Re: [Haskell-beginners] How to construct complex string

9 Aug 2013

      On Sat, Aug 10, 2013 at 12:41 AM, martin  wrote:
...
...
instance Monad Dot where
  return a = Dot $ \ uq -> ([],uq,a)
  m >>= k  = Dot $ \ uq -> case unDot m uq of
               (g1,uq',r) -> case unDot (k r) uq' of
                       (g2,uq2,r2) -> (g1 ++ g2,uq2,r2)
I tried to rewrite this using "where" and was bitten badly, because
inside the "where" uq would not be defined.
You could write:

m >>= k = Dot f  where
   f uq = (g1 ++ g2, uq2, r2)  where
      (g1, uq', r) = unDot m uq
      (g2, uq2, r2) = unDot (k r) uq'

Doubtless, there has to be a way of revealing the inner structure, which
looks like some state monad with icing on top.

-- Kim-Ee

Re: [Haskell-beginners] How to construct complex string

Kim-Ee Yeoh