--
-- Adapted from the program "infer", believed to have been originally
-- authored by Philip Wadler, and used in the nofib benchmark suite
-- since at least the late 90s.
--
module Shows
(Shows, showsEmpty, showsConcat, showsString, showsChar, showsStar,
showsStarSep, showsSurround, showsListOf, showsParen, showsParenIf)
where
type Shows x = x -> ShowS
showsEmpty :: ShowS
showsEmpty r = r
showsConcat :: [ShowS] -> ShowS
showsConcat = foldr (.) showsEmpty
showsString :: Shows String
showsString = (++)
showsChar :: Shows Char
showsChar = (:)
showsStar :: Shows x -> Shows [x]
showsStar showsX xs = showsConcat (map showsX xs)
showsStarSep :: String -> Shows x -> Shows [x]
showsStarSep s showsX [] = showsEmpty
showsStarSep s showsX (x:xs) = showsX x
. showsConcat [showString s . showsX x' | x' <- xs]
showsSurround :: String -> Shows x -> String -> Shows x
showsSurround l showsX r x = showString l . showsX x . showString r
showsListOf :: Shows x -> Shows [x]
showsListOf showsX = showsSurround "[" (showsStarSep ", " showsX) "]"
showsParen :: ShowS -> ShowS
showsParen = showsSurround "(" id ")"
showsParenIf :: Bool -> ShowS -> ShowS
showsParenIf b xS = if b then showsParen xS else xS