On Friday, May 3, 2013, Ryan Culpepper wrote: > 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.) > > I would not midn if that bound 'else' as a variable.
The only change I'd request is that when 'else' is the entire pattern, since that's the situation that's confusing to people not language lawyers. Robby > 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 >> >> _________________________ >> Racket Developers list: >> http://lists.racket-lang.org/**dev <http://lists.racket-lang.org/dev> >> >> >> >> _________________________ >> Racket Developers list: >> http://lists.racket-lang.org/**dev <http://lists.racket-lang.org/dev> >> >> >
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