From: Mr Hash <[EMAIL PROTECTED]>
> On 03/26, Jenda Krynicky said something like:
> > From: "Jonathan E. Paton" <[EMAIL PROTECTED]>
> > > > affect the performance of:
> > > > key listings (things like grep /pattern/, keys %hash)
> > >
> > > Grep can be slow, especially with patterns. Keys
> > > could be slow, especially if the dataset is large.
> >
> > Maybe you could try to use
> >
> > while (my ($key) = each %hash) {
> > next unless $key =~ /pattern/
> > ... do whatever you need
> > }
>
> Hmm. I used grep thinking it would be fast. I'll try iterating the
> keys and having a good simple regex, too.
It IS pretty fast. But it you have lots of keys and do
@good_keys = grep /pattern/, keys %hash;
or even
@keys = keys %hash;
You force Perl to create a huge array for you.
I'm not sure what will Perl do if you
foreach my $good_key (grep /pattern/, keys %hash) {
whether it'll create the temporary list or will behave "lazily" and grep
through the keys as you need them, but I'd expect the first.
Jenda
=========== [EMAIL PROTECTED] == http://Jenda.Krynicky.cz ==========
There is a reason for living. There must be. I've seen it somewhere.
It's just that in the mess on my table ... and in my brain
I can't find it.
--- me
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