feat():initial version

install/boost_1_75_0/include/boost/hof/limit.hpp

@@ -0,0 +1,142 @@
+/*=============================================================================
+    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