[racket-dev] Providing macro definitions for BSL programs

Ah, thank you. Now, how about this definition:

(define-syntax (my-macro stx)
  (syntax-case stx (->)
    [(_ (func arg ...) -> rslt)
     #`(length (cons func (list arg ...)))]))
(provide my-macro ->)

i.e. my macro takes the function name, bundles in up in a structure
(here I just used "cons") and then maybe passes it off to something
else for processing (here I just used "length" for illustration).

Now, doing something like this in the BSL file:
   (my-macro (reward 3) -> "bronze")

produces:
  reward: this is a procedure, so it must be applied to arguments
(which requires using a parenthesis before the name)





On Sat, Sep 4, 2010 at 4:42 PM, Matthias Felleisen <matthias at ccs.neu.edu> wrote:
>
> You need to define and export -> . Otherwise students don't have access to the specific -> in your macro.
>
> BTW, injecting macros into *sl languages demands a lot of error checking because novices are easily confused.
>
>
>
>
> On Sep 4, 2010, at 4:37 PM, Nadeem Abdul Hamid wrote:
>
>> Suppose I make a "teachpack" that defines a macro:
>>
>> #lang racket
>> ...
>> (define-syntax (my-macro stx)
>>  (syntax-case stx (->)
>>    [(_ (func arg ...) -> rslt)
>>     #`(check-expect (func arg ...) rslt)]))
>> (my-macro (+ 4 5) -> 10)
>> (test)
>> (provide my-macro)
>>
>> Running this file works fine.
>>
>> Now, how exactly do I make this macro available to programs written in
>> Beginning/Intermediate Student? Opening up a file in BSL level and
>> typing:
>>  (require "my-macro.rkt")
>>  (my-macro (+ 4 5) -> 9)
>> gives the error:
>>  my-macro: bad syntax
>>
>> This macro is a simplification of the real thing I'm working on, but
>> note that the arguments to this macro include name(s) of functions
>> defined in the BSL file. I though of maybe using
>> provide-higher-order-primitive, but it doesn't seem to work either.
>>
>> --- nadeem
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>
>