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From: hoover@cs.UAlberta.CA (Jim Hoover)
Newsgroups: comp.lang.perl
Subject: Re: Yet another perl portability bug
Message-ID: <1990Dec12.042542.28733@cs.UAlberta.CA>
Date: 12 Dec 90 04:25:42 GMT
References: <1990Dec11.052604.21319@cs.UAlberta.CA> <1990Dec11.220809.20201@melba.bby.oz.au>
Sender: news@cs.UAlberta.CA (News Administrator)
Organization: University of Alberta, Edmonton, Canada
Lines: 52

In article <1990Dec11.220809.20201@melba.bby.oz.au> gnb@bby.oz.au 
	(Gregory N. Bond) writes:
>>>>>> On 11 Dec 90 05:26:04 GMT, hoover@cs.UAlberta.CA (Jim Hoover) said:
>
>Jim> 746c747,748
>Jim> < 	return retval;
>Jim> ---
>Jim> 	    /* FIX - memcmp is not guaranteed to return -1 0 +1, just sign */
>Jim> 	    return (retval > 0) ? +1 : -1;
>
>Bzzt.  What it retval == 0?  You mean 
>	return (retval > 0) ? 1 : (retval < 0) ? -1 : 0;
> ...

Sorry, I seem to have become affected by the current trend toward 
obscurity disguised as cleverness.  I could have at least practiced 
what I preach and given more context :)

Within the context of the fix, retval cannot be 0, so the single 
test suffices.  Here is the full context:

    if (str1->str_cur < str2->str_cur) {
	if (retval = memcmp(str1->str_ptr, str2->str_ptr, str1->str_cur))
	    /* HJH - memcmp is not guaranteed to return -1 0 +1, just sign */
	    return (retval > 0) ? +1 : -1;
	else
	    return -1;
    }
    else if (retval = memcmp(str1->str_ptr, str2->str_ptr, str2->str_cur))
	    /* HJH - memcmp is not guaranteed to return -1 0 +1, just sign */
	    return (retval > 0) ? +1 : -1;
    else if (str1->str_cur == str2->str_cur)
	return 0;
    else
	return 1;

(The context, by the way, reflects a two's complement bias that is ubiquitous
in C code.  How much stuff breaks if you switch to a signed-magnitude machine
with +- 0?)


>--
>Gregory Bond, Burdett Buckeridge & Young Ltd, Melbourne, Australia
>Internet: gnb@melba.bby.oz.au    non-MX: gnb%melba.bby.oz@uunet.uu.net
>Uucp: {uunet,pyramid,ubc-cs,ukc,mcvax,prlb2,nttlab...}!munnari!melba.bby.oz!gnb


--
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