On Sun, 14 Aug 2005, [ISO-8859-1] Jens Axel Søgaard wrote:

> What should I do if I want to give a piece of (expanded) syntax the
> same source information as, say, the macro call?

There can be a primitive for that.  E.g.,
   annotate : (syntax-object, syntax-object) -> syntax-object
In the hash-table, this would insert a new entry for the pair
representing the second syntax object, copying the annotation of the first.

>> Of course.  Syntax objects are still ordinary pairs.  No change to car/cdr
>> is required.  The hash table with source information is kept separately.
>
> Hmm. How do you represent identifiers?

The same way, once you give them a wrap to give them separate identities.

> I believe with-syntax behaves that way in order to be (more) compatible
> with the psyntax-implementation. Note that the source location
> information for stx-expr in
>
>  (with-syntax ((pattern stx-expr) ...) expr)
>
> is taken from stx-expr, when stx-expr is not returning a list. That
> is the source location is still tracked.

Do you know what location is assigned when stx-expr is a list?

As an aside, it is sometimes easy to throw away too much information when using
the destructuring idiom.  For example, in

   (define-syntax let1
     (lambda (form)
       (syntax-case form ()
         ((_ ((i e) ...) e1 e2 ...)
          (syntax (let ((i e) ...) e1 e2 ...))))))

it is unlikely that most implementations would keep the
location of the input subnode ((i e) ...) in the result.

Cheers
Andre