composes two functions into one

src/FbTk/Compose.hh

@@ -0,0 +1,60 @@
+// Composer.hh
+// Copyright (c) 2003 Henrik Kinnunen (fluxgen at users.sourceforge.net)
+//
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the "Software"),
+// to deal in the Software without restriction, including without limitation
+// the rights to use, copy, modify, merge, publish, distribute, sublicense,
+// and/or sell copies of the Software, and to permit persons to whom the
+// Software is furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+// THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+// $Id: Compose.hh,v 1.1 2003/08/24 10:37:31 fluxgen Exp $
+
+#ifndef FBTK_COMPOSE_HH
+#define FBTK_COMPOSE_HH
+
+#include <functional>
+
+namespace FbTk {
+
+/// Composes two functions into one.
+/// Uses Arg for type B and then calls type A
+template <class A, class B>
+class Compose_base: public std::unary_function<typename B::argument_type, typename A::result_type> {
+public:
+    typedef typename A::result_type ResultTypeA;
+    typedef typename A::argument_type ArgumentTypeA;
+    typedef typename B::result_type ResultTypeB;
+    typedef typename B::argument_type ArgumentTypeB;
+
+    Compose_base(const A &a, const B &b):m_a(a), m_b(b) { }
+    ResultTypeA operator () (const ArgumentTypeB &arg) const {
+        return m_a(m_b(arg));
+    }
+
+private:
+    A m_a;
+    B m_b;
+};
+
+// helper that creates a Compose_base
+template <typename A, typename B>
+inline Compose_base<A, B> 
+Compose(const A& a, const B& b) {
+    return Compose_base<A, B>(a, b);
+}
+
+}; // namespace FbTk
+
+#endif // FBTK_COMPOSE_HH