Added thirdparty: boost library

thirdparty/include/boost/hof/first_of.hpp

@@ -0,0 +1,244 @@
+/*=============================================================================
+    Copyright (c) 2012 Paul Fultz II
+    first_of.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_CONDITIONAL_H
+#define BOOST_HOF_GUARD_FUNCTION_CONDITIONAL_H
+
+/// first_of
+/// ========
+/// 
+/// Description
+/// -----------
+/// 
+/// The `first_of` function adaptor combines several functions together. If
+/// the first function can not be called, then it will try to call the next
+/// function. This can be very useful when overloading functions using
+/// template constraints(such as with `enable_if`).
+/// 
+/// Note: This is different than the [`match`](match.md) function adaptor, which
+/// can lead to ambiguities. Instead, `first_of` will call the first function
+/// that is callable, regardless if there is another function that could be
+/// called as well.
+/// 
+/// Synopsis
+/// --------
+/// 
+///     template<class... Fs>
+///     constexpr first_of_adaptor<Fs...> first_of(Fs... fs);
+/// 
+/// Requirements
+/// ------------
+/// 
+/// Fs must be:
+/// 
+/// * [ConstInvocable](ConstInvocable)
+/// * MoveConstructible
+/// 
+/// Example
+/// -------
+/// 
+///     #include <boost/hof.hpp>
+///     #include <iostream>
+///     using namespace boost::hof;
+/// 
+///     struct for_ints
+///     {
+///         void operator()(int) const
+///         {
+///             printf("Int\n");
+///         }
+///     };
+/// 
+///     struct for_floats
+///     {
+///         void operator()(float) const
+///         {
+///             printf("Float\n");
+///         }
+///     };
+/// 
+///     int main() {
+///         first_of(for_ints(), for_floats())(3.0);
+///     }
+/// 
+/// This will print `Int` because the `for_floats` function object won't ever be
+/// called. Due to the conversion rules in C++, the `for_ints` function can be
+/// called on floats, so it is chosen by `first_of` first, even though
+/// `for_floats` is a better match.
+/// 
+/// So, the order of the functions in the `first_of_adaptor` are very important
+/// to how the function is chosen.
+/// 
+/// References
+/// ----------
+/// 
+/// * [POO51](http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0051r2.pdf) - Proposal for C++
+///   Proposal for C++ generic overload function
+/// * [Conditional overloading](<Conditional overloading>)
+/// 
+
+#include <boost/hof/reveal.hpp>
+#include <boost/hof/detail/compressed_pair.hpp>
+#include <boost/hof/detail/callable_base.hpp>
+#include <boost/hof/detail/delegate.hpp>
+#include <boost/hof/detail/join.hpp>
+#include <boost/hof/detail/seq.hpp>
+#include <boost/hof/detail/make.hpp>
+#include <boost/hof/detail/static_const_var.hpp>
+
+namespace boost { namespace hof {
+
+namespace detail {
+
+template<class F1, class F2>
+struct basic_first_of_adaptor : F1, F2
+{
+    BOOST_HOF_INHERIT_DEFAULT(basic_first_of_adaptor, F1, F2)
+
+    template<class A, class B,
+        BOOST_HOF_ENABLE_IF_CONVERTIBLE(A, F1),
+        BOOST_HOF_ENABLE_IF_CONVERTIBLE(B, F2)>
+    constexpr basic_first_of_adaptor(A&& f1, B&& f2)
+    noexcept(BOOST_HOF_IS_NOTHROW_CONSTRUCTIBLE(F1, A&&) && BOOST_HOF_IS_NOTHROW_CONSTRUCTIBLE(F2, B&&))
+    : F1(BOOST_HOF_FORWARD(A)(f1)), F2(BOOST_HOF_FORWARD(B)(f2))
+    {}
+
+    template<class X,
+        class=typename std::enable_if<
+        BOOST_HOF_IS_CONVERTIBLE(X, F1) && 
+        BOOST_HOF_IS_DEFAULT_CONSTRUCTIBLE(F2)
+    >::type>
+    constexpr basic_first_of_adaptor(X&& x) 
+    BOOST_HOF_NOEXCEPT_CONSTRUCTIBLE(F1, X&&)
+    : F1(BOOST_HOF_FORWARD(X)(x))
+    {} 
+
+    template<class... Ts>
+    struct select
+    : std::conditional
+    <
+        is_invocable<F1, Ts...>::value, 
+        F1,
+        F2
+    >
+    {};
+
+    BOOST_HOF_RETURNS_CLASS(basic_first_of_adaptor);
+
+    template<class... Ts, class F=typename select<Ts...>::type>
+    constexpr BOOST_HOF_SFINAE_RESULT(typename select<Ts...>::type, id_<Ts>...) 
+    operator()(Ts && ... xs) const
+    BOOST_HOF_SFINAE_RETURNS
+    (
+        BOOST_HOF_RETURNS_STATIC_CAST(const F&)(*BOOST_HOF_CONST_THIS)(BOOST_HOF_FORWARD(Ts)(xs)...)
+    );
+};
+
+template <class F1, class F2>
+constexpr const F1& which(std::true_type, const F1& f1, const F2&) noexcept
+{ 
+    return f1; 
+}
+
+template <class F1, class F2>
+constexpr const F2& which(std::false_type, const F1&, const F2& f2) noexcept
+{ 
+    return f2; 
+}
+
+template<class F1, class F2>
+struct conditional_kernel : compressed_pair<F1, F2>
+{
+    typedef compressed_pair<F1, F2> base;
+    BOOST_HOF_INHERIT_CONSTRUCTOR(conditional_kernel, base)
+
+    template<class... Ts>
+    struct select
+    : std::conditional
+    <
+        is_invocable<F1, Ts...>::value, 
+        F1,
+        F2
+    >
+    {};
+
+    BOOST_HOF_RETURNS_CLASS(conditional_kernel);
+
+    template<class... Ts, class PickFirst=is_invocable<F1, Ts...>>
+    constexpr BOOST_HOF_SFINAE_RESULT(typename select<Ts...>::type, id_<Ts>...) 
+    operator()(Ts && ... xs) const
+    BOOST_HOF_SFINAE_RETURNS
+    (
+        boost::hof::detail::which(
+            BOOST_HOF_RETURNS_CONSTRUCT(PickFirst)(),
+            BOOST_HOF_MANGLE_CAST(const F1&)(BOOST_HOF_CONST_THIS->first(xs...)),
+            BOOST_HOF_MANGLE_CAST(const F2&)(BOOST_HOF_CONST_THIS->second(xs...))
+        )
+        (BOOST_HOF_FORWARD(Ts)(xs)...)
+    );
+};
+}
+
+template<class F, class... Fs>
+struct first_of_adaptor 
+: detail::conditional_kernel<F, BOOST_HOF_JOIN(first_of_adaptor, Fs...) >
+{
+    typedef first_of_adaptor fit_rewritable_tag;
+    typedef BOOST_HOF_JOIN(first_of_adaptor, Fs...) kernel_base;
+    typedef detail::conditional_kernel<F, kernel_base > base;
+
+    BOOST_HOF_INHERIT_DEFAULT(first_of_adaptor, base)
+
+    template<class X, class... Xs, 
+        BOOST_HOF_ENABLE_IF_CONSTRUCTIBLE(base, X, kernel_base), 
+        BOOST_HOF_ENABLE_IF_CONSTRUCTIBLE(kernel_base, Xs...)>
+    constexpr first_of_adaptor(X&& f1, Xs&& ... fs) 
+    noexcept(BOOST_HOF_IS_NOTHROW_CONSTRUCTIBLE(base, X&&, kernel_base) && BOOST_HOF_IS_NOTHROW_CONSTRUCTIBLE(kernel_base, Xs&&...))
+    : base(BOOST_HOF_FORWARD(X)(f1), kernel_base(BOOST_HOF_FORWARD(Xs)(fs)...))
+    {}
+
+    template<class X, class... Xs, 
+        BOOST_HOF_ENABLE_IF_CONSTRUCTIBLE(base, X)>
+    constexpr first_of_adaptor(X&& f1) 
+    BOOST_HOF_NOEXCEPT_CONSTRUCTIBLE(base, X&&)
+    : base(BOOST_HOF_FORWARD(X)(f1))
+    {}
+
+    struct failure
+    : failure_for<F, Fs...>
+    {};
+};
+
+template<class F>
+struct first_of_adaptor<F> : F
+{
+    typedef first_of_adaptor fit_rewritable_tag;
+    BOOST_HOF_INHERIT_CONSTRUCTOR(first_of_adaptor, F);
+
+    struct failure
+    : failure_for<F>
+    {};
+};
+
+template<class F1, class F2>
+struct first_of_adaptor<F1, F2> 
+: detail::conditional_kernel<F1, F2>
+{
+    typedef detail::conditional_kernel<F1, F2> base;
+    typedef first_of_adaptor fit_rewritable_tag;
+    BOOST_HOF_INHERIT_CONSTRUCTOR(first_of_adaptor, base);
+
+    struct failure
+    : failure_for<F1, F2>
+    {};
+};
+
+BOOST_HOF_DECLARE_STATIC_VAR(first_of, detail::make<first_of_adaptor>);
+
+}} // namespace boost::hof
+
+#endif