[racket-dev] else clauses: possible change to match?

On 05/03/2013 11:12 AM, Robby Findler wrote:
> Can you point to some examples?
>
> Note that you can still use else, as long as you don't refer to it as a
> variable.

Just to check: If match treats else specially, it should only accept it 
as the entire pattern. For example, the following should be an illegal 
use of else:

   (match x [(list 'if test then else) ___])

Right?

(BTW, I may have written exactly the code above. I need to check.)

Ryan


> On Friday, May 3, 2013, J. Ian Johnson wrote:
>
>     I've used else as a catch-all binding in match. Yes, it's not the
>     best practice, but I think since I've done it, other people must
>     have done it too. This could annoy them.
>     -Ian
>     ----- Original Message -----
>     From: "Robby Findler" <robby at eecs.northwestern.edu <javascript:;>>
>     To: "Sam Tobin-Hochstadt" <samth at ccs.neu.edu <javascript:;>>
>     Cc: dev at racket-lang.org <javascript:;>
>     Sent: Friday, May 3, 2013 11:04:27 AM GMT -05:00 US/Canada Eastern
>     Subject: Re: [racket-dev] else clauses: possible change to match?
>
>
>     Given that we don't yet even have a prototype of racket2, I'm going
>     to guess that "near" isn't all that near. IMO, there are other big
>     things that we should be focused on going first (notably the package
>     system).
>
>
>     Just to check again: Is no one concerned with the backwards
>     incompatibility issue?
>
>
>
>     Robby
>
>     On Friday, May 3, 2013, Sam Tobin-Hochstadt wrote:
>
>
>     Right, I agree with this. My question is basically: are we going to,
>     in the reasonably near future, be encouraging people to program in a
>     `#lang racket2` where `cond` works differently, in which case it
>     doesn't seem worth it to change `match`. Otherwise, I'll do this now.
>
>     Sam
>
>     On Fri, May 3, 2013 at 10:42 AM, Robby Findler
>     < robby at eecs.northwestern.edu <javascript:;> > wrote:
>      > Cond's else cannot change. I agree that that's what I would
>     change if I
>      > could have it back to do it over, but we cannot.
>      >
>      > That's the way to perhaps be thinking about racket2, tho.
>      >
>      > Robby
>      >
>      >
>      > On Friday, May 3, 2013, Sam Tobin-Hochstadt wrote:
>      >>
>      >> On Fri, May 3, 2013 at 10:22 AM, Robby Findler
>      >> < robby at eecs.northwestern.edu <javascript:;> > wrote:
>      >> >
>      >> > For this kind of thing, my preference would be to change match
>     than to
>      >> > issue
>      >> > a warning. I don't like warnings that are basically admitting
>     weaknesses
>      >> > in
>      >> > the language design.... Of course, changing a core thing like
>     that may
>      >> > be
>      >> > more trouble than it is worth, due to backwards compatibility
>     concerns,
>      >> > which is why I think it is worth raising here to see what
>     others think.
>      >>
>      >> I'm happy to make this change to `match`, except that I've heard
>      >> Matthew say that he would have used a keyword for `else` in
>     `cond` if
>      >> he had it to do over again, and I wouldn't want to change one
>     way, and
>      >> then change back.
>      >>
>      >> Sam
>
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