Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!uwm.edu!bionet!agate!ucbvax!CS.ARIZONA.EDU!cjeffery
From: cjeffery@CS.ARIZONA.EDU (Clinton Jeffery)
Newsgroups: comp.lang.icon
Subject: Multiple value assignment in icon???
Message-ID: <9103190605.AA25040@cheltenham.cs.arizona.edu>
Date: 19 Mar 91 06:05:09 GMT
References: <1991Mar18.150838.24597@midway.uchicago.edu>
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>>Also, I hesitated somewhat at creating a co-expression just to do
>>something that short that I'm likely to use quite a lot. Isn't that
>>likely to be quite expensive in terms of garbage produced? Or would
>>reusing the same temporary to hold it mean that reference counting or
>>something rescues things?

>You know, I really don't know.  Co-expressions involve less overhead
>than a procedure call, as I understand them, and are a bit faster.

Basically everyone is right.
Co-expression >activation< involves less overhead and is a bit faster
than procedure call.  Co-expression >creation< does involve some work
setting up stacks and copying variables.  In many of these situations
there is some magic "average number of results" beyond which co-expressions
are cost-effective.  But of course, Icon is focused on programmer
time more than on execution time.  If you are a busy person and you
are in the habit of avoiding co-expressions for performance reasons,
not only will you miss out on a lot of fun, you will spend a lot more
time writing and debugging, and often you will not gain enough to
have justified it.

Clint

P.S. I have been guilty of avoiding co-expressions before!  Its very
understandable and really is justified, AFTER the program is finished
and you are tuning it.  Why not write it in two lines with a co-expression
first, and write yourself a comment to look at it again later...