Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!uunet!snorkelwacker!bloom-beacon!ZURICH.AI.MIT.EDU!jinx
From: jinx@ZURICH.AI.MIT.EDU ("Guillermo J. Rozas")
Newsgroups: comp.lang.scheme
Subject: - and / with one argument should be identity functions.
Message-ID: <8911151802.AA29786@zurich.ai.mit.edu>
Date: 15 Nov 89 18:02:36 GMT
References: <4520@skiscs.vu.nl>
Sender: daemon@bloom-beacon.MIT.EDU
Reply-To: jinx@zurich.ai.mit.edu
Organization: The Internet
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   Date: 13 Nov 89 17:17:21 GMT
   From: Via Fons Botman <mcsun!hp4nl!star.cs.vu.nl!xerox@uunet.uu.net>

   PLease, let's *not* define (- X) and (/ X) to be something else
   than X. It might be the source of obscure errors in (admittedly
   ugly) code like:

   (define (net-gain gain losses) (apply - gain losses))

You should be using some version of reduce here.  Apply is generally
the wrong thing to use.

   Besides that, it may be cute, but it is neither clear nor
   consistent, and therefore not "in the spirit of Scheme".

Why isn't it consistent?  - and / are left associative and thus it is
natural and consistent to place the (right) identity on the left. :-)

Although (/ x) is atypical, that can hardly be said for -.  Most
languages treat unary - specially.  In addition, the "special" meaning
for both is traditional in Lisp.