{-# OPTIONS_GHC -farrows #-}

{---

  Code for displaying Boolean signals for use with circuits.

  Taken from Programming with Arrows by John Hughes.

---}
module Signal where

import qualified Data.List as L

class Signal a where
    showSig :: [a] -> String

instance Signal Bool where
    showSig bs = concat top++"\n"++concat bot++"\n" where
        (top, bot) = unzip $ zipWith sh (False:bs) bs
        sh True True = ("__", "  ")
        sh True False = ("  ", "|_")
        sh False True = (" _", "| ")
        sh False False = ("  ", "__")

instance (Signal a, Signal b) => Signal (a, b) where
    showSig xys = showSig (map fst xys) ++ showSig (map snd xys)

instance Signal a => Signal [a] where
    showSig = concat . map showSig . (L.transpose)

sig = concat . map (uncurry replicate)

testSig = sig
  [(5,(False,False)), (2,(False,True)), (5,(False,False)), (2,(True,False)), (5,(False,False)), (2,(True,True)), (6,(False,False))]