Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!rice!uw-beaver!zephyr.ens.tek.com!tekgen!sail!toma
From: toma@sail.LABS.TEK.COM (Tom Almy)
Newsgroups: comp.lang.lisp
Subject: Re: weird common lisp feature
Keywords: read, read-line
Message-ID: <9026@sail.LABS.TEK.COM>
Date: 25 Feb 91 16:37:43 GMT
References: <12413@helios.TAMU.EDU> <1991Feb21.104336.26012@Think.COM> <18935@brahms.udel.edu> <964@creatures.cs.vt.edu>
Reply-To: toma@sail.LABS.TEK.COM (Tom Almy)
Organization: Tektronix, Inc., Beaverton,  OR.
Lines: 30

In article <964@creatures.cs.vt.edu> lavinus@csgrad.cs.vt.edu () writes:
>Everyone seems to be missing a basic point of Lisp philosophy: If you do
>something like (foo a) (foo2 b), you should not count on that being evaluated
>left-to-right or right-to-left.  Generally, it is good programming practice
>(in general, but especially in Lisp) not to make any assumptions about order
>of evaluation unless the *language* (not the compiler) guarantees some
>particular order (the only example I can think of offhand is C - it guarantees
>order of evaluation of most everything).

I believe you are exactly backwards on this, with one small exception.

Quoting from CL:TL (2nd Edition) page 75:
"X3J13 voted in October 1988 to clarify that while the arguments in a function
call are always evaluated in strict left-to-right order, whether the function
to be called is determined before or after argument evaluation is
unspecified."

On the other hand, from "The C Programming Language" (1st edition)
pages 49 and 50:
"C, like most languages, does not specify in what order the operands of an
operator are evaluated."
"Similarly, the order in which function arguments are evaluated is not
specified."



-- 
Tom Almy
toma@sail.labs.tek.com
Standard Disclaimers Apply