[Haskell-cafe] Re: Functional programming for processing oflargeraster images

[voigt.16734551 at bloglines.com]

--- Matthias Fischmann <fis at wiwi.hu-berlin.de wrote:

> On Thu, Jun 22,
2006 at 09:22:34AM +0100, Simon Peyton-Jones wrote:
> > To: Brian Hulley
<brianh at metamilk.com>, Joel Reymont <joelr1 at gmail.com>
> > Cc: haskell-cafe at haskell.org

> > From: Simon Peyton-Jones <simonpj at microsoft.com>
> > Date: Thu, 22 Jun
2006 09:22:34 +0100
> > Subject: RE: [Haskell-cafe] Re: Functional programming
for processing
> > 	oflargeraster images
> > 
> > http://haskell.galois.com/cgi-bin/haskell-prime/trac.cgi/wiki/BangPatterns

> > 
> > Bang patterns make it much more convenient to write a strict function.

> > E.g
> > 	f (x, !y) = ...
> > is strict both in the pair (of course)
but also in the second component
> > of the pair, y.
> 
> i am ecstatic
to hear that :).

Well, you shouldn't be too enthusiastic, but rather follow
the above link ...
 
> if it really means that 'y' will be fully evaluated
(not top level
> normal form, but whatsthenameforthis, in the way ocaml evaluates

> expressions), it's something i have been missing so much that i was
>
thinking of switching back to a strict language again.

... to find out
that that's exactly not what bang patterns will do for you. They are compiled
into uses of seq, which means evaluation to weak head normal form.

Ciao,
Janis.