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72 lines
1.7 KiB
C++
72 lines
1.7 KiB
C++
/*=============================================================================
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Copyright (c) 2015 Paul Fultz II
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eval.h
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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==============================================================================*/
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#ifndef FIT_GUARD_EVAL_H
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#define FIT_GUARD_EVAL_H
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/// eval
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/// ====
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///
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/// Description
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/// -----------
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///
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/// The `eval` function will evaluate a "thunk". This can be either a nullary
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/// function or it can be a an unary function that takes the identity function
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/// as the first parameter(which is helpful to delay compile-time checking).
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/// Also, additional parameters can be passed to `eval` to delay compiliation(so
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/// that result can depend on template parameters).
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///
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/// Synopsis
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/// --------
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///
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/// template<class F, class... Ts>
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/// constexpr auto eval(F&& f, Ts&&...);
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///
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/// Requirements
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/// ------------
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///
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/// F must be:
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///
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/// EvaluatableFunctionObject
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///
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/// Example
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/// -------
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///
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/// assert(fit::eval([]{ return 3; }) == 3);
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///
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#include <fit/always.h>
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#include <fit/identity.h>
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#include <fit/conditional.h>
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#include <fit/returns.h>
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namespace fit {
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namespace detail {
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struct simple_eval
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{
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template<class F, class... Ts>
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constexpr auto operator()(F&& f, Ts&&...xs) const FIT_RETURNS
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(fit::always_ref(f)(xs...)());
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};
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struct id_eval
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{
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template<class F, class... Ts>
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constexpr auto operator()(F&& f, Ts&&...xs) const FIT_RETURNS
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(fit::always_ref(f)(xs...)(fit::identity));
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};
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}
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FIT_DECLARE_STATIC_VAR(eval, fit::conditional_adaptor<detail::simple_eval, detail::id_eval>);
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}
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#endif
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