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Postings from November 2003
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Moin,
[youvegotpost.de? Denglish Alert!]
An einem sonnigen Herbstdienstag, Michael schrieb:
> On 2003-11-04 10:49:14 Dave Mitchell <davem@fdgroup.com> was overheard
>saying:
>> On Mon, Nov 03, 2003 at 12:37:49PM -0800, Michael Jacob wrote:
>>>
>>> I think, this change should not break any well written module. Testing
>>> for any method that's in UNIVERSAL is just useless, we already know
>>> before the test that it must be there. Any module that want's to know if
>>> there is some additional method in UNIVERSAL:: can just test against
>>> UNIVERSAL->can() directly.
>>
>>But C<can> doesn't just test for existance, it returns a code ref of the
>>method if found. Thus C<$code = $obj->can('can')> is perfectly
>>reasonable, and should return a ref to UNIVERSAL::can if there aren't
>>any others in the inheritance chain.
>
>Show me one CPAN module that calls can() on anything (other than UNIVERSAL)
> to get a coderef for can(), isa() or VERSION().
I didn't know that it returns a code ref. BigInt has code like:
if $CALC->can('_add') { ... do something }
Now, caching the lookup might give us a tad more speed, but as show below
caching the test makes it twice as fast, while caching the actual code-ref
doesn't makes it only a further 20% faster...
So, I could live with can() only returning true.
te@null:~/perl/spams> perl bench.pl
Benchmark: running cache, can, has for at least 5 CPU seconds...
cache: 6 s (5.39 usr + 0.01 sys = 5.40 CPU) @ 1543282/s (n=8333726)
can: 5 s (5.29 usr + 0.00 sys = 5.29 CPU) @ 632335/s (n=3345056)
has: 4 s (5.05 usr + 0.00 sys = 5.05 CPU) @ 1281006/s (n=6469083)
te@null:~/perl/spams> cat bench.pl
#!/usr/bin/perl -w
package Test;
sub test { return $_[0]; }
package main;
use Benchmark;
my $CALC = 'Test';
my $has; $has->{test} = $CALC->can('test');
timethese ( -5,
{
can => sub { $CALC->test(0) if $CALC->can('test'); },
has => sub { $CALC->test(0) if $has->{test}; },
cache => sub { &{$has->{test}}(0) if $has; },
} );
Best wishes,
Tels
- --
Signed on Tue Nov 4 15:23:05 2003 with key 0x93B84C15.
Visit my photo gallery at http://bloodgate.com/photos/
PGP key on http://bloodgate.com/tels.asc or per email.
"We have problems like this all of the time," Kirk said, trying to
reassure me. "Sometimes its really hard to get things burning." --
http://tinyurl.com/qmg5
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