At 4:43 PM -0400 10/6/10, Sterling Clover wrote:
On Oct 6, 2010, at 5:39 AM, Simon Marlow wrote:
A slightly different suggestion from Simon PJ and myself (we
agreed on something syntax-related :-) is the following:
\case 1 -> f
2 -> g
where the two-token sequence '\ case' introduces a new optional
layout context, the body of which is exactly the same as in a case
expression. So you could also write
\case { 1 -> f; 2 -> g }
if you want. Guards are allowed of course.
* a bit more noisy than just \: I'm not sure what the
ramifications of having \ introduce a layout context
on its own would be, but I suspect there would be difficulties.
Certainly some existing code would fail to parse, e.g.
(case e of [] -> \x -> x+1; (x:xs) -> \x -> x+2)
\ introducing a layout context is a no-go because, as in the example
given, it breaks too much code. However, \case as described is
somewhat less powerful. In particular, \ with a layout context lets
us have multi-argument pattern matching, while both \case and "case
of" give only single argument pattern matching. I don't know if the
extra functionality is that important, but I don't see why we can't
provide for it anyway, as in:
\case (x:xs) n -> go xs; _ n -> n;
Cheers,
Sterl._______________________________________________
I would also very much like to have multi-argument pattern matching, but in
\case a b -> ...
...
it sure suggests to me that `a` should be applied to `b` before casing.
Dean
_______________________________________________
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
