Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ncar!ico!ism780c!haddock!suitti
From: suitti@haddock.ima.isc.com (Stephen Uitti)
Newsgroups: comp.lang.c
Subject: Re: When is a cast not a cast?
Message-ID: <12934@haddock.ima.isc.com>
Date: 2 May 89 23:38:51 GMT
References: <2747@buengc.BU.EDU>
Reply-To: suitti@haddock.ima.isc.com (Stephen Uitti)
Organization: Interactive Systems, Boston
Lines: 27

In article <2747@buengc.BU.EDU> bph@buengc.bu.edu (Blair P. Houghton) writes:
>I wanted to make all the types match up, so I was using casts
>wherever a promotion might be non-obvious.  In particular, I fell for:
>3	char *c;
>5	int i;
>7	c = "somestring";  /* Nothing fancy, null-terminated. */
>8	i = 4;  /* For example. */
>10 	p = (c + (char *) i);  /* More trouble than it's worth... */
>wherupon cc(1) said that the 'operands of + have incompatible types'
>
>Now, who is having the more serious problem with (reduntantly?) casting
>i to be a char * before this addition: me, or the programmming tools
>under Ultrix version 2.2?

It isn't even redundant.  It means the wrong thing.  Casts tend not
to be redundant.  Sometimes they are used for "portability".  Not here.

A better example is
	p = "foobar" + "barfoo";	/* what does this mean? */
The line
	p = c + i;	/* means p = c[i] or p = i[c] or p = i + c */
does something useful.

K&R says something about what arithmetic can be done with pointers.
I'd quote from the bible were it required.

Stephen.