Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!purdue!bu-cs!buengc!bph
From: bph@buengc.BU.EDU (Blair P. Houghton)
Newsgroups: comp.lang.c
Subject: Re: When is a cast not a cast?
Message-ID: <2759@buengc.BU.EDU>
Date: 3 May 89 17:13:41 GMT
References: <2747@buengc.BU.EDU> <10191@smoke.BRL.MIL>
Reply-To: bph@buengc.bu.edu (Blair P. Houghton)
Followup-To: comp.lang.c
Organization: Boston Univ. Col. of Eng.
Lines: 25

In article <10191@smoke.BRL.MIL> gwyn@brl.arpa (Doug Gwyn) writes:
>In article <2747@buengc.BU.EDU> bph@buengc.bu.edu (Blair P. Houghton) writes:
>>10 	p = (c + (char *) i);  /* More trouble than it's worth... */
>
>Addition of pointers is a meaningless operation.

Philosophically, it's rubbish.  According to the language def., it's pure
science.

Apparently, in C, one can not only add apples to oranges and get more
oranges, one can add nothing but apples to the oranges, not even oranges
themselves.

Now, I don't mind being told by the compiler that I'm screwing up by
subtracting pointers that may point to different data spaces (even though
it is my belief that such a subtraction should occur vectorially, and
generate the proper memory offset to get me from ram-byte A to ram-byte B,
going through data/text/etc pages as necessary...) but I find it more than
unsettling that a pointer offset can not be expressed and manipulated
directly in the pointer type.  At least, not without first multiplying or
dividing by the proper sizeof(*type).

				--Blair
				  "A little older,
				   marginally wiser..."