Velocity Reviews - Computer Hardware Reviews

Velocity Reviews > Newsgroups > Programming > Perl > Perl Misc > FAQ 4.47 How do I handle circular lists?

Reply
Thread Tools

FAQ 4.47 How do I handle circular lists?

 
 
PerlFAQ Server
Guest
Posts: n/a
 
      04-06-2011
This is an excerpt from the latest version perlfaq4.pod, which
comes with the standard Perl distribution. These postings aim to
reduce the number of repeated questions as well as allow the community
to review and update the answers. The latest version of the complete
perlfaq is at http://faq.perl.org .

--------------------------------------------------------------------

4.47: How do I handle circular lists?

(contributed by brian d foy)

If you want to cycle through an array endlessly, you can increment the
index modulo the number of elements in the array:

my @array = qw( a b c );
my $i = 0;

while( 1 ) {
print $array[ $i++ % @array ], "\n";
last if $i > 20;
}

You can also use "Tie::Cycle" to use a scalar that always has the next
element of the circular array:

use Tie::Cycle;

tie my $cycle, 'Tie::Cycle', [ qw( FFFFFF 000000 FFFF00 ) ];

print $cycle; # FFFFFF
print $cycle; # 000000
print $cycle; # FFFF00

The "Array::Iterator::Circular" creates an iterator object for circular
arrays:

use Array::Iterator::Circular;

my $color_iterator = Array::Iterator::Circular->new(
qw(red green blue orange)
);

foreach ( 1 .. 20 ) {
print $color_iterator->next, "\n";
}



--------------------------------------------------------------------

The perlfaq-workers, a group of volunteers, maintain the perlfaq. They
are not necessarily experts in every domain where Perl might show up,
so please include as much information as possible and relevant in any
corrections. The perlfaq-workers also don't have access to every
operating system or platform, so please include relevant details for
corrections to examples that do not work on particular platforms.
Working code is greatly appreciated.

If you'd like to help maintain the perlfaq, see the details in
perlfaq.pod.
 
Reply With Quote
 
 
 
Reply

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Re: How include a large array? Edward A. Falk C Programming 1 04-04-2013 08:07 PM
Possible to handle web requests without an ASPX page? i.e. have DLL handle request. jdlwright@shaw.ca ASP .Net 2 05-31-2005 05:42 PM
Semi-circular definitions (plus circular references) Kiuhnm C++ 16 01-03-2005 03:49 AM
how to handle command line output(not terminal handle) Leon Python 2 11-04-2004 05:16 AM
File Handle Reading Blues: Rereading a File Handle for Input Dietrich Perl 1 07-22-2004 10:02 AM



Advertisments