Re: [FWP] Formatting integer sets with ranges

[sthoenna@efn.org (Yitzchak Scott-Thoennes)]

In article <f9kd4gzkg+BG092yn@efn.org>, I wrote:
>I had to write a throwaway script to (among other things) print a
>sorted array of integers like 1,2,3,5,6,8,10 as a list of ranges like
>1-3,5-6,8,10.
[snip]

>but it seems like there should be a somewhat simpler way to do this
>(along the lines of "print map ...").  Any takers?

I came up with this, but I hate it:

my ($prev, $beg);
print map(!$prev ? ($beg = $prev = $_) :
          $_ == $prev+1 ? do {++$prev; ()} :
          do { my $xprev = $prev;
          (($beg != $xprev ? ('-', $xprev) : ()), ',',$beg = $prev = $_)},
          @issues),
      $beg != $prev ? ('-', $prev) : ();
print "\n";

The do { my $xprev stuff I needed to work around what seems like a perl bug.

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