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

(that was assuming Ryan's assertion that "[...]Matthew say that he would
have used a keyword for `else` in `cond` if he had it to do over again",
which seem to mean that even in Racket2 Matthew would prefer `#:else' over
`[else ...]' ?)


On Sat, May 4, 2013 at 5:14 PM, Laurent <laurent.orseau at gmail.com> wrote:

> Matthew,
> Out of curiosity, could you explain why you'd prefer #:else everywhere
> instead of [else ...] ?
> Would such an #:else allow for multi-line bodies?
>
>
> On Sat, May 4, 2013 at 5:06 PM, Matthew Flatt <mflatt at cs.utah.edu> wrote:
>
>> At Sat, 4 May 2013 09:15:22 -0500, Robby Findler wrote:
>> > On Sat, May 4, 2013 at 9:07 AM, Matthew Flatt <mflatt at cs.utah.edu>
>> wrote:
>> >
>> > > At Fri, 3 May 2013 17:29:52 -0400, Eli Barzilay wrote:
>> > > > A few minutes ago, Robby Findler wrote:
>> > > > >
>> > > > > FWIW, this was the bug in redex that prompted me to send this
>> > > > > message (it was there for some time since it wasn't a syntax error
>> > > > > .... it was similar in spirit to the code I posted; things broke
>> > > > > when #f was an argument)
>> > > >
>> > > > [I think that it's good to have a much more relaxed policy about
>> > > > breaking compatibility in cases like this: so far there was no real
>> > > > code found that uses the feature, but there is one instance of code
>> > > > that would get fixed by the change...]
>> > >
>> > > Well, Ian provided an example from real code, right? Ian is willing to
>> > > change his code, but the code sounds real.
>> > >
>> > > There's also the use in `unparse-pattern' in Redex. Maybe that's the
>> > > troublesome one that Robby has in mind changing (or he would be happy
>> > > to change it, obviously), but it's another real example.
>> > >
>> > >
>> > No, that was not the example. The code I sent at the beginning of the
>> > thread was an adjusted version of the bug that hid in Redex for,
>> roughly,
>> > months. It was a real bug and caused real problems and we knew something
>> > was wrong but didn't find it for some time.
>> >
>> > In other words, this isn't some made-up, code cleanliness-based request.
>>
>> Yes, I understand that you faced a real bug. I hedged above on
>> `unparse-pattern' not to suggest that your actual bug was
>> uninteresting, but to suggest that I might misunderstand the
>> relationship between the bug and the current state of our repository.
>>
>> All else being equal, I'm definitely in favor of a change to a sensible
>> `else' for `match'. The "else" that isn't equal, however, is backward
>> compatibility, and I think we're at the right point in our development
>> cycle to defer backward incompatibilities to the next language ---
>> hence my vote to defer.
>>
>> _________________________
>>   Racket Developers list:
>>   http://lists.racket-lang.org/dev
>>
>
>
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