| glen herrmannsfeldt 2006-07-21, 7:01 pm |
| 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
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