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._______________________________________________
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