Re: comonads, io

2 Jan 2003


      In article <20030102225641.GA24187@smtp.alicorna.com>,
 Andrew J Bromage  wrote:
...
comain :: OI a -> ()
  comain w
      = coeval (w .>> show (a,b) =>> stdPutStrLn)
      where
      a = coeval (w .>> () =>> stdGetChar)
      b = coeval (w .>> () =>> stdGetChar)
Even though a and b are identical, they return different values.  I see
two possibilities: Either my intuition is way off, or the OI comonad
breaks referential transparency.
So is Kieburtz smoking crack, or are we writing OI-style programs 
incorrectly? One possibility is that comonads are useful for some 
things, but not for doing IO actions safely.

-- 
Ashley Yakeley, Seattle WA