[racket] Pattern matching define macro

By the way I’m just wondering: 

Is there any reason why you can’t just use match-patterns instead of using ($ match-pattern) ?

And is there anything like a “generic-binding-expander” that would act sort of like a match-expander?

And is there some kind of "generic-bind/renamed” module or something that provides everything from generic-bind except without the ~ in front?


On Jul 15, 2014, at 3:02 PM, Stephen Chang <stchang at ccs.neu.edu> wrote:

>> I just found this, which has a lot of forms for just about everything I can think of (and more) that support things like match-patterns:
>> https://github.com/stchang/generic-bind
>> 
>> I haven’t tried it yet, but It looks pretty amazing.
>> 
>> It probably has everything you want.
> 
> Thanks for the kind words. :)
> 
> This was an experiment that tried to address a few questions that
> repeatedly get asked on the mailing list:
> 
> 1) that you can't destructure data structures at the binding site, and
> 2) that you need to manually define many different versions of each
> binding construct (eg define, match-define, match-define-values, etc),
> which inevitably means that some binding forms don't exist (eg
> match-for/X forms)
> 
> Something like the expressivity problem for binding forms.
> 
> I tried to implement one "generic" version of each binding form that
> would accept many different "binding instances", so every binding form
> would be extensible by implementing the appropriate instance (eg, a
> matching instance, a values instance)
> 
> Every Racket binding form should have a ~-prefixed version in my
> library and my version should work as a drop-in replacement for its
> Racket counterpart if you want to try it out.
> 
> Here's a link to the docs if you're interested in reading more:
> http://stchang.github.io/generic-bind/generic-bind.html
> 
> (You can tell that it hasn't been updated in a while from the old css.)
> 
> Caveat: my macro-fu hasn't quite reached expert level so I'd love for
> anyone to tell me where my code is bad.
> 
> That being said, I ran a large part of the Racket test suite using my
> binding forms instead of the Racket ones so they should be usable in
> most scenarios.
> 
> 
> 
> 
> 
> 
> 
>> 
>> On Jul 13, 2014, at 12:41 AM, Alexander D. Knauth <alexander at knauth.org> wrote:
>> 
>>> 
>>> On Jul 12, 2014, at 10:17 PM, Alexander D. Knauth <alexander at knauth.org> wrote:
>>> 
>>>> 
>>>> On Jul 12, 2014, at 6:43 PM, Brian Adkins <racketusers at lojic.com> wrote:
>>>> 
>>>>> I probably won't keep my defpat macro, at least not in its present form (for one, it only handles a single arg); there's probably a balance between being concise and being general/flexible.
>>>> 
>>>> Although define/match is definitely more powerful, if you want it, this would probably be a good version of what you want that would handle multiple arguments:  (I’ll reply again if I get one to work with optional and/or keyword-arguments)
>>>> (define-syntax defpat
>>>> (syntax-rules ()
>>>>  [(defpat (f arg-pat ...) body ...)
>>>>   (defpat f (match-lambda** [(arg-pat ...) body ...]))]
>>>>  [(defpat id expr)
>>>>   (define id expr)]))
>>> 
>>> Ok I just made a version of defpat that can handle multiple arguments, optional arguments, keyword-arguments, and optional keyword-arguments.
>>> I also made a form called my-match-lambda that defpat uses to do this.
>>> https://github.com/AlexKnauth/defpat
>>> Also to do this I had to make it so that you have to use square brackets to specify optional arguments, otherwise it couldn’t tell between an optional argument and a match pattern.
>>> 
>> 
>> 
>> ____________________
>>  Racket Users list:
>>  http://lists.racket-lang.org/users