Add nth builtin

src/builtins.c

@@ -69,6 +69,13 @@ LISP_FUNC_1(ucl_builtin_cdr, state, arg) {
     return ucl_cdr(arg);
 }
 
+LISP_FUNC_2(ucl_builtin_nth, state, n, list) {
+    UCL_COND_OR_RET_ERROR(n->type == UCL_TYPE_INT, "First argument to nth must be an integer");
+    UCL_COND_OR_RET_ERROR(list->type == UCL_TYPE_CELL, "Second argument to nth must be a list");
+
+    return ucl_list_nth(list, n->integer);
+}
+
 LISP_FUNC_2(ucl_builtin_add, state, arg0, arg1) {
     if (arg0->type != UCL_TYPE_INT) {
         return ucl_error_create("Invalid type of argument 0 to 'add'");