From: "Marp" <marp AT 0 DOT 0 DOT 0 DOT 0>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Type casting and pointers
Date: Wed, 1 Aug 2001 17:59:40 -0400
Organization: MindSpring Enterprises
Lines: 58
Message-ID: <9k9u34$d9c$1@slb7.atl.mindspring.net>
References: <wyZ97.2407$n_3 DOT 3163465 AT typhoon DOT ne DOT mediaone DOT net>
NNTP-Posting-Host: 9e.fc.1f.18
X-Server-Date: 1 Aug 2001 21:59:00 GMT
X-Priority: 3
X-MSMail-Priority: Normal
X-Newsreader: Microsoft Outlook Express 5.50.4522.1200
X-MimeOLE: Produced By Microsoft MimeOLE V5.50.4522.1200
To: djgpp AT delorie DOT com
DJ-Gateway: from newsgroup comp.os.msdos.djgpp
Reply-To: djgpp AT delorie DOT com

The only purpose of typecasting in the example given is to suppress a
compiler warning. It's not a good example :-) Normally you would use
typecasting to override the compiler's default behavior in promoting data
types.

Given this:

int a = 1;
double b = 2.5;
double c;

And this:

c = a + b;

The variable c will hold 3.5 because the compiler promotes a to double for
the purposes of the addition.

But this:

c = a + (int)b;

The variable c will hold 3 since you told it to demote b to int (which
causes it to use the truncated value of b for addition).

BTW, you get a warning in the book's example without a cast because you are
assigning a float ** to a float *. They are not the same thing.

Hope this helps.

- Marp

"Steve Dondley" <stevedondley AT mediaone DOT net> wrote in message
news:wyZ97.2407$n_3 DOT 3163465 AT typhoon DOT ne DOT mediaone DOT net...
> Hello,
>
> I've got a newbie C question.  I've got a beginner's C book that doesn't
> explain something very well. Example code from the book:
>
> float *p;
> float balance[10][5];
> ...assignment stuff here...
> p = (float *) balance;
>
> My code works just fine without the (float *) type cast, but I do get a
> warning.  Why exactly do you need it?  Doesn't declaring *p as a float
> pointer at the top of the source take care of that?  The book also never
> explains what exactly the asterisk in (float *) is.  I'm just assuming it
> type casts the pointer.
>
> Can someone please provide some elucidation?  Thanks!
>
> ---Steve
>
>
>