Utils: Add predicates for comparison to constant values

Many STL algorithms have value version. So you can only use a predicate:

std::stable_partition(std::begin(list), std::end(list), [](int entry) {
     return entry < 20;
});

With this predicates you can write it in a shorter form:

std::stable_partition(std::begin(list), std::end(list), lessThan(20));

The find helpers are moved to predicates too.

Change-Id: I791b3105ca84ef7c5a519d22589a91b5548cf3e4
Reviewed-by: Orgad Shaneh <orgads@gmail.com>
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

1 files changed, 132 insertions, 0 deletions

diff --git a/src/libs/utils/predicates.h b/src/libs/utils/predicates.h
new file mode 100644
index 00000000000..cda721ad21b
--- /dev/null
+++ b/src/libs/utils/predicates.h
@@ -0,0 +1,132 @@
+/****************************************************************************
+**
+** Copyright (C) 2017 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of Qt Creator.
+**
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3 as published by the Free Software
+** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-3.0.html.
+**
+****************************************************************************/
+
+#pragma once
+
+#include <functional>
+#include <type_traits>
+#include <utility>
+
+namespace Utils
+{
+
+//////////////////
+// find helpers
+//////////////////
+template<typename R, typename S, typename T>
+decltype(auto) equal(R (S::*function)() const, T value)
+{
+    // This should use std::equal_to<> instead of std::equal_to<T>,
+    // but that's not supported everywhere yet, since it is C++14
+    return std::bind<bool>(std::equal_to<T>(), value, std::bind(function, std::placeholders::_1));
+}
+
+template<typename R, typename S, typename T>
+decltype(auto) equal(R S::*member, T value)
+{
+    return std::bind<bool>(std::equal_to<T>(), value, std::bind(member, std::placeholders::_1));
+}
+
+//////////////////
+// comparison predicates
+//////////////////
+template <typename Type>
+auto equalTo(Type &&value)
+{
+    return [value = std::forward<Type>(value)] (const auto &entry)
+    {
+        static_assert(std::is_same<std::decay_t<Type>,
+                      std::decay_t<decltype(entry)>>::value,
+                      "The container and predicate type of equalTo should be the same to prevent "
+                      "unnecessary conversion.");
+        return entry == value;
+    };
+}
+
+template <typename Type>
+auto unequalTo(Type &&value)
+{
+    return [value = std::forward<Type>(value)] (const auto &entry)
+    {
+        static_assert(std::is_same<std::decay_t<Type>,
+                      std::decay_t<decltype(entry)>>::value,
+                      "The container and predicate type of unequalTo should be the same to prevent "
+                      "unnecessary conversion.");
+        return !(entry == value);
+    };
+}
+
+template <typename Type>
+auto lessThan(Type &&value)
+{
+    return [value = std::forward<Type>(value)] (const auto &entry)
+    {
+        static_assert(std::is_same<std::decay_t<Type>,
+                      std::decay_t<decltype(entry)>>::value,
+                      "The container and predicate type of unequalTo should be the same to prevent "
+                      "unnecessary conversion.");
+        return entry < value;
+    };
+}
+
+template <typename Type>
+auto lessEqualThan(Type &&value)
+{
+    return [value = std::forward<Type>(value)] (const auto &entry)
+    {
+        static_assert(std::is_same<std::decay_t<Type>,
+                      std::decay_t<decltype(entry)>>::value,
+                      "The container and predicate type of lessEqualThan should be the same to "
+                      "prevent unnecessary conversion.");
+        return !(value < entry);
+    };
+}
+
+template <typename Type>
+auto greaterThan(Type &&value)
+{
+    return [value = std::forward<Type>(value)] (const auto &entry)
+    {
+        static_assert(std::is_same<std::decay_t<Type>,
+                      std::decay_t<decltype(entry)>>::value,
+                      "The container and predicate type of greaterThan should be the same to "
+                      "prevent unnecessary conversion.");
+        return value < entry;
+    };
+}
+
+template <typename Type>
+auto greaterEqualThan(Type &&value)
+{
+    return [value = std::forward<Type>(value)] (const auto &entry)
+    {
+        static_assert(std::is_same<std::decay_t<Type>,
+                      std::decay_t<decltype(entry)>>::value,
+                      "The container and predicate type of greaterEqualThan should be the same to "
+                      "prevent unnecessary conversion.");
+        return !(entry < value);
+    };
+}
+} // namespace Utils