Hello! I think it's better that the ghc can read what is printed by pretty printer. Now: pprLit 0 (RationalL 3.5) => 7 % 2 I want: pprLit 0 (RationalL 3.5) => 7 / 2 I'll send patch --- pprLit i (RationalL rat) = parensIf (i > noPrec) $ integer (numerator rat) <+> char '/' <+> integer (denominator rat)