2983: Add map_result function for void result

HarrievG · Jul 14, 2020 · 533e69f · 533e69f
1 parent 030b4e5
commit 533e69f
Show file tree

Hide file tree

Showing 2 changed files with 65 additions and 0 deletions.
diff --git a/lib/kdl/include/kdl/result.h b/lib/kdl/include/kdl/result.h
@@ -462,6 +462,62 @@ namespace kdl {
                 return visitor();
             }
         }
+
+        /**
+         * Applies the given function to given result and returns a new result with the result type of
+         * the given function as its value type.
+         *
+         * If the given result is a success, the function is applied and the result of applying the
+         * function is returned wrapped in a result.
+         * If the given result contains an error, that error is returned as is.
+         *
+         * @tparam F the type of the function to apply
+         * @param f the function to apply
+         * @param result_ the result to map
+         */
+        template <typename F>
+        friend auto map_result(F&& f, const result& result_) {
+            using R = std::invoke_result_t<F>;
+            if constexpr (std::is_same_v<R, void>) {
+                return visit_result(kdl::overload {
+                    [&]()              { f(); return result<R, Errors...>::success(); },
+                    [] (const auto& e) { return result<R, Errors...>::error(e); }
+                }, result_);
+            } else {
+                return visit_result(kdl::overload {
+                    [&]()              { return result<R, Errors...>::success(f()); },
+                    [] (const auto& e) { return result<R, Errors...>::error(e); }
+                }, result_);
+            }
+        }
+
+        /**
+         * Applies the given function to given result and returns a new result with the result type of
+         * the given function as its value type.
+         *
+         * If the given result is a success, the function is applied and the result of applying the
+         * function is returned wrapped in a result.
+         * If the given result contains an error, that error is returned as is.
+         *
+         * @tparam F the type of the function to apply
+         * @param f the function to apply
+         * @param result_ the result to map
+         */
+        template <typename F>
+        friend auto map_result(F&& f, result&& result_) {
+            using R = std::invoke_result_t<F>;
+            if constexpr (std::is_same_v<R, void>) {
+                return visit_result(kdl::overload {
+                    [&]()              { f(); return result<R, Errors...>::success(); },
+                    [] (const auto& e) { return result<R, Errors...>::error(e); }
+                }, std::move(result_));
+            } else {
+                return visit_result(kdl::overload {
+                    [&]()              { return result<R, Errors...>::success(f()); },
+                    [] (const auto& e) { return result<R, Errors...>::error(e); }
+                }, std::move(result_));
+            }
+        }
 
         /**
          * Indicates whether this result is empty.

diff --git a/lib/kdl/test/src/result_test.cpp b/lib/kdl/test/src/result_test.cpp
@@ -414,6 +414,15 @@ namespace kdl {
         test_visit_error_rvalue_ref_with_opt_value<result<void, Counter, Error2>>(Counter{});
     }
 
+    TEST_CASE("void_result_test.map", "[void_result_test]") {
+        CHECK(result<bool, Error1, Error2>::success(true) == map_result(
+            []() { return true; },
+            result<void, Error1, Error2>::success()));
+        CHECK(result<bool, Error1, Error2>::error(Error2{}) == map_result(
+            []() { return true; },
+            result<void, Error1, Error2>::error(Error2{})));
+    }
+
     TEST_CASE("opt_result_test.constructor", "[opt_result_test]") {
         ASSERT_TRUE((result<opt<int>, float, std::string>::success().is_success()));
         ASSERT_TRUE((result<opt<int>, float, std::string>::success(1).is_success()));