Path: utzoo!attcan!uunet!lll-winken!lll-lcc!ames!mailrus!iuvax!rutgers!njin!princeton!phoenix!rjchen
From: rjchen@phoenix.Princeton.EDU (Raymond Juimong Chen)
Newsgroups: comp.sys.ibm.pc
Subject: Re: correct code for pointer subtraction (correction to typos)
Message-ID: <5138@phoenix.Princeton.EDU>
Date: 4 Jan 89 22:52:24 GMT
References: <5137@phoenix.Princeton.EDU>
Organization: Princeton University, NJ
Lines: 31

I know it's bad form to follow up to one's own article, but
the number of typos I found after posting it was embarrassing.

> explicitly states "p-q is the numebr of elements between p and q".
                                number

> The additional code is really very simply.  If the carry is clear, then
                                     simple

>               the accumulator contains the two-s complement of the 
> absolulte value of the byte difference.

More clearly (and spelled correctly), the accumulator contains the two's
complement of the absolute value of the number of bytes separating the
two pointers.

> But I suspect most people would argue that the original code
> (which used the line printf("%ld\n", &a[30000] - a); ) is ANSI-conformant,
                              "%d\n"                   ((oops))

> Let M be 2^sizeof(int), so that an unsigned can represent the values
> 0 ... M-1,  ...

Of course, that should be ``Let M be 2^(number of bits in an int)''.

Apologetically,
-- 
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