S.Formulaformulas
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 Msat.Solver_intf.printerPrinting function used among other thing for debugging.
val norm : t -> t * Msat.Solver_intf.negatedReturns a 'normalized' form of the formula, possibly negated (in which case return Negated). norm must be so that a and neg a normalise to the same formula, but one returns Negated and the other Same_sign.