On 06/10/2010 00:04, Max Bolingbroke wrote:
On 5 October 2010 17:38, Henning Thielemann
<schlepp...@henning-thielemann.de> wrote:
Richard O'Keefe schrieb:
I'd prefer to see something like
\ 1 -> f
| 2 -> g
but I'm sure something could be worked out.
In order to be consistent with current case, maybe in layout mode:
\1 -> f
2 -> g
and in non-layout mode
\{1 -> f; 2 -> g}
Duncan Coutts also suggested this possibility to me - once I saw it
actually liked it rather better than the lambda-case stuff,
particularly since it generalises nicely to multiple arguments. I may
try to write a patch for this extension instead when I get some free
time.
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.
The motivation for this syntax is:
* easy to mentally parse: \ still introduces a function.
(better than 'case of' in this respect)
* 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)
Cheers,
Simon
_______________________________________________
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
