Newsgroups: comp.arch
Path: utzoo!henry
From: henry@utzoo.uucp (Henry Spencer)
Subject: Re: negative addresses (really unsigned arithmetic)
Message-ID: <1988May15.220044.12987@utzoo.uucp>
Organization: U of Toronto Zoology
References: <2393@uvacs.CS.VIRGINIA.EDU> <9485@apple.Apple.Com>, <11571@ut-sally.UUCP>
Date: Sun, 15 May 88 22:00:44 GMT

> Your CS background is showing, gentlemen.  When I gather data from stars, I
> count the precious photons one at a time, and use unsigned arithmetic to
> massage them, since there are no negative photons...

Your lack of CS background is showing, Ed. :-)  Just because your numbers
are always positive doesn't mean you should use unsigned data types for
them.  As people have already pointed out, nasty surprises lurk in unsigned
arithmetic, and it is potentially less efficient to boot (although on most
machines the difference, if any, is slight).  The only compelling reason
to use unsigned data types for ordinary arithmetic purposes is if you really
need that one extra bit... and if that's the case, you're probably better
off using some sort of multi-precision arithmetic package anyway, because
sooner or later you'll need another bit.
-- 
NASA is to spaceflight as            |  Henry Spencer @ U of Toronto Zoology
the Post Office is to mail.          | {ihnp4,decvax,uunet!mnetor}!utzoo!henry