Utils: Add take

Add a new algorithmn to take the first match in a container out of the container.

It takes a pointer to something and will try to match against a smart pointer
stored in the container. Besides that it also accepts the usual like a predicate,
member variable or member function.

Change-Id: I4aabd4d43aa076a534da6488d0f9c3695ba79c09
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/libs/utils/algorithm.h

@@ -26,6 +26,7 @@
 #pragma once
 
 #include "predicates.h"
+#include "optional.h"
 
 #include <qcompilerdetection.h> // for Q_REQUIRED_RESULT
 
@@ -801,4 +802,36 @@ auto toConstReferences(const SourceContainer &sources)
     return transform(sources, [] (const auto &value) { return std::cref(value); });
 }
 
+//////////////////
+// take:
+/////////////////
+
+template<class C, typename P>
+Q_REQUIRED_RESULT Utils::optional<typename C::value_type> take(C &container, P predicate)
+{
+    const auto end = std::end(container);
+
+    const auto it = std::find_if(std::begin(container), end, predicate);
+    if (it == end)
+        return Utils::nullopt;
+
+    Utils::optional<typename C::value_type> result = Utils::make_optional(std::move(*it));
+    container.erase(it);
+    return result;
 }
+
+// pointer to member
+template <typename C, typename R, typename S>
+Q_REQUIRED_RESULT decltype(auto) take(C &container, R S::*member)
+{
+    return take(container, std::mem_fn(member));
+}
+
+// pointer to member function
+template <typename C, typename R, typename S>
+Q_REQUIRED_RESULT decltype(auto) take(C &container, R (S::*function)() const)
+{
+    return take(container, std::mem_fn(function));
+}
+
+} // namespace Utils

tests/auto/algorithm/tst_algorithm.cpp

@@ -50,6 +50,7 @@ private slots:
     void findOrDefault();
     void toRawPointer();
     void toReferences();
+    void take();
 };
 
 
@@ -612,6 +613,31 @@ void tst_Algorithm::toReferences()
     }
 }
 
+void tst_Algorithm::take()
+{
+    {
+        QList<Struct> v {1, 3, 5, 6, 7, 8, 9, 11, 13, 15, 13, 16, 17};
+        Utils::optional<Struct> r1 = Utils::take(v, [](const Struct &s) { return s.member == 13; });
+        QVERIFY(r1);
+        QCOMPARE(r1.value(), 13);
+        Utils::optional<Struct> r2 = Utils::take(v, [](const Struct &s) { return s.member == 13; });
+        QVERIFY(r2);
+        QCOMPARE(r2.value(), 13);
+        Utils::optional<Struct> r3 = Utils::take(v, [](const Struct &s) { return s.member == 13; });
+        QVERIFY(!r3);
+
+        Utils::optional<Struct> r4 = Utils::take(v, &Struct::isEven);
+        QVERIFY(r4);
+        QCOMPARE(r4.value(), 6);
+    }
+    {
+        QList<Struct> v {0, 0, 0, 0, 0, 0, 1, 2, 3};
+        Utils::optional<Struct> r1 = Utils::take(v, &Struct::member);
+        QVERIFY(r1);
+        QCOMPARE(r1.value(), 1);
+    }
+}
+
 QTEST_MAIN(tst_Algorithm)
 
 #include "tst_algorithm.moc"