ftp.cs.arizona.edu/ftp.cs.arizona.edu.tar/ftp.cs.arizona.edu/icon/newsgrp/group94b.txt/000062_icon-group-sender _Tue Sep 20 15:30:41 1994.msg

Internet Message Format | 1995-02-09 | 2KB

Received: by cheltenham.cs.arizona.edu; Tue, 20 Sep 1994 15:46:32 MST
From: Nevin Liber <nevin@caslon>
Message-Id: <[e-mail]>
Subject: Re: Question: conjunction in Icon and C
To: [e-mail] (Art Eschenlauer)
Date: Tue, 20 Sep 1994 15:30:41 -0700 (MST)
Cc: [e-mail]
In-Reply-To: <[e-mail]> from "Art Eschenlauer" at Sep 20, 94 03:41:27 pm
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Art Eschenlauer proudly drove the following message along the Information SuperHypeway(TM) at breakneck speeds:

> In Icon, if I say:
> if <expr1> & <expr2> then <expr3> else <expr4>
> and <expr1> fails, <expr2> will not be evaluated.
>
> In C, if I say:
> if ( <expr1> && <expr2> ) <expr3>; else <expr4>;
> and <expr1> has a value of zero (NULL, etc.), is it defined (in the ANSI
> standard, I guess) whether <expr2> will be evaluated or is this compiler
> specific?

In C, if <expr1> has a value of 0, then <expr2> is not evaluated, and
the value of the expression ( <expr1> && <expr2> ) is 0.  If <expr1>
has a non-zero (true) value, then <expr2> is evaluated, and the value
of the expression ( <expr1> && <expr2> ) is 0 if <expr2> is 0,
otherwise, the value is 1 (unlike Icon, where you might expect it to be
the same as <expr2>).  This is specified in both K&R 1 as well as the
ANSI C standard.
--
    Nevin ":-)" Liber    [e-mail]    [phone]
                                                  ^^^ (520) after 3/95