fn: add simple fn signature checker example

1 files changed, 32 insertions, 0 deletions

diff --git a/fn_alias.cc b/fn_alias.cc
new file mode 100644
index 0000000..2d9fd1d
--- /dev/null
+++ b/fn_alias.cc
@@ -0,0 +1,32 @@
+#include <cassert>
+#include <cstdio>
+
+// Function alias.
+
+void say() {
+  std::puts("say");
+}
+
+inline constexpr auto say_alias = say;
+
+// Template function alias.
+//
+// One drawback is that template type deducation does not work through the
+// function pointer. One would need to write some macro wrapper.
+
+template <typename T, typename U>
+auto add(T t, U u) -> decltype(t + u) {
+  return t + u;
+}
+
+template <typename U>
+inline constexpr auto add_int = add<int, U>;
+
+// Test me.
+
+int main() {
+  say();
+  say_alias();
+
+  assert(add(2, 3) == add_int<int>(3, 2));
+}