sig
type formula =
LNext of Ltlast.formula
| LUntil of Ltlast.formula * Ltlast.formula
| LFatally of Ltlast.formula
| LGlobally of Ltlast.formula
| LRelease of Ltlast.formula * Ltlast.formula
| LNot of Ltlast.formula
| LAnd of Ltlast.formula * Ltlast.formula
| LOr of Ltlast.formula * Ltlast.formula
| LImplies of Ltlast.formula * Ltlast.formula
| LIff of Ltlast.formula * Ltlast.formula
| LTrue
| LFalse
| LCall of string
| LReturn of string
| LCallOrReturn of string
| LIdent of string
end