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From: net@opal.cs.tu-berlin.de (Oliver Laumann)
Newsgroups: comp.lang.scheme
Subject: Re: evaluating () should be an error
Message-ID: <2977@kraftbus.cs.tu-berlin.de>
Date: 25 Mar 91 10:05:46 GMT
References: <1991Mar24.064144.4256@daffy.cs.wisc.edu>
Organization: Technical University of Berlin, Germany
Lines: 18

In article <1991Mar24.064144.4256@daffy.cs.wisc.edu> quale@saavik.cs.wisc.edu (Douglas E. Quale) writes:
> IMHO, an attempt to evaluate () should be required by the standard to signal
> an error.  This would clean up a bit of lazy coding by forcing the use of '().

I thought the standard did require () to be quoted.  The P1178/D4 says
(section 4.1.3, page 15):

   "Note:  In many dialects of Lisp, the empty combination, (),
   is a legitimate expression.  In Scheme, combinations must
   have at least one subexpression, so () is not a syntactitcally
   valid expression."


Elk signals an error when you try to evaluate () (unless the -bc
(backwards compatibility) option is given on startup).

--
Oliver Laumann    net@tub.cs.tu-berlin.de  net@tub.UUCP  net@gnu.ai.mit.edu