[OT] Re: [performance/benchmark] printing techniques

[Perrin Harkins <pe...@primenet.com>]

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

Re: [OT] Re: [performance/benchmark] printing techniques

[Mike Lambert <mi...@home.com>]

> 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

Re: [OT] Re: [performance/benchmark] printing techniques

[Matt Sergeant <ma...@sergeant.org>]

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

[Perrin Harkins <pe...@primenet.com>]

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

[Matt Sergeant <ma...@sergeant.org>]

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