On Sun, Oct 08, 2006 at 10:57:46PM +1300, [EMAIL PROTECTED] wrote: > To: haskell-cafe@haskell.org > From: [EMAIL PROTECTED] > Date: Sun, 08 Oct 2006 22:57:46 +1300 > Subject: [Haskell-cafe] collection monads > > Matthias Fischmann wrote: > > > Do you expect the contained type x to change during a > > > sequence of monadic actions? e.g. would you ever use > (>>=) > > > at the type 'Permutation Int -> (Int -> Permutation > Bool) -> > > > Permutation Bool'? > > > > no, i don't need that. but aside from > > the fact that > > > > > data Permutation k v = > > > Permutation [(k, v)] > > > instance (Ix k) => > > > Monad (Permutation k) > > > > is redundant (i think of the permutation > > as a function applicable to arbitrary > > lists): how would that change anything? > > my definition of return still doesn't > > work. or how would you redefine > > 'return'? > > Ah. Yes, my approach falls over because it lacks two > things. #1: a distinguished value of the Ix-constrained > type k, to pair off with return's argument. #2: a purpose. > I don't have a clear idea of what a do-block in a > permutation monad ought to mean. Whoops! <font > color=red>:-]</font>
yes, me neither. i thought of something like sequencial execution of permutations, and was hoping it was similar enough to strings and concat / join. but it seems it's something else... ok, permutations are not that monadic, really. i'll try to live with it. (-: matthias
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