On Tue, Jul 16, 2002 at 07:42:25AM -0700, Sean O'Rourke wrote:
> On Tue, 16 Jul 2002, Nicholas Clark wrote:
>
> > 5.8.0 does the full fun and games of integer or floating point comparison:
> >
> > perl5.8.0-64 -le '$a = ~0; $b = $a & ~1; printf "%x <=> %x\n", $a, $b; print $a
><=> $b; {use integer; print $a <=> $b}'
> > ffffffffffffffff <=> fffffffffffffffe
> > 1
> > 1
> >
> > IIRC the speed difference was hard to benchmark. However, the ability to
> > deal with large file offsets, windows device numbers and other 64 bit
> > quantities correctly was seen as useful.
>
> Let's not lose sight of the forest for the trees here -- the comparisons
> are now *backwards*, which is considerably worse than imprecise. Here's
I had. I didn't realise that this was the current situation.
> what I think the multimethod dispatch version would look like, without the
> automatic multimethod dispatch:
>
> INTVAL cmp (PMC* value) {
> if (value->vtable == &Parrot_base_vtables[enum_class_PerlString]) {
> FLOATVAL fdiff = (FLOATVAL)self->cache.int_val
> - value->vtable->get_number(INTERP, value);
> if (fdiff == 0) {
> INTVAL idiff = SELF->cache.int_val
> - value->vtable->get_integer(INTERP, value);
> return idiff > 0 ? 1 : diff < 0 ? -1 : 0;
> } else {
> return fdiff > 0 ? 1 : -1;
> }
When we get back to worrying about the details, I think NaNs are going to
return -1. I'm not sure if this is a huge concern yet, although it could
get confusing if A cmp B is -1, and so is B cmp A.
> }
> else if (value->vtable == &Parrot_base_vtables[enum_class_PerlNum]) {
> FLOATVAL diff;
> diff = (FLOATVAL)SELF->cache.int_val
> - value->vtable->get_number(INTERP, value);
> return diff > 0 ? 1 : diff < 0 ? -1 : 0;
> }
> else {
> /* int or indef */
> INTVAL diff = SELF->cache.int_val
> - value->vtable->get_integer(INTERP, value);
> return diff > 0 ? 1 : diff < 0 ? -1 : 0;
> }
> }
>
> Why not drop something like this in for the moment, then take another look
> when we have multimethods?
Putting in something that works well enough, and flagging it for a revisit
later seems like a very good solution.
Nicholas Clark
--
Even better than the real thing: http://nms-cgi.sourceforge.net/
