[Haskell-cafe] lambda case (was Re: A big hurray for lambda-case (and all the other good stuff))

Andreas Abel andreas.abel at ifi.lmu.de
Fri Nov 30 04:02:41 CET 2012

I had been missing a pattern matching lambda in Haskell for a long time 
(SML had "fn" since ages) and my typical use will be

   monadic_expr >>= \case

I think "\case" is not the worst choice, certainly better than "of" ...

Thanks to the GHC 7.6 developers!


On 29.11.12 12:49 PM, Jon Fairbairn wrote:
> Ben Franksen <ben.franksen at online.de> writes:
>> just wanted to drop by to say how much I like the new lambda case extension.
>> I use it all the time and I just *love* how it relieves me from conjuring up
>> dummy variables, which makes teh code not only esier to write but also to
>> read.
>> […] should *definitely* go into Haskell'13.
> As I was opposed to the suggestion for lambda case I didn’t
> really follow the discussion of the syntax, but I’m puzzled by
> the choice. To me it seems obvious that if we are going to do
> this (as opposed to something more decomposable like
> lambda-match), we should do it simply by making the “case exp”
> part of a case expression optional. So the syntax for lambda-
> case would be
>     of {alts…}
> and we would then describe
>     case e of {…}
> as syntactic sugar for
>     (of {…}) (e)
> Doing it this way doesn’t introduce any new syntactic elements
> and has fewer tokens at the point of use.
> I don’t see any need for a \ in the syntax: this is a functional
> language we are talking about after all. Once we know that “of”
> introduces a function, that should be enough.

Andreas Abel  <><      Du bist der geliebte Mensch.

Theoretical Computer Science, University of Munich
Oettingenstr. 67, D-80538 Munich, GERMANY

andreas.abel at ifi.lmu.de

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