l → String → String
showParensIf p s = if p then "(" ++ s ++ ")"
                   else s

sepAndParen ∷ Bool → [
showParensIf ∷ Bool → String → String
showParensIf p s = if p then "(" ++ s ++ ")"
                   else s
showParensIf p s = if p then "(" ++ s ++ ")"
                   else s