Thanks for your help Alexander. I did have this much working alright in a
different manner. What I guess I wanted was that this syntax was introduced
per struct so that the same syntax worked for all interface-structs. That
is, if I
(interface-struct test (a b c)
[(define (some-interface-function ...))
...]) =>
(struct test (a b c)
#:methods gen:???
[(define-struct-fields (field:id ...) ...)
(define (some-interface-function ...) ...) ...])
Essentially all it had to do was grab the struct name automatically, just
one more level of indirection. It seemed straightforward but in my example
code the methods defined for the generic interface were not seen.
Deren
On Tue, Aug 18, 2015 at 12:07 AM, Alexander D. Knauth <alexan...@knauth.org>
wrote:
> Are you looking for a macro like this:
> #lang racket
> (require syntax/parse/define (for-syntax racket/syntax))
> (define-simple-macro (define-struct-fields struct:id (field:id ...) v:expr)
> #:with s (generate-temporary #'struct)
> #:with [struct-field ...]
> (for/list ([field (in-list (syntax->list #'(field ...)))])
> (format-id #'struct "~a-~a" #'struct field))
> (begin
> (define s v)
> (define field (struct-field s))
> ...))
> ;; testing it out
> (struct test (a b c))
> (define x (test 1 2 3))
> (define-struct-fields test (a b) x)
> a
> b
>
> Or do you want it even more automatic than that?
>
> On Aug 17, 2015, at 11:29 PM, Deren Dohoda <deren.doh...@gmail.com> wrote:
>
> Suppose I have a struct which implements a generic interface. I'll copy
> and paste the interface from the guide for the example. What I'd like to do
> is have automatically-introduced syntax which allows you to skip a lot of
> the struct-accessor forms. So for instance, for a struct like
> (struct test (a b c))
>
> I'd like, in a method, to be able to say
> (define (some-method genericable)
> (define-accessors (a b)))
> Which is essentially a (define-values ...) expression, taking care of the
> messy work of typing out all the accessor methods like (test-a genericable).
>
> I have this example, which doesn't raise any syntax errors, and looks
> exactly like I'd expect from the macro stepper's output, yet fails when run:
>
> #lang racket/base
> (require (for-syntax racket/base)
> racket/generic)
>
> (define-generics printable
> (gen-print printable [port])
> (gen-port-print port printable)
> (gen-print* printable [port] #:width width #:height [height])
> #:defaults ([string?
> (define/generic super-print gen-print)
> (define (gen-print s [port (current-output-port)])
> (fprintf port "String: ~a" s))
> (define (gen-port-print port s)
> (super-print s port))
> (define (gen-print* s [port (current-output-port)]
> #:width w #:height [h 0])
> (fprintf port "String (~ax~a): ~a" w h s))]))
>
> (define-syntax (pstruct stx)
> (syntax-case stx ()
> ((_ struct-name (accessors ...) [body ...])
> (with-syntax ((sv (datum->syntax stx 'struct-values)))
> #'(struct struct-name (accessors ...)
> #:methods gen:printable
> [(define-syntax (sv stx)
> (syntax-case stx ()
> ((_ (acc (... ...)))
> (let ((accs (for/list ((id (syntax->datum #'(acc (...
> ...)))))
> (string->symbol (format "~a-~a" 'struct-name
> id)))))
> (with-syntax ((s (datum->syntax stx 'ps))
> (as (datum->syntax stx accs)))
> #'(define-values (acc (... ...)) (apply values (map
> (λ(proc) (proc s)) as))))))))
> body ...])))))
>
> (pstruct test (a b c)
> [(define (gen-print ps)
> (struct-values (a))
> a)])
>
> Welcome to DrRacket, version 6.2 [3m].
> Language: racket/base [custom]; memory limit: 1024 MB.
> > (gen-print (test 1 2 3))
> . . gen-print: not implemented for #<test>
>
> How am I going wrong here?
>
> Thanks,
> Deren
>
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