toFormula (Atom (Eq l r))          = join $ Z.mkEq <$> toExpression l <*> toExpression r
toFormula (Atom (Eq l r))          = join $ Z.mkEq <$> toExpression l <*> toExpression r
toFormula (Atom (Eq l r))          = join $ Z.mkEq <$> toExpression l <*> toExpression r