Numerification of Order:: constants

[Mark Reed]

S03, lines 418-420: "[cmp] always returns C<Order::Increase>,
C<Order::Same>, or C<Order::Decrease> (which numerify to -1, 0, or +1)."

Shouldn't Order::Increase numerify to +1 and Order::Decrease to -1? In
which case it would be clearer to put them in respective order above...

[Mark A Biggar]

"$a cmp $b" has always been define as sign($a - $b), so the above numerification are correct. Thnk of them as describing the sequence ($a, $b). if the sequence is increasing then "$a, cmp $b" returns Order::Increase or -1.

Mark Biggar

--
Mark Biggar
ma...@biggar.org
mark.a...@comcast.net
mbi...@paypal.com

[David Green]

Maybe you could view it either way, although I think going the other
way around would make more sense only if the names were Order::Lower,
::Same, ::Higher.
S03 matches the old cmp semantics in that "3<=>4" returns -1, which
represents increasing order because reading left-to-right, we go from
3 up to 4.

However, what I'm wondering is whether Order::Same is "but true" and
the others "but false"? (Which makes cmp in boolean context the same
as eqv, but it seems to make sense that way.)

-David

[Larry Wall]

On Thu, Aug 17, 2006 at 11:27:21AM -0600, David Green wrote:
: However, what I'm wondering is whether Order::Same is "but true" and

: the others "but false"? (Which makes cmp in boolean context the same
: as eqv, but it seems to make sense that way.)

We should not be encouraging people to use cmp to mean eq. All that will
do is result in Great Confusion.

Larry

[Larry Wall]

I don't know if I've made this clear, but over the last few years I've
been treating "but True" and "but False" as design smells. They're
fine as a workaround for dire circumstances and uncooperative types,
but you'll not find me designing very many of the core interfaces to
use them, or other run-time mixins, for that matter. Solutions involving
"but" will generally be rejected, in other words.

Larry

[Alexey A. Kirithun]

On Thursday 17 August 2006 21:27, David Green wrote:

> However, what I'm wondering is whether Order::Same is "but true" and
> the others "but false"? (Which makes cmp in boolean context the same
> as eqv, but it seems to make sense that way.)

OTOH, C programmers can as well assume 'cmp' being an equivalent of '! eqv' in
boolean context; after all that's how strcmp() works... The same goes for
assembly programmers.

(* goes back lurking *)

--
Alexey A. Kiritchun