<HTML>In a message dated 5/23/2003 10:13:07 PM Central Daylight Time, mcj4@ukc.ac.uk writes: <BLOCKQUOTE TYPE=CITE style="BORDER-LEFT: #0000ff 2px solid; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px; PADDING-LEFT: 5px">I get a complaint about #%app not being bound, in particular with respect to my calls to 'vector-ref'. I've read the docs on this a few times; I don't think it's unclear, but I do think I don't understand.</BLOCKQUOTE> This error message should be really read as "macro messed with the hygiene; the module system detects that the author got the hygiene marks wrong" ;) I actually get a different error message when I use your code and example: > (let ((v (vector 1 2 3)) >         (v2 (vector 4 5)) >         (v3 (vector 6))) >     (bind ((v a b c) (v2 d e) (v3 f)) >           (list v.a v.b v.c v2.d v2.e v3.f))) gives me an error that v is not bound, which is really the same problem (that is, the syntax "marks" on v in the macro result are somehow not the same as those for the v bound in my own let binding). I think part of the problem is that you throw away all syntax info very early on, with the call to syntax-object->datum. Then, in building up the let bindings, it is unclear actually what syntax information will be associated with both the vector binding names (v, v2, and v3) and vector-ref. To be safer only the v.a, v.b, etc. should be "washed" through datum->syntax-object. The following code works, producing "(1 2 3 4 5 6)" for the above example. Note that I produce the list of let bindings as a list of syntax, rather than lists. #cs (module bind mzscheme     (provide bind)     (define-syntax (bind e)     (define (process-binding vnm flst)       (let loop ((pos 0)                  (flst flst))         (if (null? flst)             '()             (cons              #`(#,(datum->syntax-object                    e                    (string->symbol                     (string-append (symbol->string (syntax-object->datum vnm))                                    "."                                    (symbol->string (syntax-object->datum (car flst))))))                  (vector-ref #,vnm #,pos))              (loop (+ pos 1) (cdr flst))))))     (define (make-bindings v-names flst-lists)       (apply append              (map process-binding v-names flst-lists)))     (syntax-case e ()       ((_ ((v* f ...) ...) code ...)        #`(let #,(make-bindings (syntax->list #'(v* ...))                                (map syntax->list (syntax->list #'((f ...) ...))))            code ...))))) Jim </HTML>