> Depends on the application. Consider for example a browser in which
> when you hit the 'back' button, you want to go back to the same
> state as previously: with purely functional data structures attached
> to a state object, going back is a simple matter of popping the state
> object from a stack (and re-rendering :-)
> 
> This is not so easy to do with a more extensively mutable state object.

There was a paper on just this topic in this year's ICFP.  Check out:

The Influence of Browsers on Evaluators
http://youpou.lip6.fr/queinnec/Papers/webcont.ps.gz

Mike

-- 
Michael Hicks
Ph.D. Candidate, the University of Pennsylvania
http://www.cis.upenn.edu/~mwh            mailto://mwh@dsl.cis.upenn.edu
*There was a man who entered a local paper's pun contest; He sent in ten
*different puns, in the hope that at least one of the puns would win.  
*Unfortunately, no pun in ten did.