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000014_icon-group-sender_Wed Feb 12 08:13:21 2003.msg
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Received: (from root@localhost)
by baskerville.CS.Arizona.EDU (8.11.1/8.11.1) id h1CFDKf14816
for icon-group-addresses; Wed, 12 Feb 2003 08:13:20 -0700 (MST)
Message-Id: <200302121513.h1CFDKf14816@baskerville.CS.Arizona.EDU>
X-Sender: whm@mail.mse.com (Unverified)
Date: Wed, 12 Feb 2003 01:00:58 -0700
To: ernobe <ernobe@yahoo.com>
From: "William H. Mitchell" <whm@mse.com>
Subject: Re: data values (and bounded expressions)
Cc: icon-group@cs.arizona.edu
Errors-To: icon-group-errors@cs.arizona.edu
Status: RO
There's a good discussion of bounded expressions on 90-92 in "The Icon
Programming Language", on the website. The key point is that if an
expression is bounded and it produces a result, all/any suspended
generators in the expression are discarded.
You can find a somewhat different explanation of the topic in some slides
for an Icon class I'm currently teaching. Here's the URL for that growing
set of slides: http://www.cs.arizona.edu/classes/cs451/icon.pdf. See slide
72 and following. NOTE that the PDF was generated with WordPerfect and
some browser plug-ins blow up on it. If so, download it and then view it
as a file.
At 03:34 PM 2/11/03 -0600, ernobe wrote:
>
>[In the implementation book,] in Chapter 2, page 17, there appears that,
>"Except in such specific situations, expressions are not bounded". The
>specific situations mentioned are the if-clause and the control clauses
>of loops. The confusion here is that the if expressions and loops are
>also themselves expressions, and when they do not appear as arguments to
>other expressions they are bounded. The previous mention of unbounded
>expressions referred to them as arguments to be evaluated (p.16) which
>was seen to resemble a logical conjunction (p.15). All of which leads
>us to the conclusion that a clearer statement than the one cited would
>be "Except in such specific situations, logical expressions are not
>bounded."