1 files changed, 65 insertions, 0 deletions
diff --git a/asl/base/functional.hpp b/asl/base/functional.hpp
new file mode 100644
index 0000000..d820bce
--- /dev/null
+++ b/asl/base/functional.hpp
@@ -0,0 +1,65 @@
+#pragma once
+
+#include "asl/base/meta.hpp"
+#include "asl/base/utility.hpp"
+
+namespace asl {
+
+template<typename... Args, typename C>
+constexpr auto invoke(is_func auto C::* f, auto&& self, Args&&... args)
+    requires requires {
+        (self.*f)(ASL_FWD(args)...);
+    }
+{
+    return (ASL_FWD(self).*f)(ASL_FWD(args)...);
+}
+
+template<typename... Args, typename C>
+constexpr auto invoke(is_func auto C::* f, auto* self, Args&&... args)
+    requires requires {
+        (self->*f)(ASL_FWD(args)...);
+    }
+{
+    return (self->*f)(ASL_FWD(args)...);
+}
+
+template<typename... Args, typename C>
+constexpr auto invoke(is_object auto C::* m, auto&& self, Args&&...)
+    requires (
+        sizeof...(Args) == 0 &&
+        requires { self.*m; }
+    )
+{
+    return ASL_FWD(self).*m;
+}
+
+template<typename... Args, typename C>
+constexpr auto invoke(is_object auto C::* m, auto* self, Args&&...)
+    requires (
+        sizeof...(Args) == 0 &&
+        requires { self->*m; }
+    )
+{
+    return self->*m;
+}
+
+template<typename... Args>
+constexpr auto invoke(auto&& f, Args&&... args)
+    requires requires {
+        f(ASL_FWD(args)...);
+    }
+{
+    return ASL_FWD(f)(ASL_FWD(args)...);
+}
+
+template<typename F> struct _result_of_helper;
+
+template<typename R, typename... Args>
+struct _result_of_helper<R(Args...)>
+{
+    using type = decltype(invoke(declval<R>(), declval<Args>()...));
+};
+
+template<typename F> using result_of_t = _result_of_helper<F>::type;
+
+} // namespace asl