/*=============================================================================
|
Copyright (c) 2016 Paul Fultz II
|
limit.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_LIMIT_H
|
#define BOOST_HOF_GUARD_LIMIT_H
|
|
/// limit
|
/// =====
|
///
|
/// Description
|
/// -----------
|
///
|
/// The `limit` function decorator annotates the function with the max number
|
/// of parameters. The `limit_c` version can be used to give the max number
|
/// directly(instead of relying on an integral constant). The parameter limit
|
/// can be read by using the [`function_param_limit`](function_param_limit)
|
/// trait. Using `limit` is useful to improve error reporting with partially
|
/// evaluated functions.
|
///
|
/// Synopsis
|
/// --------
|
///
|
/// template<class IntegralConstant>
|
/// constexpr auto limit(IntegralConstant);
|
///
|
/// template<std::size_t N, class F>
|
/// constexpr auto limit_c(F);
|
///
|
/// Requirements
|
/// ------------
|
///
|
/// IntegralConstant must be:
|
///
|
/// * IntegralConstant
|
///
|
/// F must be:
|
///
|
/// * [ConstInvocable](ConstInvocable)
|
/// * MoveConstructible
|
///
|
/// Example
|
/// -------
|
///
|
/// #include <boost/hof.hpp>
|
/// #include <cassert>
|
/// using namespace boost::hof;
|
///
|
/// struct sum_f
|
/// {
|
/// template<class T>
|
/// int operator()(T x, T y) const
|
/// {
|
/// return x+y;
|
/// }
|
/// };
|
/// BOOST_HOF_STATIC_FUNCTION(sum) = limit_c<2>(sum_f());
|
///
|
/// int main() {
|
/// assert(3 == sum(1, 2));
|
/// }
|
///
|
/// See Also
|
/// --------
|
///
|
/// * [Partial function evaluation](<Partial function evaluation>)
|
/// * [function_param_limit](function_param_limit)
|
///
|
|
#include <boost/hof/detail/callable_base.hpp>
|
#include <boost/hof/detail/forward.hpp>
|
#include <boost/hof/detail/delegate.hpp>
|
#include <boost/hof/detail/move.hpp>
|
#include <boost/hof/detail/static_const_var.hpp>
|
#include <boost/hof/always.hpp>
|
#include <boost/hof/function_param_limit.hpp>
|
|
namespace boost { namespace hof {
|
|
namespace detail {
|
// TODO: Make this work with fit_rewritable1_tag
|
template<std::size_t N, class F>
|
struct limit_adaptor : detail::callable_base<F>
|
{
|
typedef std::integral_constant<std::size_t, N> fit_function_param_limit;
|
BOOST_HOF_INHERIT_CONSTRUCTOR(limit_adaptor, detail::callable_base<F>)
|
|
template<class... Ts>
|
constexpr const detail::callable_base<F>& base_function(Ts&&... xs) const
|
{
|
return boost::hof::always_ref(*this)(xs...);
|
}
|
|
BOOST_HOF_RETURNS_CLASS(limit_adaptor);
|
|
template<class... Ts, class=typename std::enable_if<(sizeof...(Ts) <= N)>::type>
|
constexpr BOOST_HOF_SFINAE_RESULT(const detail::callable_base<F>&, id_<Ts>...)
|
operator()(Ts&&... xs) const BOOST_HOF_SFINAE_RETURNS
|
(
|
(BOOST_HOF_MANGLE_CAST(const detail::callable_base<F>&)(BOOST_HOF_CONST_THIS->base_function(xs...)))
|
(BOOST_HOF_FORWARD(Ts)(xs)...)
|
);
|
|
};
|
|
template<std::size_t N>
|
struct make_limit_f
|
{
|
constexpr make_limit_f()
|
{}
|
template<class F>
|
constexpr limit_adaptor<N, F> operator()(F f) const
|
{
|
return limit_adaptor<N, F>(static_cast<F&&>(f));
|
}
|
};
|
|
struct limit_f
|
{
|
template<class IntegralConstant, std::size_t N=IntegralConstant::type::value>
|
constexpr make_limit_f<N> operator()(IntegralConstant) const
|
{
|
return {};
|
}
|
};
|
|
}
|
|
template<std::size_t N, class F>
|
constexpr detail::limit_adaptor<N, F> limit_c(F f)
|
{
|
return detail::limit_adaptor<N, F>(static_cast<F&&>(f));
|
}
|
|
BOOST_HOF_DECLARE_STATIC_VAR(limit, detail::limit_f);
|
|
}} // namespace boost::hof
|
|
#endif
|
