[racket] Using syntax/parse, how to accept keyword arguments in any order yet not allow duplicates?

Thanks, that's perfect!  I knew it couldn't have been overlooked :)


On Sun, Apr 7, 2013 at 5:31 PM, J. Ian Johnson <ianj at ccs.neu.edu> wrote:

> The ~in-between pattern and its specializations ~once and ~optional are
> great for this purpose. Anything matching this pattern must appear in the
> range given in ~in-between, even in ellipsis'd contexts.
> (a:id b:id (~or (~once (~seq #:key1 c:id)) (~once (~seq #:key2 d:id))) ...)
>
> -Ian
>
> ----- Original Message -----
> From: "Scott Klarenbach" <scott at pointyhat.ca>
> To: "Racket mailing list" <users at racket-lang.org>
> Sent: Sunday, April 7, 2013 8:23:29 PM GMT -05:00 US/Canada Eastern
> Subject: [racket] Using syntax/parse, how to accept keyword arguments in
> any order yet not allow duplicates?
>
>
>
> Hi there,
>
>
> I'd like to create a macro that accepts non-optional keyword arguments in
> any order. It should however, ensure that all the arguments are provided.
> Finally, it should not allow duplicates.
>
>
> So far I've only been able to solve for my first criteria.
>
>
> As a test, I have this:
>
>
>
> (syntax-parse stx
> [(a:id b:id (~or (~seq #:key1 c:id) (~seq #:key2 d:id)) ...) #t])
>
>
> Now, that matches for:
> #'(a b #:key1 hey #:key2 there)
> #'(a b #:key2 there #:key1 hey)
>
>
>
> Which is what I want. But unfortunately it also matches:
> #'(a b #:key2 there)
>
>
> And worse:
> #'(a b #:key2 one #:key2 two #:key2 three)
>
>
> The reasons are obvious. I'm just wondering if there's a more robust way
> of dealing with these types of scenarios that I'm missing? I thought of
> combining an (~or (~and clause but that becomes very tedious, and leaves
> the duplicate problem unsolved.
>
>
> Thanks.
>
> --
> Talk to you soon,
>
> Scott Klarenbach
>
> PointyHat Software Corp.
> www.pointyhat.ca
> p 604-568-4280
> e scott at pointyhat.ca
> 200-1575 W. Georgia
> Vancouver, BC V6G2V3
>
> _______________________________________
> To iterate is human; to recur, divine
> ____________________
>   Racket Users list:
>   http://lists.racket-lang.org/users
>



-- 
Talk to you soon,

Scott Klarenbach

PointyHat Software Corp.
www.pointyhat.ca
p 604-568-4280
e scott at pointyhat.ca
200-1575 W. Georgia
Vancouver, BC V6G2V3

_______________________________________
To iterate is human; to recur, divine
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