content: -- !!! Array test
  -- This one fails in Hugs (Feb 2001)
  
  module Main where
  
  import Data.Array
  
  -- All in main is only to show the strange behaviour.
  --
  -- arrS is the array that foo (NB (1.0,1)) shows in Hugs.
  -- But (foo (NB (1.0,1)))==arrS is False.
  
  -- If I write NB (f,p) -> hCMt [(p,listArray ((1,1),(1,1)) [f])] instead of line 16
  -- the bug disappears. That is also the reason why I have to keep the data declaration RD.
  -- If I put the type signature of line 18 in scope the bug also disappears.
  -- If I write hCMt po_arL = (accumArray (\a _-> a) ZM ((1,1),(1,2)) []) //
  --                          (map (\(po,ar) -> ((1,po),M ar)) po_arL)
  -- instead of line 19 and 20 it also vanishes.
  
  data CM a = ZM | M (Array (Int,Int) a)  deriving (Show,Eq)
  
  data RD =    NB !(Double,Int)
  
  main  = do
    let arr = foo (NB (1.0,1))
          -- arr = { (1,1) -> M { (1,1) -> 1.0 }, (1,2) -> ZM }
  
          -- All these should return True
    putStr ("arr==arrS "++show (arr==arrS)++"\n")
    putStr ("arrS==arr "++show (arrS==arr)++"\n")
    putStr ("bnds arr arrS "++show ((bounds arr)==(bounds arrS))++"\n")
    putStr ("bnds +id arr arrS "++show (((bounds.id) arr)==((bounds) arrS))++"\n")
    putStr ("id +bnds arr arrS "++show (((id.bounds) arr)==((bounds) arrS))++"\n")
  
  
  foo :: RD -> Array (Int,Int) (CM Double)
  foo rd = case rd of
      NB (f,p) -> h where h = hCMt [(p,listArray ((1,1),(1,1)) [f])]
                          -- h = { (1,p) -> M { (1,1) -> f }, other -> ZM }
     where
     --h0CMt :: Array (Int, Int) (CM Double)
     -- h0CMt = { (1,1) -> ZM, (1,2) -> ZM }
     h0CMt = accumArray (\a _-> a) ZM ((1,1),(1,2)) []
  
     hCMt prs = h0CMt // (map (\(po,ar) -> ((1,po),M ar)) prs)
                          -- [ (1,p), M { (1,1) -> f } ]
  
  
  arrS :: Array (Int,Int) (CM Double)
  arrS = listArray ((1,1),(1,2)) [M (listArray ((1,1),(1,1)) [1.0]),ZM]
  