Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!ig!arizona!mike
From: mike@arizona.edu (Mike Coffin)
Newsgroups: comp.lang.lisp
Subject: Re: Overloading of NIL (as empty list and logical falsity)
Message-ID: <9840@megaron.arizona.edu>
Date: 22 Mar 89 19:47:14 GMT
References: <8247@csli.STANFORD.EDU>
Distribution: na
Organization: U of Arizona CS Dept, Tucson
Lines: 16

From article <8247@csli.STANFORD.EDU> (Mark Johnson):
[Speaking of the overloading of nil and the empty list in Lisp]
> Does anybody else have any comments on the matter?  Do more advanced
> functional languages (ML?) incorporated the same overloading of NIL?

Scheme has distinct values for false and the empty list: #F and '(),
respectively.  Any Scheme value can be used as a boolean value for the
purpose of a conditional test. Any value except #F and the empty list
count as "true";  #F and the empty list count as "false".  This seems
to be the best of both worlds to me...

-mike
-- 
Mike Coffin				mike@arizona.edu
Univ. of Ariz. Dept. of Comp. Sci.	{allegra,cmcl2}!arizona!mike
Tucson, AZ  85721			(602)621-2858