rearrange builtins

builtins/last.go

@@ -0,0 +1,23 @@
+package builtins
+
+import "monkey/object"
+
+// Last ...
+func Last(args ...object.Object) object.Object {
+	if len(args) != 1 {
+		return newError("wrong number of arguments. got=%d, want=1",
+			len(args))
+	}
+	if args[0].Type() != object.ARRAY_OBJ {
+		return newError("argument to `last` must be array, got %s",
+			args[0].Type())
+	}
+
+	arr := args[0].(*object.Array)
+	length := len(arr.Elements)
+	if length > 0 {
+		return arr.Elements[length-1]
+	}
+
+	return nil
+}