Module S.Formula
val hash : t -> intHashing function for formulas. Should be such that two formulas equal according to
Expr_intf.S.equal have the same hash.
val pp : t Solver_intf.printerPrinting function used among other thing for debugging.
val norm : t -> t * Solver_intf.negatedReturns a 'normalized' form of the formula, possibly negated (in which case return
Negated).normmust be so thataandneg anormalise to the same formula, but one returnsNegatedand the otherSame_sign.