mirror of
https://github.com/PurpleI2P/Boost-for-Android-Prebuilt
synced 2025-01-08 22:08:01 +00:00
266 lines
7.3 KiB
C++
266 lines
7.3 KiB
C++
/*=============================================================================
|
|
Copyright (c) 2014 Paul Fultz II
|
|
proj.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_FUNCTION_ON_H
|
|
#define BOOST_HOF_GUARD_FUNCTION_ON_H
|
|
|
|
/// proj
|
|
/// ====
|
|
///
|
|
/// Description
|
|
/// -----------
|
|
///
|
|
/// The `proj` function adaptor applies a projection onto the parameters of
|
|
/// another function. This is useful, for example, to define a function for
|
|
/// sorting such that the ordering is based off of the value of one of its
|
|
/// member fields.
|
|
///
|
|
/// Also, if just a projection is given, then the projection will be called
|
|
/// for each of its arguments.
|
|
///
|
|
/// Note: All projections are always evaluated in order from left-to-right.
|
|
///
|
|
/// Synopsis
|
|
/// --------
|
|
///
|
|
/// template<class Projection, class F>
|
|
/// constexpr proj_adaptor<Projection, F> proj(Projection p, F f);
|
|
///
|
|
/// template<class Projection>
|
|
/// constexpr proj_adaptor<Projection> proj(Projection p);
|
|
///
|
|
/// Semantics
|
|
/// ---------
|
|
///
|
|
/// assert(proj(p, f)(xs...) == f(p(xs)...));
|
|
/// assert(proj(p)(xs...) == p(xs)...);
|
|
///
|
|
/// Requirements
|
|
/// ------------
|
|
///
|
|
/// Projection must be:
|
|
///
|
|
/// * [UnaryInvocable](UnaryInvocable)
|
|
/// * MoveConstructible
|
|
///
|
|
/// F must be:
|
|
///
|
|
/// * [ConstInvocable](ConstInvocable)
|
|
/// * MoveConstructible
|
|
///
|
|
/// Example
|
|
/// -------
|
|
///
|
|
/// #include <boost/hof.hpp>
|
|
/// #include <cassert>
|
|
/// using namespace boost::hof;
|
|
///
|
|
/// struct foo
|
|
/// {
|
|
/// foo(int x_) : x(x_)
|
|
/// {}
|
|
/// int x;
|
|
/// };
|
|
///
|
|
/// int main() {
|
|
/// assert(boost::hof::proj(&foo::x, _ + _)(foo(1), foo(2)) == 3);
|
|
/// }
|
|
///
|
|
/// References
|
|
/// ----------
|
|
///
|
|
/// * [Projections](Projections)
|
|
/// * [Variadic print](<Variadic print>)
|
|
///
|
|
|
|
|
|
|
|
#include <utility>
|
|
#include <boost/hof/always.hpp>
|
|
#include <boost/hof/detail/callable_base.hpp>
|
|
#include <boost/hof/detail/result_of.hpp>
|
|
#include <boost/hof/detail/move.hpp>
|
|
#include <boost/hof/detail/make.hpp>
|
|
#include <boost/hof/detail/static_const_var.hpp>
|
|
#include <boost/hof/detail/compressed_pair.hpp>
|
|
#include <boost/hof/detail/result_type.hpp>
|
|
#include <boost/hof/apply_eval.hpp>
|
|
|
|
namespace boost { namespace hof {
|
|
|
|
namespace detail {
|
|
|
|
template<class T, class Projection>
|
|
struct project_eval
|
|
{
|
|
T&& x;
|
|
const Projection& p;
|
|
|
|
template<class X, class P>
|
|
constexpr project_eval(X&& xp, const P& pp) : x(BOOST_HOF_FORWARD(X)(xp)), p(pp)
|
|
{}
|
|
|
|
constexpr auto operator()() const BOOST_HOF_RETURNS
|
|
(p(BOOST_HOF_FORWARD(T)(x)));
|
|
};
|
|
|
|
template<class T, class Projection>
|
|
constexpr project_eval<T, Projection> make_project_eval(T&& x, const Projection& p)
|
|
{
|
|
return project_eval<T, Projection>(BOOST_HOF_FORWARD(T)(x), p);
|
|
}
|
|
|
|
template<class T, class Projection>
|
|
struct project_void_eval
|
|
{
|
|
T&& x;
|
|
const Projection& p;
|
|
|
|
template<class X, class P>
|
|
constexpr project_void_eval(X&& xp, const P& pp) : x(BOOST_HOF_FORWARD(X)(xp)), p(pp)
|
|
{}
|
|
|
|
struct void_ {};
|
|
|
|
constexpr void_ operator()() const
|
|
{
|
|
return p(BOOST_HOF_FORWARD(T)(x)), void_();
|
|
}
|
|
};
|
|
|
|
template<class T, class Projection>
|
|
constexpr project_void_eval<T, Projection> make_project_void_eval(T&& x, const Projection& p)
|
|
{
|
|
return project_void_eval<T, Projection>(BOOST_HOF_FORWARD(T)(x), p);
|
|
}
|
|
|
|
template<class Projection, class F, class... Ts,
|
|
class R=decltype(
|
|
std::declval<const F&>()(std::declval<const Projection&>()(std::declval<Ts>())...)
|
|
)>
|
|
constexpr R by_eval(const Projection& p, const F& f, Ts&&... xs)
|
|
{
|
|
return boost::hof::apply_eval(f, make_project_eval(BOOST_HOF_FORWARD(Ts)(xs), p)...);
|
|
}
|
|
|
|
#if BOOST_HOF_NO_ORDERED_BRACE_INIT
|
|
#define BOOST_HOF_BY_VOID_RETURN BOOST_HOF_ALWAYS_VOID_RETURN
|
|
#else
|
|
#if BOOST_HOF_NO_CONSTEXPR_VOID
|
|
#define BOOST_HOF_BY_VOID_RETURN boost::hof::detail::swallow
|
|
#else
|
|
#define BOOST_HOF_BY_VOID_RETURN void
|
|
#endif
|
|
#endif
|
|
|
|
template<class Projection, class... Ts>
|
|
constexpr BOOST_HOF_ALWAYS_VOID_RETURN by_void_eval(const Projection& p, Ts&&... xs)
|
|
{
|
|
return boost::hof::apply_eval(boost::hof::always(), boost::hof::detail::make_project_void_eval(BOOST_HOF_FORWARD(Ts)(xs), p)...);
|
|
}
|
|
|
|
struct swallow
|
|
{
|
|
template<class... Ts>
|
|
constexpr swallow(Ts&&...)
|
|
{}
|
|
};
|
|
|
|
}
|
|
|
|
template<class Projection, class F=void>
|
|
struct proj_adaptor;
|
|
|
|
template<class Projection, class F>
|
|
struct proj_adaptor : detail::compressed_pair<detail::callable_base<Projection>, detail::callable_base<F>>, detail::function_result_type<F>
|
|
{
|
|
typedef proj_adaptor fit_rewritable_tag;
|
|
typedef detail::compressed_pair<detail::callable_base<Projection>, detail::callable_base<F>> base;
|
|
template<class... Ts>
|
|
constexpr const detail::callable_base<F>& base_function(Ts&&... xs) const
|
|
{
|
|
return this->second(xs...);;
|
|
}
|
|
|
|
template<class... Ts>
|
|
constexpr const detail::callable_base<Projection>& base_projection(Ts&&... xs) const
|
|
{
|
|
return this->first(xs...);
|
|
}
|
|
|
|
struct by_failure
|
|
{
|
|
template<class Failure>
|
|
struct apply
|
|
{
|
|
template<class... Ts>
|
|
struct of
|
|
: Failure::template of<decltype(std::declval<detail::callable_base<Projection>>()(std::declval<Ts>()))...>
|
|
{};
|
|
};
|
|
};
|
|
|
|
struct failure
|
|
: failure_map<by_failure, detail::callable_base<F>>
|
|
{};
|
|
|
|
BOOST_HOF_INHERIT_CONSTRUCTOR(proj_adaptor, base)
|
|
|
|
BOOST_HOF_RETURNS_CLASS(proj_adaptor);
|
|
|
|
template<class... Ts>
|
|
constexpr BOOST_HOF_SFINAE_RESULT(const detail::callable_base<F>&, result_of<const detail::callable_base<Projection>&, id_<Ts>>...)
|
|
operator()(Ts&&... xs) const BOOST_HOF_SFINAE_RETURNS
|
|
(
|
|
boost::hof::detail::by_eval(
|
|
BOOST_HOF_MANGLE_CAST(const detail::callable_base<Projection>&)(BOOST_HOF_CONST_THIS->base_projection(xs...)),
|
|
BOOST_HOF_MANGLE_CAST(const detail::callable_base<F>&)(BOOST_HOF_CONST_THIS->base_function(xs...)),
|
|
BOOST_HOF_FORWARD(Ts)(xs)...
|
|
)
|
|
);
|
|
};
|
|
|
|
template<class Projection>
|
|
struct proj_adaptor<Projection, void> : detail::callable_base<Projection>
|
|
{
|
|
typedef proj_adaptor fit_rewritable1_tag;
|
|
template<class... Ts>
|
|
constexpr const detail::callable_base<Projection>& base_projection(Ts&&... xs) const
|
|
{
|
|
return boost::hof::always_ref(*this)(xs...);
|
|
}
|
|
|
|
BOOST_HOF_INHERIT_DEFAULT(proj_adaptor, detail::callable_base<Projection>)
|
|
|
|
template<class P, BOOST_HOF_ENABLE_IF_CONVERTIBLE(P, detail::callable_base<Projection>)>
|
|
constexpr proj_adaptor(P&& p)
|
|
: detail::callable_base<Projection>(BOOST_HOF_FORWARD(P)(p))
|
|
{}
|
|
|
|
BOOST_HOF_RETURNS_CLASS(proj_adaptor);
|
|
|
|
template<class... Ts, class=detail::holder<decltype(std::declval<Projection>()(std::declval<Ts>()))...>>
|
|
constexpr BOOST_HOF_BY_VOID_RETURN operator()(Ts&&... xs) const
|
|
{
|
|
#if BOOST_HOF_NO_ORDERED_BRACE_INIT
|
|
return boost::hof::detail::by_void_eval(this->base_projection(xs...), BOOST_HOF_FORWARD(Ts)(xs)...);
|
|
#else
|
|
#if BOOST_HOF_NO_CONSTEXPR_VOID
|
|
return
|
|
#endif
|
|
boost::hof::detail::swallow{
|
|
(this->base_projection(xs...)(BOOST_HOF_FORWARD(Ts)(xs)), 0)...
|
|
};
|
|
#endif
|
|
}
|
|
};
|
|
|
|
BOOST_HOF_DECLARE_STATIC_VAR(proj, detail::make<proj_adaptor>);
|
|
|
|
}} // namespace boost::hof
|
|
#endif
|