[Haskell-beginners] Global variable question
velman at cox.net
Thu Dec 31 18:38:00 EST 2009
On Thu, Dec 31, 2009 at 09:37:10AM -0800, Joe Van Dyk wrote:
> On Wed, Dec 30, 2009 at 6:05 PM, Edward Z. Yang <ezyang at mit.edu> wrote:
> > Excerpts from Joe Van Dyk's message of Wed Dec 30 20:49:12 -0500 2009:
> >> What's the appropriate way to write this in Haskell?
> > Hi Joe,
> > The Ticker class is an example of stateful computation, which we try
> > to avoid in Haskell. What are you really trying to do?
> > * If you a number, and you want to add to it, (+1) works
> > plenty well.
> > * If you are going to be making ticks, but you don't care about
> > reading the ticks until the end of the computation, the Writer monad
> > is of interest.
> > * If you need to update the tick count and read it, the State
> > monad is a good bet.
> > * If you're interested in curiosities from imperative land, STRef, IORef and
> > other similar creatures may be helpful.
> It's like haskell is on a personal vendetta against me to make me feel dumb.
It's not personal.
> Joe Van Dyk
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