Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!cs.utexas.edu!uunet!mcvax!ukc!etive!aiai!jeff
From: jeff@aiai.ed.ac.uk (Jeff Dalton)
Newsgroups: comp.lang.lisp
Subject: Re: Simple question RE nested DEFUNs
Message-ID: <665@skye.ed.ac.uk>
Date: 2 Aug 89 11:13:38 GMT
References: <89Jul31.114325edt.11243@ephemeral.ai.toronto.edu> <979@accuvax.nwu.edu> <86124@ti-csl.csc.ti.com>
Reply-To: jeff@aiai.UUCP (Jeff Dalton)
Organization: AIAI, University of Edinburgh, Scotland
Lines: 34

In article <86124@ti-csl.csc.ti.com> gateley@m2.UUCP (John Gateley) writes:
>In article <979@accuvax.nwu.edu> Krulwich@eecs.nwu.edu (Bruce Krulwich) writes:
>>...  Additionally, the semantics of
>>DEFUN are clear: it always defines a global function.
>
>Not true: defun is a top level form; its semantics are defined only
>in the case where it appears at top level (see CLtL chap 5). In the
>case mentioned in the original article, the defun does not appear
>at top level.

Page 66 supports your view.  Page 67, however, says:

   Evaluating a {\tt defun} form causes the symbol {\it name} to be
   a global name for the function specified by the lambda-expression

      (lambda ...)

   defined in the lexical environment in which the {\tt defun} form
   was executed.  Because {\tt defun} forms normally apear at top
   level, this is normally the null lexical environment.

It's possible to argue for a long time about whether page 66 or
page 67 should win.  X3J13 may have decided this one way or the
other by now.  But most implementations do allow {\tt defun} in
non-top-level contexts.

Note too that it's possible to come up with examples in which
a non-top-level {\tt defun} is silly.  But that doesn't show
that every case is silly.  And, indeed, there are times when
non-top-level {\tt defun} makes sense.

Jeff Dalton,                      JANET: J.Dalton@uk.ac.ed             
AI Applications Institute,        ARPA:  J.Dalton%uk.ac.ed@nsfnet-relay.ac.uk
Edinburgh University.             UUCP:  ...!ukc!ed.ac.uk!J.Dalton