container: add free 'contains' query

CMakeLists.txt

@@ -288,6 +288,7 @@ list (
     cmdopt.hpp
     colour.cpp
     colour.hpp
+    container.hpp
     coord.hpp
     coord/fwd.hpp
     coord/base.hpp

container.hpp

@@ -0,0 +1,32 @@
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ *
+ * Copyright 2020, Danny Robson <danny@nerdcruft.net>
+ */
+
+#pragma once
+
+#include <algorithm>
+#include <utility>
+
+namespace cruft {
+    /// Tests if a value is present in a container.
+    ///
+    /// Defaults to a naive search of the container.
+    ///
+    /// \return true if the value is present in the container, otherwise false.
+    template <typename ContainerT, typename ValueT>
+    bool
+    contains (ValueT &&value, ContainerT &&container)
+    {
+        auto const pos = std::find (
+            std::cbegin (container),
+            std::cend   (container),
+            std::move (value)
+        );
+
+        return pos != std::cend (container);
+    }
+}