[Python-Dev] Negated hex/oct constants (SF #660455)

[Guido van Rossum]

> >   >>> -(0xffffffff)
> >   1
> >   >>> -0xffffffff 
> >   -4294967295L                          <<<<-------- !!!
> >   >>> 
> 
> This is my main concern - that there is an inconsistency between
> -(0xffffffff) and -0xffffffff.

Mine too. :-)

> I think whatever is decided, this inconsistency should be fixed for
> 2.3 (and possibly back-ported to 2.2).
> 
> So we end up with either
> 
>     0xffffffff == -1
>     -0xffffffff == 1
> 
> or
> 
>     0xffffffff == 4294967295L
>     -0xffffffff == -4294967295L
> 
> and 0xffffffff is going to stay as -1 until 2.4 ...

We can't do the latter; 0xffffffff was always -1, and changing it
without at least giving a warning for one release is too abrupt.

The problem with fixing it in 2.3 so that -0xffffffff is 1, is that it
keeps changing between releases: up through 2.1 it was 1, in 2.2 it
was -4294967295L, in 2.3 it would be 1 again, and in 2.4 it would be
-4294967295L again!!!

The only saving grace is that few people ever use such hex constants
with a minus sign in front of them.  But even then, I'm not sure of
the back-and-forth is worth it.  And while you can say, "so fix it in
2.2.3 too", that doesn't mean that everybody will upgrade.

--Guido van Rossum (home page: http://www.python.org/~guido/)