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Date: Fri, 21 Jul 2006 10:23:04 -0700
From: glen herrmannsfeldt <gah@ugcs.caltech.edu>
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Subject: Re: ONES COMPLEMENT
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Date: 2006-07-21T10:23:04-07:00
List-Id: <comp.lang.ada>

Shmuel (Seymour J.) Metz wrote:

(snip)

> Robin wrote "A properly designed 1s complement machine would not
> generate -0 in normal arithmetic operations."

> I responded "0+(-0)?".

> You responded "A subtractive adder."

> I'm trying to say that there's nothing about 0+(-0) requiring a
> subtractive adder.

There are adder designs that reduce the generation of -0.

In any case, Seymour Cray, who probably knows more about fast
processor design than anyone reading this newsgroup, designed
ones complement machines for many years.  There is also a lot
of literature on processor design.

Fortran and C definitely allow ones complement arithmetic, so a standard 
conforming program for those languages has to allow for it.

(I didn't look it up for PL/I or ADA, but most likely they do, too.
Java is the only language that I know doesn't allow it.)

Unless someone wants to go to the literature and find the known
answers, there doesn't seem to be much point in arguing it here.

-- glen