On Tue, Mar 13, 2001 at 09:40:09 +0200, Matthias Fischmann wrote:
> Yes, that does not look very nice but it should work. In a private
> response, I was also pointed out the alternative solution of using
> case together with `seq` to trigger evaluation, which looked like the
> default way to me (what else is seq for?):
suppose sth. like:
foo someRecord = do
...
foo someRecord{ field = field' }
this may lead to quite some memory allocation (I had this case once,
IIRC), and eventually it can be reduced by using `seq`:
foo someRecord = do
...
let r = someRecord{ field = field' }
r `seq` foo r
>
> | case monstrousDS `seq` True of True -> hPutStr stderr "ok."
*hmm* this just evaluates to WHNF, no?
>From hugs:
Prelude> case (42,error "foo") `seq` True of True -> putStrLn "yow"
yow
> I first tried to wrap this in a `force' function, thereby proving that
> I still haven't grasped the concept entirely. (-:
forceEval x = if x == x then x else x
but this *still* needs a decent equality on `x'... 8->
> But maybe it is possible to make a primitive of this in the same way
> as has been done with assert?
This would definitely help to e.g. keep exceptions inside
`catch'-blocks sometimes (of course at the expense of not being able
to use infinite data structures at the same time there)...
Cheers,
Michael
--
/~\ ASCII ribbon | "I would rather spend 10 hours reading someone else's
\ / campaign | source code than 10 minutes listening to Musak waiting
X against | for technical support which isn't."
/ \ HTML mail | -- Dr. Greg Wettstein, Roger Maris Cancer Center
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