XXX: comment ranges method code

[perl/list-index.git] / lib / List / Index.pm

diff --git a/lib/List/Index.pm b/lib/List/Index.pm
index 50e48a5eb30f71d6b3abaefe77bcbd2a09b9cfa7..574613e8b1c38e2e6b3eaf4c751fd42d53c6930e 100644 (file)
--- a/lib/List/Index.pm
+++ b/lib/List/Index.pm
@@ -28,12 +28,15 @@ sub ranges {
        while ($offset < @$self) {
                my $link = substr $self->[$offset], 0, $length;
                if ($context) {
-                       my $trim = 1;
+                       # take a value slightly before the current offset
                        my $before = $offset > $context ? $self->[$offset - $context] : '.';
+                       # see how much of it matches the current link
+                       my $trim = 1;
                        for my $match (split //, $before) {
                                scalar $link =~ /\G\Q$match/g or last;
                                $trim++;
                        }
+                       # truncate link upto where the earlier value starts to differ
                        substr($link, $trim) = '' unless $trim > length $link;
                }
 
@@ -45,9 +48,11 @@ sub ranges {
                my ($link, $lastchar) = $links[$i + 1]->[0] =~ /(.*)(.)/;
                $link .= $lastchar eq 'a' ? '.' : chr( ord($lastchar) - 1 )
                        unless $lastchar eq '.';
+               next if $link eq $links[$i]->[0] and $i;
                $links[$i]->[1] = $link;
        }
        $links[-1]->[1] = '';
+       $links[0]->[0] = '';
 
        return \@links;
 }