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" <ro...@eecs.northwestern.edu <javascript:;>>
To: "Sam Tobin-Hochstadt" <sa...@ccs.neu.edu <javascript:;>>
Cc: dev@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
< ro...@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
>> < ro...@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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