/usr/include/boost/hana/functional
Edit: /usr/include/boost/hana/functional/lockstep.hpp (3610B)
/*!
@file
Defines `boost::hana::lockstep`.
@copyright Louis Dionne 2013-2017
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
#include
#include
#include
#include
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
struct lockstep_t;
template
struct pre_lockstep_t;
struct make_pre_lockstep_t {
struct secret { };
template
constexpr pre_lockstep_t::type> operator()(F&& f) const {
return {static_cast(f)};
}
};
template
struct lockstep_t, F, G...> {
template
constexpr lockstep_t(make_pre_lockstep_t::secret, T&& ...t)
: storage_{static_cast(t)...}
{ }
basic_tuple storage_;
template
constexpr decltype(auto) operator()(X&& ...x) const& {
return hana::at_c<0>(storage_)(
hana::at_c(storage_)(static_cast(x))...
);
}
template
constexpr decltype(auto) operator()(X&& ...x) & {
return hana::at_c<0>(storage_)(
hana::at_c(storage_)(static_cast(x))...
);
}
template
constexpr decltype(auto) operator()(X&& ...x) && {
return static_cast(hana::at_c<0>(storage_))(
static_cast(hana::at_c(storage_))(static_cast(x))...
);
}
};
template
struct pre_lockstep_t {
F f;
template
constexpr lockstep_t, F,
typename detail::decay::type...>
operator()(G&& ...g) const& {
return {make_pre_lockstep_t::secret{}, this->f, static_cast(g)...};
}
template
constexpr lockstep_t, F,
typename detail::decay::type...>
operator()(G&& ...g) && {
return {make_pre_lockstep_t::secret{}, static_cast(this->f),
static_cast(g)...};
}
};
constexpr make_pre_lockstep_t lockstep{};
#endif
BOOST_HANA_NAMESPACE_END
#endif // !BOOST_HANA_FUNCTIONAL_LOCKSTEP_HPP