move monad to util

1 files changed, 66 insertions, 0 deletions

diff --git a/nihil.util/monad.test.cc b/nihil.util/monad.test.cc
new file mode 100644
index 0000000..bc9e406
--- /dev/null
+++ b/nihil.util/monad.test.cc
@@ -0,0 +1,66 @@
+// This source code is released into the public domain.
+
+#include <catch2/catch_test_macros.hpp>
+
+import nihil.std;
+import nihil.error;
+import nihil.util;
+
+namespace {
+TEST_CASE("monad: co_await std::optional<> with value", "[nihil]")
+{
+	auto get_value = [] -> std::optional<int> {
+		return 42;
+	};
+
+	auto try_get_value = [&get_value] -> std::optional<int> {
+		co_return co_await get_value();
+	};
+
+	auto o = try_get_value();
+	REQUIRE(o == 42);
+}
+
+TEST_CASE("monad: co_await std::optional<> without value", "[nihil]")
+{
+	auto get_value = [] -> std::optional<int> {
+		return {};
+	};
+
+	auto try_get_value = [&get_value] -> std::optional<int> {
+		co_return co_await get_value();
+	};
+
+	auto o = try_get_value();
+	REQUIRE(!o.has_value());
+}
+
+TEST_CASE("monad: co_await std::expected<> with value", "[nihil]")
+{
+	auto get_value = [] -> std::expected<int, std::string> {
+		return 42;
+	};
+
+	auto try_get_value = [&get_value] -> std::expected<int, std::string> {
+		co_return co_await get_value();
+	};
+
+	auto o = try_get_value();
+	REQUIRE(o == 42);
+}
+
+TEST_CASE("monad: co_await std::expected<> with error", "[nihil]")
+{
+	auto get_value = [] -> std::expected<int, std::string> {
+		return std::unexpected("error");
+	};
+
+	auto try_get_value = [&get_value] -> std::expected<int, std::string> {
+		co_return co_await get_value();
+	};
+
+	auto o = try_get_value();
+	REQUIRE(!o);
+	REQUIRE(o.error() == "error");
+}
+} // anonymous namespace