Imported Upstream version 1.67.0upstream/1.67.0

1 files changed, 133 insertions, 0 deletions

diff --git a/boost/hof/indirect.hpp b/boost/hof/indirect.hpp
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+/*=============================================================================
+    Copyright (c) 2014 Paul Fultz II
+    indirect.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_INDIRECT_H
+#define BOOST_HOF_GUARD_FUNCTION_INDIRECT_H
+
+/// indirect
+/// ========
+/// 
+/// Description
+/// -----------
+/// 
+/// The `indirect` function adaptor dereferences the object before calling it.
+/// 
+/// Synopsis
+/// --------
+/// 
+///     template<class F>
+///     constexpr indirect_adaptor<F> indirect(F f);
+/// 
+/// Semantics
+/// ---------
+/// 
+///     assert(indirect(f)(xs...) == (*f)(xs...));
+/// 
+/// Requirements
+/// ------------
+/// 
+/// F must be:
+/// 
+/// * MoveConstructible
+/// * Dereferenceable
+/// 
+/// Example
+/// -------
+/// 
+///     #include <boost/hof.hpp>
+///     #include <cassert>
+///     #include <memory>
+///     using namespace boost::hof;
+/// 
+///     struct sum
+///     {
+///         template<class T, class U>
+///         T operator()(T x, U y) const
+///         {
+///             return x+y;
+///         }
+///     };
+/// 
+///     int main() {
+///         int r = indirect(std::make_unique<sum>())(3,2);
+///         assert(r == 5);
+///     }
+/// 
+
+#include <boost/hof/detail/delegate.hpp>
+#include <boost/hof/detail/result_of.hpp>
+#include <boost/hof/reveal.hpp>
+#include <boost/hof/always.hpp>
+#include <boost/hof/detail/move.hpp>
+#include <boost/hof/detail/make.hpp>
+#include <boost/hof/detail/static_const_var.hpp>
+
+namespace boost { namespace hof {
+// TODO: Support non-classes as well
+template<class F>
+struct indirect_adaptor : F
+{
+    typedef indirect_adaptor fit_rewritable1_tag;
+    BOOST_HOF_INHERIT_CONSTRUCTOR(indirect_adaptor, F);
+
+    template<class... Ts>
+    constexpr const F& base_function(Ts&&... xs) const noexcept
+    {
+        return boost::hof::always_ref(*this)(xs...);
+    }
+
+    struct failure
+    : failure_for<decltype(*std::declval<F>())>
+    {};
+
+    BOOST_HOF_RETURNS_CLASS(indirect_adaptor);
+
+    template<class... Ts>
+    constexpr BOOST_HOF_SFINAE_RESULT(decltype(*std::declval<F>()), id_<Ts>...) 
+    operator()(Ts&&... xs) const BOOST_HOF_SFINAE_RETURNS
+    (
+        (*BOOST_HOF_MANGLE_CAST(const F&)(BOOST_HOF_CONST_THIS->base_function(xs...)))(BOOST_HOF_FORWARD(Ts)(xs)...)
+    );
+};
+
+template<class F>
+struct indirect_adaptor<F*>
+{
+    typedef indirect_adaptor fit_rewritable1_tag;
+    F* f;
+    constexpr indirect_adaptor() noexcept
+    {}
+
+    constexpr indirect_adaptor(F* x) noexcept
+    : f(x)
+    {}
+
+    template<class... Ts>
+    constexpr F& base_function(Ts&&...) const noexcept
+    {
+        return *f;
+    }
+
+    struct failure
+    : failure_for<F>
+    {};
+
+    BOOST_HOF_RETURNS_CLASS(indirect_adaptor);
+
+    template<class... Ts>
+    constexpr BOOST_HOF_SFINAE_RESULT(F, id_<Ts>...) 
+    operator()(Ts&&... xs) const BOOST_HOF_SFINAE_RETURNS
+    (
+        (BOOST_HOF_MANGLE_CAST(F&)(BOOST_HOF_CONST_THIS->base_function(xs...)))(BOOST_HOF_FORWARD(Ts)(xs)...)
+    );
+};
+
+BOOST_HOF_DECLARE_STATIC_VAR(indirect, detail::make<indirect_adaptor>);
+
+}} // namespace boost::hof
+
+#endif