static_cast<G&&>(hana::get_impl<n+1>(storage_))(static_cast<X&&>(x))...
|
||
|
|
);
|
||
|
|
}
|
||
|
|
};
|
||
|
|
|
||
|
|
template <typename F>
|
||
|
|
struct pre_lockstep_t {
|
||
|
|
F f;
|
||
|
|
|
||
|
|
template <typename ...G>
|
||
|
|
constexpr lockstep_t<std::make_index_sequence<sizeof...(G)>, F,
|
||
|
|
typename detail::decay<G>::type...>
|
||
|
|
operator()(G&& ...g) const& {
|
||
|
|
return {make_pre_lockstep_t::secret{}, this->f, static_cast<G&&>(g)...};
|
||
|
|
}
|
||
|
|
|
||
|
|
template <typename ...G>
|
||
|
|
constexpr lockstep_t<std::make_index_sequence<sizeof...(G)>, F,
|
||
|
|
typename detail::decay<G>::type...>
|
||
|
|
operator()(G&& ...g) && {
|
||
|
|
return {make_pre_lockstep_t::secret{}, static_cast<F&&>(this->f),
|
||
|
|
static_cast<G&&>(g)...};
|
||
|
|
}
|
||
|
|
};
|
||
|
|
|
||
|
|
constexpr make_pre_lockstep_t lockstep{};
|
||
|
|
#endif
|
||
|
|
BOOST_HANA_NAMESPACE_END
|
||
|
|
|
||
|
|
#endif // !BOOST_HANA_FUNCTIONAL_LOCKSTEP_HPP
|