adding examples, fixing bugs

example/can_invoke/function_pointer.cpp

@@ -0,0 +1,28 @@
+/*!
+Copyright (c) 2016 Barrett Adair
+
+Distributed under the Boost Software License, Version 1.0.
+(See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
+*/
+
+#include <callable_traits/callable_traits.hpp>
+
+namespace ct = callable_traits;
+
+int foo(int&& i) {
+    return i;
+}
+
+// can_invoke returns std::true_type here because the
+// arguments are valid to INVOKE
+static_assert(ct::can_invoke(&foo, 0), "");
+
+int i = 0;
+
+// can_invoke returns std::false_type here because the
+// arguments are NOT valid to INVOKE - foo expects an
+// rvalue reference, not an lvalue reference.
+static_assert(!ct::can_invoke(&foo, i), "");
+
+int main() { return 0; }
+