module NumericPrelude.Text where

{-* Formatting and parsing. -}

{-| Show a value using an infix operator. -}
{-# INLINE showsInfixPrec #-}
showsInfixPrec :: (Show a, Show b) =>
                  String -> Int -> Int -> a -> b -> ShowS
showsInfixPrec opStr opPrec prec x y =
   showParen
     (prec >= opPrec)
     (showsPrec opPrec x . showString " " .
      showString opStr . showString " " .
      showsPrec opPrec y)

{-| Parse a string containing an infix operator. -}
{-# INLINE readsInfixPrec #-}
readsInfixPrec :: (Read a, Read b) =>
                  String -> Int -> Int -> (a -> b -> c) -> ReadS c
readsInfixPrec opStr opPrec prec cons =
   readParen
     (prec >= opPrec)
     ((\s -> [(const . cons, s)]) .>
      readsPrec opPrec .>
      (filter ((opStr==).fst) . lex) .>
      readsPrec opPrec)

{-| Compose two parsers sequentially. -}
infixl 9 .>
(.>) :: ReadS (b->c) -> ReadS b -> ReadS c
(.>) ra rb =
   concatMap (\(f,rest) -> map (\(b, rest') -> (f b, rest')) (rb rest)) . ra