constantly.hpp

Go to the documentation of this file.

//
// Copyright (C) 2014, 2015 Ableton AG, Berlin. All rights reserved.
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the "Software"),
// to deal in the Software without restriction, including without limitation
// the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
// THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.
//

#pragma once

#include <atria/estd/type_traits.hpp>
#include <atria/meta/utils.hpp>
#include <utility>

namespace atria {
namespace prelude {

template <typename T>
struct constantly_t
{
  T value;

  template <typename ...ArgTs>
  auto operator() (ArgTs&&...) & -> T& { return value; }
  template <typename ...ArgTs>
  auto operator() (ArgTs&&...) const& -> const T& { return value; }
  template <typename ...ArgTs>
  auto operator() (ArgTs&&...) && -> T&& { return std::move(value); }
};

template <typename T>
auto constantly(T&& value)
  -> constantly_t<estd::decay_t<T> >
{
  return constantly_t<estd::decay_t<T> >{ std::forward<T>(value) };
}

} // namespace prelude

using prelude::constantly_t;
using prelude::constantly;

} // namespace atria