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/*=============================================================================
    Copyright (c) 2014 Paul Fultz II
    lambda.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_LAMBDA_H
#define BOOST_HOF_GUARD_FUNCTION_LAMBDA_H

/// BOOST_HOF_STATIC_LAMBDA
/// =================
/// 
/// Description
/// -----------
/// 
/// The `BOOST_HOF_STATIC_LAMBDA` macro allows initializing non-capturing lambdas at
/// compile-time in a `constexpr` expression.
/// 
/// Example
/// -------
/// 
///     #include <boost/hof.hpp>
///     #include <cassert>
/// 
///     const constexpr auto add_one = BOOST_HOF_STATIC_LAMBDA(int x)
///     {
///         return x + 1;
///     };
/// 
///     int main() {
///         assert(3 == add_one(2));
///     }
/// 
/// BOOST_HOF_STATIC_LAMBDA_FUNCTION
/// ==========================
/// 
/// Description
/// -----------
/// 
/// The `BOOST_HOF_STATIC_LAMBDA_FUNCTION` macro allows initializing a global
/// function object that contains non-capturing lambdas. It also ensures that
/// the global function object has a unique address across translation units.
/// This helps prevent possible ODR-violations.
/// 
/// By default, all functions defined with `BOOST_HOF_STATIC_LAMBDA_FUNCTION` use
/// the `boost::hof::reveal` adaptor to improve error messages.
/// 
/// Example
/// -------
/// 
///     #include <boost/hof.hpp>
///     #include <cassert>
/// 
///     BOOST_HOF_STATIC_LAMBDA_FUNCTION(add_one) = [](int x)
///     {
///         return x + 1;
///     };
///     int main() {
///         assert(3 == add_one(2));
///     }
/// 

#include <boost/hof/config.hpp>

// TODO: Move this to a detail header
#if !BOOST_HOF_HAS_CONSTEXPR_LAMBDA || !BOOST_HOF_HAS_INLINE_LAMBDAS

#include <type_traits>
#include <utility>
#include <boost/hof/detail/result_of.hpp>
#include <boost/hof/reveal.hpp>
#include <boost/hof/detail/constexpr_deduce.hpp>
#include <boost/hof/function.hpp>


#ifndef BOOST_HOF_REWRITE_STATIC_LAMBDA
#ifdef _MSC_VER
#define BOOST_HOF_REWRITE_STATIC_LAMBDA 1
#else
#define BOOST_HOF_REWRITE_STATIC_LAMBDA 0
#endif
#endif

namespace boost { namespace hof {

namespace detail {

template<class F>
struct static_function_wrapper
{
    // Default constructor necessary for MSVC
    constexpr static_function_wrapper()
    {}

    static_assert(BOOST_HOF_IS_EMPTY(F), "Function or lambda expression must be empty");

    struct failure
    : failure_for<F>
    {};

    template<class... Ts>
    const F& base_function(Ts&&...) const