documentation and examples

example/can_invoke_constexpr_function_pointer.cpp

@@ -0,0 +1,39 @@
+/*!<-
+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)
+->*/
+
+//[ can_invoke_constexpr_function_pointer
+#include <type_traits>
+#include <callable_traits/callable_traits.hpp>
+
+namespace ct = callable_traits;
+
+constexpr int seven(int) {
+    return 7;
+}
+
+using seven_c = std::integral_constant<decltype(&seven), &seven>;
+
+// The first call to can_invoke_constexpr returns std::true_type
+// because `seven` is a constexpr function, and valid INVOKE arguments
+// are passed. The second call to can_invoke_constexpr returns
+// std::false_type, because the arguments are not valid to INVOKE
+static_assert(ct::can_invoke_constexpr(seven_c{}, 0), "");
+static_assert(!ct::can_invoke_constexpr(seven_c{}, nullptr), "");
+
+int eight(int) {
+    return 7;
+}
+
+using eight_c = std::integral_constant<decltype(&eight), &eight>;
+
+// `eight` is NOT a constexpr function, so can_invoke_constexpr
+// returns `std::false_type` even for valid INVOKE arguments.
+static_assert(!ct::can_invoke_constexpr(eight_c{}, 0), "");
+static_assert(!ct::can_invoke_constexpr(eight_c{}, nullptr), "");
+
+int main() {}
+//]