CaseOfCase.hs

module CaseOfCase (f2) where

data What = Int Int | TT | FF

{-# inline f1 #-}
f1 :: Word -> What
f1 x = case x of
  1 -> Int 1
  2 -> TT
  3 -> FF

f2 :: Word -> IO ()
f2 x = case f1 x of
  Int i -> print i
  TT -> print True
  FF -> print False

-- inline f1

f2_2 x = case (case x of
  1 -> Int 1
  2 -> TT
  3 -> FF) of
  Int i -> print i
  TT -> print True
  FF -> print False

-- case-of-case

f2_3 x = case x of
  1 -> case Int 1 of
    Int i -> print i
    TT -> print True
    FF -> print False
  2 -> case TT of
    Int i -> print i
    TT -> print True
    FF -> print False
  3 -> case FF of
    Int i -> print i
    TT -> print True
    FF -> print False

-- case of known constructor

f2_4 x = case x of
  1 -> print 1
  2 -> print True
  3 -> print False