[gambit-list] destructuring bind define-type

lowly coder lowlycoder at huoyanjinjing.com
Tue Jun 2 01:22:01 EDT 2009


Suppose I have the following:

(define-type p3 x y z)

(define (with-cons c func) (func (car c) (cdr c))))

(define (with-p3 p func) (func (p3-x p) (p3-y p) (p3-z p)))

(define p (cons (make-p3 1 2 3) (make-p3 4 5 6)))

Now, ideally I want to write:

(destructure-bind (cons (p3 x1 y1 z1) (p3 x2 y2 z2))
  (make-point3 (+ x1 x2) (+ y1 y2) (+ z1 z2)))

How can I do this with with-cons / with-p3? (It seems I can only go done one
level of nesting).

Thanks!



On Mon, Jun 1, 2009 at 9:45 PM, David Rush <kumoyuki at gmail.com> wrote:

> 2009/6/2 lowly coder <lowlycoder at huoyanjinjing.com>:
> > are there any amcros that play well with destructuring bind of
> define-type's
> > ? I just want to check to see if there's a pre-existing solution before
> > re-inventing my own.
> >
> > I find myself writing way too much code of the form:
> >
> > (define-type foo a b)
> > (define-type bar c d)
> >
> > (lambda (x)
> >   (let ((c (bar-c x) (d (bar-d x)))
> >     (let ((a (foo-a a) (b (foo-b b)) ...
>
> This is the kind of thing where macros get over-used
>
> (define (with-foo f body) (body (foo-a f) (foo-b f)))
>
> david
> --
> GPG Public key at http://cyber-rush.org/drr/gpg-public-key.txt
>
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