renaming function qualifier manipulations

example/add_function_lvalue.cpp

@@ -0,0 +1,53 @@
+/*<-
+Copyright Barrett Adair 2016
+Distributed under the Boost Software License, Version 1.0.
+(See accompanying file LICENSE.md or copy at http ://boost.org/LICENSE_1_0.txt)
+->*/
+
+//[ add_function_lvalue
+#include <type_traits>
+#include <callable_traits/add_function_lvalue.hpp>
+
+namespace ct = callable_traits;
+
+struct foo {};
+
+int main() {
+
+    {
+        using pmf = void(foo::*)();
+        using expect = void(foo::*)() &;
+        using test = ct::add_function_lvalue<pmf>;
+        static_assert(std::is_same<test, expect>::value, "");
+    } {
+        // add_function_lvalue doesn't change anything when
+        // the function type already has an lvalue qualifier.
+        using pmf = void(foo::*)() &;
+        using expect = void(foo::*)() &;
+        using test = ct::add_function_lvalue<pmf>;
+        static_assert(std::is_same<test, expect>::value, "");
+    } {
+        // add_function_lvalue models C++11 reference collapsing
+        // rules, so that adding an lvalue qualifier to an
+        // rvalue-qualified type will force the lvalue.
+        using pmf = void(foo::*)() &&;
+        using expect = void(foo::*)() &;
+        using test = ct::add_function_lvalue<pmf>;
+        static_assert(std::is_same<test, expect>::value, "");
+    } {
+        // add_function_lvalue can also be used to create "abominable"
+        // function types.
+        using f = void();
+        using expect = void() &;
+        using test = ct::add_function_lvalue<f>;
+        static_assert(std::is_same<test, expect>::value, "");
+    } {
+        // add_function_lvalue has no affect on function pointers,
+        // function references, function objects, or member data pointers.
+        using f = int foo::*;
+        using expect = int foo::*;
+        using test = ct::add_function_lvalue<f>;
+        static_assert(std::is_same<test, expect>::value, "");
+    }
+}
+//]