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Telegram/lib_base/base/functors.h

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+// This file is part of Desktop App Toolkit,
+// a set of libraries for developing nice desktop applications.
+//
+// For license and copyright information please follow this link:
+// https://github.com/desktop-app/legal/blob/master/LEGAL
+//
+#pragma once
+
+namespace base {
+namespace functors {
+
+struct abs_helper {
+	template <
+		typename Type,
+		typename = decltype(0 < std::declval<Type>()),
+		typename = decltype(-std::declval<Type>())>
+	constexpr Type operator()(Type value) const {
+		return (0 < value) ? value : (-value);
+	}
+};
+constexpr auto abs = abs_helper{};
+
+constexpr auto add = [](auto value) {
+	return [value](auto other) {
+		return value + other;
+	};
+};
+
+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