Re: Is it ok to use "zero-but-true"?

[Dave Rolsky]

On Thu, 20 Jan 2005 [EMAIL PROTECTED] wrote:
DT::Set count() currently returns "undef" on error,
and "0" for empty sets.
Should it return "zero-but-true" (0e0) for empty sets?
No, this is just confusing.  What do you mean by "on error"?  Do you mean 
when a set is possibly infinite, and therefore uncountable?  In thise case 
undef is right, because the value truly is unknown.

If it's an actual input error, it should throw an exception.
-dave
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Re: Is it ok to use "zero-but-true"?

[Bruce Van Allen]

On 2005-01-20 [EMAIL PROTECTED] wrote:
>DT::Set count() currently returns "undef" on error, and "0" for empty
>sets.

>Should it return "zero-but-true" (0e0) for empty sets?

I use 0e0 (or '0 but true') in lots of cases where an empty set is a
valid return value, where zero is a valid index, and where zero is a
valid input datum not the same as that datum being "empty", all cases
where truth tests alone aren't sufficient to distinguish a real zero
from '', undef, etc.

But I've wondered: is zbt one of those charming Perlisms that, for all
its utility, might fall by the wayside or be shown to harbor potential
for serious errors?

>Such that you could write:
> $count = $set->count or die "can't count";
>instead of:
> $count = $set->count; die "can't count" unless defined $count;

I say this is an improvement, pending enlightenment on the above
question.

As always, Flavio, thanks for your good work.



- Bruce

__bruce__van_allen__santa_cruz__ca__

Is it ok to use "zero-but-true"?

[fglock]

DT::Set count() currently returns "undef" on error,
and "0" for empty sets.

Should it return "zero-but-true" (0e0) for empty sets?

Such that you could write:
  $count = $set->count or die "can't count";
instead of:
  $count = $set->count;
  die "can't count" unless defined $count;

- Flavio S. Glock


-- DT::Set POD ---
=item * count

Returns a count of C objects in the set.
..
when C operates on large recurrence sets, it
will return at most approximately C<200>. For larger
sets, and for I sets, C will
return C.

Please note that this is explicitly not a scalar
zero, since a zero count is a valid return value for
empty sets!
..
-

Re: Bug: DT::Event::Recurrence Modifies Params

[fglock]

Yitzchak wrote:
> 
> YMMV, but I find something like this more clear:
> 
> @args = sort { ($a < 0) <=> ($b < 0) || $a <=> $b }
@args;
> 
> (literally, sort first by positive/negative, then
by value).
> 

Very nice - thanks!

Actually, I'm planning to rewrite this part of the 
program, because it can't handle overflow cases like
this one:

  monthly ( days => [ 30, -20 ] )

- Flavio S. Glock