Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!swrinde!elroy.jpl.nasa.gov!decwrl!csus.edu!ucdavis!csusac!usenet
From: cs16011@athena.ecs.csus.edu
Newsgroups: comp.lang.lisp.franz
Subject: Re: Lisp Macros
Message-ID: <1991May17.053812.18600@csusac.csus.edu>
Date: 17 May 91 05:38:12 GMT
References: <1991May15.203735.3850@csusac.csus.edu>
Sender: usenet@csusac.csus.edu (News account (alt))
Organization: California State University, Sacramento
Lines: 18


Thanks for all the information!  Let me clarify my question a little bit.
My instructor asks "whether macros can be recursive in Lisp and if so or
not so, support one's answer".  When I tried to tackle that question I
thought that since macro expansion was a two-step process in which the
first phase will build a template of "to-be-evaulated" code while the
second phase will evaluate the code built, and also because the Lisp
interpreter will try to expand the first element of the built code
further if it is a macro name (or if it is just a regular Lisp primitive
then the code will be evaulated and the result returned), then it seems
logical that I can have recursive macros merely by controlling how the
"to-be-evaluated" code is composed during phase one.  On the other hand,
my instructor thinks that recursive macros will have the problem of
unable to exit but keep on expanding forever.  Other than this idea,
he has not provided any concrete evidence that it cannot be done.
I have not contrived any recursive macros before and think it be more
appropriate to learn from worldwide Lisp experts here.  Can macros have
double recursion or just single tail recursion or NO recursion at all?