Beefy Boxes and Bandwidth Generously Provided by pair Networks
We don't bite newbies here... much
 
PerlMonks  

Re: Regular expressions and sort

by Perl Mouse (Chaplain)
on Nov 04, 2005 at 14:31 UTC ( [id://505712]=note: print w/replies, xml ) Need Help??


in reply to Regular expressions and sort

To answer your question: yes, that is normal behaviour. $1 and friends are only set on a succesful match - if the match fails, $1 and friends keep their value. You could do:
$am = $1 if $_[0] =~ /$mask/; $bm = $1 if $_[1] =~ /$mask/;
Or, to avoid warnings:
($am, $bm) = map {/$mask/ ? $1 : 0} @_;

Having said that, I always try to avoid using a sort-sub, and often a sort-block as well. Instead, I would opt for a GRT in this case:

@result = map {substr $_, 2} sort map {sprint "%02d%s", (/$mask/ ? $1 : 0), $_} @f;
Using a GRT means you do the extraction of the key you want to sort on only once per element, instead of once per comparison. If you have to sort a long array, this can be significant.
Perl --((8:>*

Log In?
Username:
Password:

What's my password?
Create A New User
Domain Nodelet?
Node Status?
node history
Node Type: note [id://505712]
help
Chatterbox?
and the web crawler heard nothing...

How do I use this?Last hourOther CB clients
Other Users?
Others sharing their wisdom with the Monastery: (7)
As of 2024-03-28 21:37 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?

    No recent polls found