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From: hohendor@lan.informatik.tu-muenchen.dbp.de (Christian Hohendorf)
Newsgroups: comp.lang.scheme
Subject: extend-syntax
Message-ID: <4215@tuminfo1.lan.informatik.tu-muenchen.dbp.de>
Date: 30 Aug 90 23:04:56 GMT
Sender: news@lan.informatik.tu-muenchen.dbp.de
Distribution: comp
Organization: Inst. fuer Informatik, Technische Univ. Muenchen, West Germany
Lines: 31

Hello experts,

I have ported "extend-syntax", a kind of easy-to-understand macro replacement,
the MacScheme code of which came across the net some years ago, to some other
scheme implementations. Now I'm having trouble replacing macros by extend-
syntax (for compatibility's sake). In my opinion, the following should work:

(let ((var '()))
  (extend-syntax (test)
                 ((test) var)
                 ((test q) (set! var (cons 1 var)))
                 ((test q w) (set! var (cons 2 var)))
                 ((test q w e) (set! var (cons 3 var))))))

Calling the macth parameters, extend-syntax claims var not to be bound
  (except when it is also defined globally).

- When calling test without parameters, and var defined globally, extend-syntax
  tries to evaluate the list bound to var. When replacing the corresponding
  line with ((test) 'var), just the symbol var is returned. But I want the non-
  evaluated list bound to that symbol.

Unfortunately, I don't have access to Ken Dybvig's book about Scheme, and I'm
running out of time a bit. Any hints would be heavily appreciated.

Thanks in advance,
     Chris


--
Christian Hohendorf                  hohendor@lan.informatik.tu-muenchen.dbp.de