Re: Is gentemp or gensym "safe"?

[Rob Browning]

Martin Grabmueller <address@hidden> writes:

> You may want to check out the chapter on syntactic extension in
> Dybvig's Book:
> 
> http://www.scheme.com/tspl2d/syntax.html#g2237

Hmm.  Well, I nearly got syntax-rules working as I wanted, but got
stuck with letrec-syntax.  Can you not use it to create internal
helper-macros?

Given this:

  (define-syntax foo
    (letrec-syntax ((xxx (syntax-rules () ((xxx bar) bar)))
                    (yyy (syntax-rules () ((yyy bar) (xxx bar)))))
      (syntax-rules ()
        ((foo a b)
         (+ (xxx a)
            (yyy b))))))

guile complains during usage like this:

  guile> (foo 1 2)
  ERROR: reference to identifier outside its scope xxx
  ABORT: (misc-error)
  guile> 

-- 
Rob Browning <address@hidden> PGP=E80E0D04F521A094 532B97F5D64E3930