Edit: /usr/include/boost/hof/eval.hpp (2400B)
/*=============================================================================
Copyright (c) 2015 Paul Fultz II
eval.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_EVAL_H
#define BOOST_HOF_GUARD_EVAL_H
/// eval
/// ====
///
/// Description
/// -----------
///
/// The `eval` function will evaluate a "thunk". This can be either a nullary
/// function or it can be a unary function that takes the identity function as
/// the first parameter(which is helpful to delay compile-time checking).
/// Also, additional parameters can be passed to `eval` to delay
/// compiliation(so that result can depend on template parameters).
///
/// Synopsis
/// --------
///
/// template
/// constexpr auto eval(F&& f, Ts&&...);
///
/// Requirements
/// ------------
///
/// F must be:
///
/// * [EvaluatableFunctionObject](EvaluatableFunctionObject)
///
/// Example
/// -------
///
/// #include
/// #include
///
/// int main() {
/// assert(boost::hof::eval([]{ return 3; }) == 3);
/// }
///
/// References
/// ----------
///
/// * [POO51](http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0051r2.pdf) - Proposal for C++
/// Proposal for C++ generic overload function
/// * [static_if](static_if)
/// * [Ordering evaluation of arguments]()
///
#include
#include
#include
#include
namespace boost { namespace hof {
namespace detail {
struct simple_eval
{
template
constexpr BOOST_HOF_SFINAE_RESULT(F)
operator()(F&& f, Ts&&...xs) const BOOST_HOF_SFINAE_RETURNS
(boost::hof::always_ref(f)(xs...)());
};
struct id_eval
{
template
constexpr BOOST_HOF_SFINAE_RESULT(F, id_)
operator()(F&& f, Ts&&...xs) const BOOST_HOF_SFINAE_RETURNS
(boost::hof::always_ref(f)(xs...)(boost::hof::identity));
};
}
BOOST_HOF_DECLARE_STATIC_VAR(eval, boost::hof::first_of_adaptor);
}} // namespace boost::hof
#endif