# [Haskell-cafe] Re: Channel9 Interview: Software Composability and theFu ture of Languages

Kirsten Chevalier catamorphism at gmail.com
Wed Jan 31 10:34:19 EST 2007

On 1/31/07, Bill Wood <william.wood3 at comcast.net> wrote:
> On Wed, 2007-01-31 at 19:51 +1100, Donald Bruce Stewart wrote:
>    . . .
> >     foldl (\water dish -> wash water dish) soapywater dishes :: [Dishes]
>
> Nice example.  First, note that you can't get close with map -- you need
> accumulation across the dishes.  Second, the correctness of this plan
> depends on the rather strong frame axiom that no entity in the
> environment is changed during a step of the fold, so no broken dishes.
> Finally, that doesn't work so well when there are constraints on the
> order that the dishes are washed, for example when washing the cruddiest
> dishes first while there are more suds.
>

It also assumes that there's necessarily a natural decomposition on
the dishes, and if you think there is, you haven't seen my kitchen!

--
Kirsten Chevalier* chevalier at alum.wellesley.edu *Often in error, never in doubt
"Sleeping is a gateway drug / to being awake again" -- They Might Be Giants