NetNews Offline 2/NetNews Offline Volume 2.iso/news/comp/lang/c-part1/3428

Internet Message Format | 1996-08-05 | 1.7 KB

Path: mail2news.demon.co.uk!genesis.demon.co.uk
From: Lawrence Kirby <[e-mail]>
Newsgroups: comp.lang.c
Subject: Re: newbie--what's wrong with this?
Date: Sun, 28 Jan 96 22:27:34 GMT
Organization: none
Message-ID: <[e-mail]>
References: <4ee8gk$[e-mail]>
Reply-To: [e-mail]
X-NNTP-Posting-Host: genesis.demon.co.uk
X-Newsreader: Demon Internet Simple News v1.27
X-Mail2News-Path: genesis.demon.co.uk

In article <4ee8gk$[e-mail]> [e-mail] "James Hamp" writes:

>Rule->CompRule = (COMPARERULE *)malloc(2 * sizeof(COMPARERULE));
>
>/* Initialize first compare rule, then... */
>
>Rule->CompRule++;
>^^^^^^^^^^^^^^^^^   This didn't work--when I initialized the second rule
>                    (or so I thought), it went into the first rule.

Actually it did work except that it did more than you expected. This
increments Rule->CompRule and therefore makes that point to the second rule.
To access the first rule using the pointer you would then need something
like Rule->CompRule[-1] and to access the 2nd you need Rule->CompRule[0].

>Thinking I had a precedence problem, I tried
>
>(Rule->CompRule)++;
>
>and the same thing happened.

Right - that means the same thing.

>I know I'm being stupid here--my try that worked was
>to initialize the second rule with Rule->CompRule[1].members.  Since I
>made it work, the code's okay, but I'd like to know what I'm not under-
>standing.

Right, that simply accesses/updates the 2nd entry without changing the
pointer. Therefore future uses of that pointer worked as you expected.

--
-----------------------------------------
Lawrence Kirby | [e-mail]
Wilts, England | [e-mail]
-----------------------------------------