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142 lines
3.7 KiB
142 lines
3.7 KiB
/*============================================================================= |
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Copyright (c) 2016 Paul Fultz II |
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limit.h |
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Distributed under the Boost Software License, Version 1.0. (See accompanying |
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file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) |
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==============================================================================*/ |
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#ifndef BOOST_HOF_GUARD_LIMIT_H |
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#define BOOST_HOF_GUARD_LIMIT_H |
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/// limit |
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/// ===== |
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/// |
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/// Description |
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/// ----------- |
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/// |
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/// The `limit` function decorator annotates the function with the max number |
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/// of parameters. The `limit_c` version can be used to give the max number |
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/// directly(instead of relying on an integral constant). The parameter limit |
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/// can be read by using the [`function_param_limit`](function_param_limit) |
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/// trait. Using `limit` is useful to improve error reporting with partially |
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/// evaluated functions. |
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/// |
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/// Synopsis |
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/// -------- |
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/// |
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/// template<class IntegralConstant> |
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/// constexpr auto limit(IntegralConstant); |
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/// |
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/// template<std::size_t N, class F> |
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/// constexpr auto limit_c(F); |
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/// |
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/// Requirements |
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/// ------------ |
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/// |
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/// IntegralConstant must be: |
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/// |
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/// * IntegralConstant |
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/// |
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/// F must be: |
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/// |
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/// * [ConstInvocable](ConstInvocable) |
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/// * MoveConstructible |
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/// |
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/// Example |
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/// ------- |
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/// |
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/// #include <boost/hof.hpp> |
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/// #include <cassert> |
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/// using namespace boost::hof; |
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/// |
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/// struct sum_f |
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/// { |
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/// template<class T> |
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/// int operator()(T x, T y) const |
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/// { |
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/// return x+y; |
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/// } |
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/// }; |
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/// BOOST_HOF_STATIC_FUNCTION(sum) = limit_c<2>(sum_f()); |
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/// |
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/// int main() { |
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/// assert(3 == sum(1, 2)); |
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/// } |
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/// |
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/// See Also |
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/// -------- |
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/// |
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/// * [Partial function evaluation](<Partial function evaluation>) |
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/// * [function_param_limit](function_param_limit) |
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/// |
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#include <boost/hof/detail/callable_base.hpp> |
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#include <boost/hof/detail/forward.hpp> |
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#include <boost/hof/detail/delegate.hpp> |
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#include <boost/hof/detail/move.hpp> |
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#include <boost/hof/detail/static_const_var.hpp> |
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#include <boost/hof/always.hpp> |
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#include <boost/hof/function_param_limit.hpp> |
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namespace boost { namespace hof { |
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namespace detail { |
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// TODO: Make this work with fit_rewritable1_tag |
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template<std::size_t N, class F> |
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struct limit_adaptor : detail::callable_base<F> |
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{ |
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typedef std::integral_constant<std::size_t, N> fit_function_param_limit; |
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BOOST_HOF_INHERIT_CONSTRUCTOR(limit_adaptor, detail::callable_base<F>) |
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template<class... Ts> |
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constexpr const detail::callable_base<F>& base_function(Ts&&... xs) const |
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{ |
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return boost::hof::always_ref(*this)(xs...); |
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} |
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BOOST_HOF_RETURNS_CLASS(limit_adaptor); |
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template<class... Ts, class=typename std::enable_if<(sizeof...(Ts) <= N)>::type> |
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constexpr BOOST_HOF_SFINAE_RESULT(const detail::callable_base<F>&, id_<Ts>...) |
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operator()(Ts&&... xs) const BOOST_HOF_SFINAE_RETURNS |
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( |
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(BOOST_HOF_MANGLE_CAST(const detail::callable_base<F>&)(BOOST_HOF_CONST_THIS->base_function(xs...))) |
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(BOOST_HOF_FORWARD(Ts)(xs)...) |
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); |
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}; |
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template<std::size_t N> |
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struct make_limit_f |
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{ |
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constexpr make_limit_f() |
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{} |
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template<class F> |
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constexpr limit_adaptor<N, F> operator()(F f) const |
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{ |
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return limit_adaptor<N, F>(static_cast<F&&>(f)); |
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} |
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}; |
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struct limit_f |
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{ |
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template<class IntegralConstant, std::size_t N=IntegralConstant::type::value> |
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constexpr make_limit_f<N> operator()(IntegralConstant) const |
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{ |
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return {}; |
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} |
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}; |
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} |
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template<std::size_t N, class F> |
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constexpr detail::limit_adaptor<N, F> limit_c(F f) |
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{ |
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return detail::limit_adaptor<N, F>(static_cast<F&&>(f)); |
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} |
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BOOST_HOF_DECLARE_STATIC_VAR(limit, detail::limit_f); |
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}} // namespace boost::hof |
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#endif
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