Combine range of numbers.

the_0ne has asked for the wisdom of the Perl Monks concerning the following question:

Hi Monks, I know my title is vague, but I thought I'd let the actual content speak for itself. Here's what I want to do. I want to take this...

1,2,3,5,6,7,10,12,13,14,15

and turn it into this

1-3,5-7,10,12-15

I do have code and it works, however it just doesn't look perlish to me. I've always thought of regexes as basicly "can do anything with text". I tried a few and they just failed miserably. Here is my code...

#! /usr/bin/perl

use strict;

my $pages = "1,2,3,5,6,7,10,12,13,14,15";
my @pages_arr = split ',', $pages;
my (@return_arr, $next_one, $lower_bound, $upper_bound);

@return_arr = ();
$next_one = '';
$lower_bound = '';  $upper_bound = '';
for (my $x = 0; $x < scalar(@pages_arr); $x++) {
  $next_one = $pages_arr[$x];

  if ($x == 0) {
    $lower_bound = $upper_bound = $next_one;
  } elsif ($next_one == ($upper_bound + 1)) {
    $upper_bound = $next_one;
    if ($x == (scalar(@pages_arr) - 1)) {
      push @return_arr, "${lower_bound}-${upper_bound}";
    }
  } elsif ($next_one != ($upper_bound + 1)) {
    if ($lower_bound == $upper_bound) {
      push @return_arr, $lower_bound;
    } else {
      push @return_arr, "${lower_bound}-${upper_bound}";
    }

    $lower_bound = $upper_bound = $next_one;

    if ($x == (scalar(@pages_arr) - 1)) { push @return_arr, $next_one;
+ }
  }
}

my $return_var = join ',', @return_arr;
print "return_var:  ${return_var}\n";
[download]

It just looks so un-perlish. It does work and so far I haven't found a combination that breaks it. (The reason I say that is because this is part of a larger script that formats the input from the user like that. So, the numbers will always be in order and comma-delimited before it gets to that chunk of code.) However, it just looks like way too much code to do something so trivial. I won't ask if there is a better way, because Perl wouldn't be Perl if there wasn't. I'd just like to see what other Monks would do with this problem.

Thanks Monks.

Comment on Combine range of numbers. Download Code

Replies are listed 'Best First'.
Re: Combine range of numbers. by cees (Curate) on Jan 31, 2004 at 04:46 UTC
This was a question on the perl quiz of the week that ran for a few months last year. Question #6 asks exactly what you are looking for. Here is MJDs summary. The shortest solution was provided by Andreas Koenig: `use Set::IntSpan; # CPAN rules :-) use strict; sub expand_number_list { my $run = shift; my $set = Set::IntSpan->new($run); $set->elements; }` [download] Here is a list of everyone else's submisions. Update: Silly me, I included Andreas' answer for expand_number_list by mistake! Here is the one you are looking for: `use Set::IntSpan; # CPAN rules :-) use strict; sub format_number_list { my(@n) = @_; my $set = Set::IntSpan->new(join ",", @n); my $run = $set->run_list; $run =~ s/,/, /g; # give them the spaces $run; }` [download]	[reply] [d/l] [select]
Re: Re: Combine range of numbers. by the_0ne (Pilgrim) on Jan 31, 2004 at 04:56 UTC
Thanks cees, I'll check those out.	[reply]
Re: Combine range of numbers. by japhy (Canon) on Jan 31, 2004 at 04:36 UTC
I direct you to a node by me. It solves the problem with a regex. _____________________________________________________ Jeff`[japhy]`Pinyan: Perl, regex, and perl hacker, who'd like a job (NYC-area) `s++=END;++y(;-P)}y js++=;shajsj<++y(p-q)}?print:??;`	[reply]
Re: Re: Combine range of numbers. by the_0ne (Pilgrim) on Jan 31, 2004 at 04:54 UTC
Dude (mouth drops open) that is amazing... the_0ne bows humbly to japhy	[reply]
Re: Combine range of numbers. by jweed (Chaplain) on Jan 31, 2004 at 04:34 UTC
You might want to check out Consolidate Sequential Number Runs, which contains several fine links, and Super Search to find your answer. I left some lovely gems out there for you to find. C'mon. All the cool kids are doing it... Code is (almost) always untested. http://www.justicepoetic.net/	[reply]
Re: Re: Combine range of numbers. by the_0ne (Pilgrim) on Jan 31, 2004 at 04:51 UTC
Thanks jweed, my mind keeps thinking "print range", since we are using this for pages in documents, that I didn't search for number range or sequential numbers. :( Thanks for the reply.	[reply]


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