tdesktop/Telegram/SourceFiles/base/functors.h

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/*
This file is part of Telegram Desktop,
the official desktop version of Telegram messaging app, see https://telegram.org
Telegram Desktop is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
It is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
In addition, as a special exception, the copyright holders give permission
to link the code of portions of this program with the OpenSSL library.
Full license: https://github.com/telegramdesktop/tdesktop/blob/master/LICENSE
Copyright (c) 2014-2017 John Preston, https://desktop.telegram.org
*/
#pragma once
namespace base {
namespace functors {
struct abs_helper {
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template <
typename Type,
typename = decltype(0 < std::declval<Type>()),
typename = decltype(-std::declval<Type>())>
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constexpr Type operator()(Type value) const {
return (0 < value) ? value : (-value);
}
};
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constexpr auto abs = abs_helper{};
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constexpr auto add = [](auto value) {
return [value](auto other) {
return value + other;
};
};
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struct negate_helper {
template <
typename Type,
typename = decltype(-std::declval<Type>())>
constexpr Type operator()(Type value) const {
return -value;
}
};
constexpr auto negate = negate_helper{};
} // namespace functors
} // namespace base