array builtins

builtins/reversed.go

@@ -0,0 +1,20 @@
+package builtins
+
+import (
+	"monkey/object"
+)
+
+// Reversed ...
+func Reversed(args ...object.Object) object.Object {
+	if len(args) != 1 {
+		return newError("wrong number of arguments. got=%d, want=1",
+			len(args))
+	}
+
+	if a, ok := args[0].(*object.Array); ok {
+		newArray := a.Copy()
+		newArray.Reverse()
+		return newArray
+	}
+	return newError("argument #1 to `reversed` expected to be `array` got=%T", args[0].Type())
+}