[racket] match in Advanced Student?

Are you referring to the special case on line 2730 of teach.rkt when
you say posns?

I think that means that I'd have to make the teaching language depend
on 2htdp/image, which doesn't seem right.

I would have thought that the right thing would be to extend the
define-primitive protocol so that I can declare that 'color' is both a
function and a struct constructor and then match would not have to
special case 'color'. No?

Robby

On Mon, Oct 31, 2011 at 9:48 PM, Jay McCarthy <jay.mccarthy at gmail.com> wrote:
> The HtDP match implementation has a list of such things and goes and
> finds them to turn them back into the non-primitive bound things.
> That's why it works with posns.
>
> Something better could be done, but for now you could add it to the white list.
>
> Jay
>
> On Mon, Oct 31, 2011 at 8:45 PM, Robby Findler
> <robby at eecs.northwestern.edu> wrote:
>> Oh, I see why. 'color' is bound using define-primitive in order to
>> cooperate with the beginner language (and so that 'color' can be a
>> constructor). But doing that interferes with the usual information
>> bound by a struct that match picks up.
>>
>> I'm not sure what the right way to resolve this is.
>>
>> Robby
>>
>> On Mon, Oct 31, 2011 at 9:39 PM, Robby Findler
>> <robby at eecs.northwestern.edu> wrote:
>>> Is make-color coming from 2htdp/image? I see that's not working (not
>>> sure why yet).
>>>
>>> Robby
>>>
>>> On Mon, Oct 31, 2011 at 9:34 PM, Adam Shaw <adamshaw at cs.uchicago.edu> wrote:
>>>> Thanks! That still doesn't work for color:
>>>>   match: color does not refer to a structure definition
>>>> although it does work with my own custom color struct:
>>>> (define-struct clr (r g b))
>>>> (match (make-clr 1 2 3)
>>>>   [(struct clr (r g b)) (* r g b)])
>>>>   - Adam
>>>> On Oct 31, 2011, at 9:26 PM, Jay McCarthy wrote:
>>>>
>>>> One of the branches of the pattern language is
>>>>
>>>> | (struct id (pattern ...))
>>>>
>>>> Your pattern should be
>>>>
>>>> (struct color (r g b))
>>>>
>>>>
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>>>
>>
>
>
>
> --
> Jay McCarthy <jay at cs.byu.edu>
> Assistant Professor / Brigham Young University
> http://faculty.cs.byu.edu/~jay
>
> "The glory of God is Intelligence" - D&C 93
>