Add invoke_r & co

asl/base/functional.hpp

@@ -54,6 +54,19 @@ constexpr auto invoke(is_func auto C::* f, auto&& self, Args&&... args)
     return ((*std::forward<decltype(self)>(self)).*f)(std::forward<Args>(args)...);
 }
 
+template<typename R, typename F, typename... Args>
+constexpr R invoke_r(F&& f, Args&&... args)
+{
+    if constexpr (is_void<R>)
+    {
+        static_cast<void>(invoke(std::forward<F>(f), std::forward<Args>(args)...));
+    }
+    else
+    {
+        return invoke(std::forward<F>(f), std::forward<Args>(args)...);
+    }
+}
+
 template<typename Void, typename F, typename... Args>
 struct _invoke_result_helper;
 
@@ -72,4 +85,8 @@ concept invocable = requires (F&& f, Args&&... args)
     invoke(std::forward<F>(f), std::forward<Args>(args)...);
 };
 
+template<typename R, typename F, typename... Args>
+concept invocable_r = invocable<F, Args...>
+    && (is_void<R> || convertible_to<invoke_result_t<F, Args...>, R>);
+
 } // namespace asl

asl/base/functional_tests.cpp

@@ -68,6 +68,9 @@ static_assert(asl::invocable<decltype(&HasMember::member), const HasMember2>);
 static_assert(asl::invocable<decltype(&HasMember::member), const HasMember&>);
 static_assert(asl::invocable<decltype(&HasMember::member), const HasMember2*>);
 
+static_assert(asl::invocable_r<void*, int*()>);
+static_assert(!asl::invocable_r<int*, void*()>);
+
 ASL_TEST(invoke_member_function)
 {
     HasFunction c;
@@ -109,3 +112,9 @@ ASL_TEST(invoke_lambda)
     ASL_TEST_EXPECT(asl::invoke([](){ return 35; }) == 35);
     ASL_TEST_EXPECT(asl::invoke([](int x){ return x + 2; }, 6) == 8);
 }
+
+ASL_TEST(invoke_r)
+{
+    ASL_TEST_EXPECT(asl::invoke_r<int>([]() { return 1ULL; }) == 1);
+    asl::invoke_r<void>([]() { return 1ULL; });
+}

todo.txt

@@ -1 +1 @@
-Add invoke_r & co
+