On Fri, May 17, 2002 at 03:27:44PM -0400, Dan Sugalski wrote: > At 8:04 PM +0100 5/17/02, Nicholas Clark wrote: > >On Thu, May 16, 2002 at 08:37:32PM -0400, Dan Sugalski wrote: > >> Pssst. Brent. Don't tell anyone, but ~0 *is* -1... :) > > > >$ perl -le 'print ~0' > >4294967295 > >$ perl -le 'print -1' > >-1 > > > >What language were we talking about? :-) > > C, of course. Perl's floating point and integer semantics are another
Do any platforms exist where integers are stored either in 1s complement, or as sign and magnitude? [Your C is a subset of ANSI C :-) Admittedly the useful subset] > matter entirely. Pity that Doing The Right Thing is such a pain. :( Well, it was more doing the right thing with backwards compatibility. *If* perl programmers wrote ~0 when they meant (unsigned int)-1 [or perl6 forced this discipline onto them] then it would be possible to have -4.99, -5.0 and -5.01 convert to 0 in unsigned context, which some people see as more reasonable. The upshot of keeping things locally sane is that -Inf converts to 0x80000000 in unsigned context. (on a system with 32 bit integers) (Yes, perl5 does assume a 2s complement in the C code, but I have a patch locally that I believe eliminates all places where that assumption is made) The trouble is, that everyone is used to DWIM, and $foo & -1 meaning $foo & ~0, so it would probably not be a good thing to change. Nicholas Clark -- Even better than the real thing: http://nms-cgi.sourceforge.net/
