[Haskell-cafe] Parse text difficulty

Conor McBride ctm at cs.nott.ac.uk
Thu Dec 9 20:04:03 EST 2004

Tomasz Zielonka wrote:
 > On Thu, Dec 09, 2004 at 05:55:09PM +0000, Conor McBride wrote:
 >>Funny you should choose that word:
 >>  http://www.mail-archive.com/haskell@haskell.org/msg15073.html
 >>saves me banging the same old drum.
 > Is ap alias <# alias <%> for [] really the same as zwApply? Probably
 > I am missing something.

Yes and no. Depends which list monad you're using. zwApply is the <%>
of one of the list idioms: it corresponds to the 'vectorizing' list monad
whose return is repeat and whose join computes the diagonal of a matrix.
But you're right: library ap for the 'list of successes' monad and zwApply
do not coincide. I tend to use different list functors, depending on what
they're for, so that all the plumbing is correctly cued from the types.




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