Re: [OT] Re: [performance/benchmark] printing techniques
On Thu, 8 Jun 2000, Perrin Harkins wrote:
On Thu, 8 Jun 2000, Matt Sergeant wrote:
The one that bugs me is when I see people doing this:
$hash{"$key"}
instead of this:
$hash{$key}
Those two now also result in the same code. ;-)
But the former is just ugly.
Sometimes it's worse than just ugly. See the entry in the Perl FAQ:
http://www.perl.com/pub/doc/manual/html/pod/perlfaq4.html#What_s_wrong_with_always_quoting
Not likely that anyone would be using something as a hash key that would
suffer from being stringified, but possible. It's definitely a bit slower
as well, but that's below the noise level.
It's not slower in 5.6. "$x and $y" in 5.6 gets turned into $x . ' and '
. $y (in perl bytecode terms).
--
Matt/
Fastnet Software Ltd. High Performance Web Specialists
Providing mod_perl, XML, Sybase and Oracle solutions
Email for training and consultancy availability.
http://sergeant.org http://xml.sergeant.org
Re: [OT] Re: [performance/benchmark] printing techniques
It's not slower in 5.6. "$x and $y" in 5.6 gets turned into $x . ' and ' . $y (in perl bytecode terms). that's not new to 5.6.0, variable interpolation in ""'s has always turned into a concat tree, though 5.005_03 is the oldest version i have handy to check with. and, this "$feature" can be quite expensive.
Re: [OT] Re: [performance/benchmark] printing techniques
On Wed, 7 Jun 2000, Perrin Harkins wrote:
On Wed, 7 Jun 2000, Matt Sergeant wrote:
On Wed, 7 Jun 2000, Eric Cholet wrote:
This said, i hurry back to s/"constant strings"/'constant strings'/g;
Those two are equal.
Yes, although it's counter-intutive there's no real performance hit
from double-quoting constant strings.
The one that bugs me is when I see people doing this:
$hash{"$key"}
instead of this:
$hash{$key}
Those two now also result in the same code. ;-)
But the former is just ugly.
--
Matt/
Fastnet Software Ltd. High Performance Web Specialists
Providing mod_perl, XML, Sybase and Oracle solutions
Email for training and consultancy availability.
http://sergeant.org http://xml.sergeant.org
Re: [OT] Re: [performance/benchmark] printing techniques
On Thu, 8 Jun 2000, Matt Sergeant wrote:
The one that bugs me is when I see people doing this:
$hash{"$key"}
instead of this:
$hash{$key}
Those two now also result in the same code. ;-)
But the former is just ugly.
Sometimes it's worse than just ugly. See the entry in the Perl FAQ:
http://www.perl.com/pub/doc/manual/html/pod/perlfaq4.html#What_s_wrong_with_always_quoting
Not likely that anyone would be using something as a hash key that would
suffer from being stringified, but possible. It's definitely a bit slower
as well, but that's below the noise level.
- Perrin
Re: [OT] Re: [performance/benchmark] printing techniques
Sometimes it's worse than just ugly. See the entry in the Perl FAQ:
http://www.perl.com/pub/doc/manual/html/pod/perlfaq4.html#What_s_wrong_with_
always_quoting
Not likely that anyone would be using something as a hash key that would
suffer from being stringified, but possible. It's definitely a bit slower
as well, but that's below the noise level.
Actually, when you use a reference as a hash key, it is automatically
stringified anyway.
http://www.perl.com/pub/doc/manual/html/pod/perlfaq4.html#How_can_I_use_a_re
ference_as_a_h
So that means that: $hash{"$key"} and $hash{$key}differ only in the relative
merits of their beauty. :)
Mike Lambert
[OT] Re: [performance/benchmark] printing techniques
On Wed, 7 Jun 2000, Matt Sergeant wrote:
On Wed, 7 Jun 2000, Eric Cholet wrote:
This said, i hurry back to s/"constant strings"/'constant strings'/g;
Those two are equal.
Yes, although it's counter-intutive there's no real performance hit
from double-quoting constant strings.
The one that bugs me is when I see people doing this:
$hash{"$key"}
instead of this:
$hash{$key}
That one is actually in the perlfaq man page, but I still see it all the
time. The performance difference is very small but it does exist, and you
can get unintended results from stringifying some things.
- Perrin
