It's not totally clear to me what you mean by 'conflicts', and I think that there are probably several plausible meanings. For example, suppose change A says to add 100 lines of text at certain position, and change B does not. It that a conflict? Probably not, but perhaps, depending on what's in your mind. Similarly, suppose change A says to replace the text at lines 10-20 with a certain paragraph and change B says to add the same paragraph at line 21 without removing lines 10-20 first. Is that a conflict? I'm not sure.

Anyway, with the disclaimer, here is a subroutine that produces a list of conflicts between two diffs: 

sub conflicts {
  my ($a, $b) = @_;
  my ($ai, $bi) = (0,0);
  my @conflicts;
  while (defined $a->[$ai] && defined $b->[$bi]) {
    my ($ac, $bc) = ($a->[$ai], $b->[$bi]);

    # high and low line numbers for chunks a and b
    my ($al, $ah) = ($ac->[0][1], $ac->[-1][1]);
    my ($bl, $bh) = ($bc->[0][1], $bc->[-1][1]);

    if ($ah < $bl) {       # chunk a precedes chunk b
      ++$ai;
    } elsif ($al > $bh) {  # chunk a follows chunk b
      ++$bi;
    } else {               # chunks overlap
      # compare the two chunks for conflicts
      my %h;
      for my $line (@$ac) {
        my ($s, $ln, $t) = @$line;
        $h{$ln}{$s} = $t;
      }
      for my $line (@$bc) {
        my ($s, $ln, $t) = @$line;
        next unless exists $h{$ln};
        if (exists $h{$ln}{$s} && $h{$ln}{$s} ne $t) {
          push @conflicts,
            [[$s, $ln, $h{$ln}{$s}], 
             [$s, $ln, $t]];
        }
      }

      ++$ai; ++$bi;
    }
  }
  return @conflicts;
}

[download]
In list context, it returns a list of the conflicting sections. In scalar context, it returns the number of conflicts, which you can also use as a boolean.

This function interprets two insertions of different text at the same place to be a conflict, or two deletions of different text at the same place to be a conflict. If one diff deletes text at a position and the other inserts new text at the same place, that's not a conflict.

If that isn't what you want, the place to change it is probably the inner for my $line (@$bc) loop. At this point, the subroutine has located two overlapping sets of changes. (Non-overlapping sets of changes obviously can't be in conflict.) Change set A has been stored in the hash %h and the loop is looping over the changes in change set B to see if any of them conflict with the changes in A. By altering the tests inside this loop, you'll change the notion of 'conflict'.

Hope this helps.

In reply to Re: Question about Algorithm::Diff by Dominus
in thread Question about Algorithm::Diff by vroom

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