On 1/24/07, Brian Hulley [EMAIL PROTECTED] wrote:
A possible syntax could represent the
value being matched explicitly, say using ? to represent the value
currently
being matched, then the pattern could be written as an equation:
f (prodSize ? = Small) = ...
f (prodSize ? = Medium) =
-- abstract list deconstructors / list pattern constructors
-- (consP takes h/t sub-patterns as parameters)
consP h t l = do { guard $ not (null l); hr - h (head l); tr - t (tail l);
return (hr,tr) }
nilP l = do { guard $ null l; return () }
-- wildcard and variable patterns
In my opinion, views are going to make more Haskell more complicated, and
from what I have seen so far, for little gain.
Maybe a poll should be made to see what features the average Haskeller feels
the most in need of. Or what their greatest problems are.
Going by the traffic over the previous
There's been lots of interesting feedback about the views proposal -- thank you.
Many of the suggestions amount to plausible design alternatives. If I do all
the editing, I'll just become a bottleneck, and I'm more than usually
snowed-under at the moment. So I've moved the Wiki page to the
| 1 I am a bit concerned about the use of non-linear patterns in your examples.
| There are good arguments for non-linear patterns, and Haskellers have
made good
| arguments against non-linear patterns. But you seem to suggest allowing
non-linear
| patterns in some cases (related to
On Wed, 24 Jan 2007, Claus Reinke wrote:
the alternative I'm aiming for, as exhibited in the consP example, would be
to build patterns systematically from view patterns used as abstract
de-constructors, composed in the same way as one would compose the
abstract constructors to build the
Sorry to enter the discussion a little late ...
First, I'm not clear what Simon meant by first class abstractions
in this comment
Several proposals suggest first class abstractions rather that
first-class patterns. Here are the ones I know of ...
Second, I completely agree with Claus in
On Jan 22, 2007, at 6:57 AM, Simon Peyton-Jones wrote:
I'm thinking of implementing it in GHC, so I'd be interested in
feedback of the form
- how desirable is it to have a feature of this general form?
While it looks like a useful extension with a lot of bang for the buck,
I think
