expression: add new built in "reverse"

While a foldl is enough to implement a reverse functionality,
adding it as a built in allows doing so in linear time.

1 files changed, 15 insertions, 0 deletions

diff --git a/test/buildtool/build_engine/expression/expression.test.cpp b/test/buildtool/build_engine/expression/expression.test.cpp
index 7f3df7c5..242c0f4a 100644
--- a/test/buildtool/build_engine/expression/expression.test.cpp
+++ b/test/buildtool/build_engine/expression/expression.test.cpp
@@ -942,6 +942,21 @@ TEST_CASE("Expression Evaluation", "[expression]") {  // NOLINT
         )"_json));
     }
 
+    SECTION("reverse expression") {
+        auto expr = Expression::FromJson(R"(
+          { "type": "reverse"
+          , "$1": ["foo", "bar", "baz"]
+          }
+        )"_json);
+        REQUIRE(expr);
+
+        auto result = expr.Evaluate(env, fcts);
+        REQUIRE(result);
+        CHECK(result == Expression::FromJson(R"(
+           ["baz", "bar", "foo"]
+        )"_json));
+    }
+
     SECTION("keys expression") {
         auto expr = Expression::FromJson(R"(
             { "type": "keys"