| Dot of avar * path
| Ex of avar list * query
| Select of avar * query * query
- | Let of svar * query * query
+ | Let of svar option * query * query
| Fun of path * path list * query list
| Gen of path * query list
| Add of bool * groups * query
| For of gen * avar * query * query
+ | While of gen * query * query
| Property of inverse * refine * path *
main * istrue * isfalse list * exp_list *
pattern * query