Re: define - any name

[Ken Anderson]

Olin Shivers taught me the trick that in Scheme, you can write macros in a way 
that will allow "," to be used to unquote arguments in the macro.

If nothing else you could define a macro, (define-type name fields) that would 
work something like this:

(define-type
  fride-vote-msg-type
  `((id:         ,fride-id-msg-type)
    (referendum: ,fride-id-reference-msg-type)
    (date:       int)
    (vote:       int)))

But with Olin's style it could look something like:
(define-type
  fride-vote-msg-type
  (id:         ,fride-id-msg-type)
  (referendum: ,fride-id-reference-msg-type)
  (date:       int)
  (vote:       int))

At 09:22 AM 4/19/2003 +0200, Egil Moeller wrote:
>At the moment, I have a function (list-entry type name), that given a
>"type-definition" (a binary tree with names in), and a name, constructs a
>function that will extract the entity at the position corresponding to
>that name in the type, in a binary tree given as argument. The
>"type-definition" i often constructed from other such definitions:
>
>(define fride-vote-msg-type
>  `(list
>    (id:         ,fride-id-msg-type)
>    (referendum: ,fride-id-reference-msg-type)
>    (date:       int)
>    (vote:       int)))
>
>I use the list-entry function, then to construct a set of
>"access-functions", e.g.
>
>(define fride-vote-list.id (fride-list-entry fride-vote-msg-type 'id))
>(define fride-vote-list.referendum (fride-list-entry fride-vote-msg-type 
>'referendum))
>
>This is both quite some extra work, and also makes the code clumsier, than
>if those functions could be automatically created. I'd like to write
>something like
>
>(define-type fride-vote-msg-type
>  `(list
>    (id:         ,fride-id-msg-type)
>    (referendum: ,fride-id-reference-msg-type)
>    (date:       int)
>    (vote:       int)))
>
>and have them all created. For this purpose I have created a function that
>finds all names in a type-definition that can be used to create such
>access-functions.
>
>The question i, how do I go on from here? I'd like to make a macro, but
>that would not let the backqoute be evaluated in the correct
>environment... What I would need is a (define-unquoted-in-toplevel name
>value), that would work like an ordinary funcion, evaluating its
>arguments, and bind the value of name to the value of value, in the
>top-level surrounding environment... Is this really not something people
>have wanted before?
>
>My idea about environments in quile is that they, due to speed
>considerations or something, are a bit too limited... For example, an
>eval-closure is _not_ an ordinary environment/can't be treated like one,
>and one can not do (eval) with such an object as environment...
>
>Regards,
>Egil
>
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