[Haskell-cafe] Re: Lambda-case / lambda-if
miguelimo38 at yandex.ru
Thu Oct 7 13:36:53 EDT 2010
Отправлено с iPhone
Oct 7, 2010, в 21:03, Peter Wortmann <scpmw at leeds.ac.uk> написал(а):
> On Tue, 2010-10-05 at 17:10 -0700, Evan Laforge wrote:
>> +1 for something to solve the "dummy <- m; case dummy of" problem.
>> Here are the possibilities I can think of:
> Might be off-topic here, but I have wondered for a while why Haskell
> doesn't support something like follows:
> do case (<- m) of ...
I think it'd be better to write just 'case (<- m) of', without 'do'.
> With the more general rule being:
> do ... e (<- m) g
> ... m >>= \tmp -> e tmp g
> * "<-" is already "sugary", and the transformation is similar. Just
> removes the need for the user to define a throw-away name.
> * Better than liftMX and the Applicative operators. As shown, this is
> more flexible while requiring less magic operators as a bonus. Also
> makes more clear where the sides effects actually are.
> * Goes well with the spirit of getting the good parts of imperative
> coding where it potentially makes the code more concise. Can be
> abused, obviously, but I have also seen a lot of code that I feel
> could be written better using this.
> Anything I am overlooking here? I tried to find a discussion about
> something like this, but didn't really know what to look for...
> Peter Wortmann
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