On Friday 03 September 2010 12:28:43, Jan Christiansen wrote:
> Hi,
>
> On 03.09.2010, at 01:32, Daniel Fischer wrote:
> > No surprise, there aren't many 'รค's in Shakespeare's works, are there?
>
> nope
>
> > On the other hand, the current implementation of lines does not seem
> > to
> > suffer from Wadler's tuple space leak (according to one test I
> > made), so
> > I'd stick with the current implementation for the time being.
>
> Well, I think it does.
Indeed. I botched my test, allowing it to drop the reference to the first
line too early by not using enough of it, so although lines shows the leak,
let {
ds1_s1ts :: ([Char], [Char])
LclId
ds1_s1ts =
case $wbreak @ Char lvl_r1uj wild_B1
of _ { (# ww1_anp, ww2_anq #) ->
(ww1_anp, ww2_anq)
} } in
:
@ String
(case ds1_s1ts of _ { (l_aij, _) -> l_aij })
(case ds1_s1ts of _ { (_, s'_ail) ->
case s'_ail of _ {
, I managed to conceal it.
> But obviously one can argue that this is a rare application.
Yes. Ordinarily, lines in text files aren't longer than a few hundred
characters, leaking those, who cares?
But. Occasionally, long lines occur, and avoiding the space leak seems more
important to me than having
lines (_|_ : _|_) = _|_ : _|_
instead of
lines (_|_ : _|_) = _|_
> Hopefully I haven't made a mistake here?
No.
>
> By accident I stumbled across an odd behaviour. If I use the following
> definition and replace all occurrences of break by break' in the
> program above the memory behaviour is bad if I compile it without
> profiling. But if I compile the program with -prof -auto-all the
> program runs in constant space. Is this a known behaviour?
I can't reproduce that. For me, it leaks also with profiling.
>
> break' :: (a -> Bool) -> [a] -> ([a],[a])
> break' p xs = (ys,zs)
> where
> (ys,zs) = break p xs
>
> Cheers, Jan
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