I assume many of you are used to doing logic programming in perl but this is new to me. I wrote up a simple optree-recursing (this won't work in practice because of NULL nodes) expression which finds a given node in a tree and returns the path required to reach it. Is there a common way to write a more plausible implementation of $ROOT->(parent|sibling)* $target that doesn't require a regex to handle all the bookkeeping of tracking successes, failures and to-do work?

sub path_to_op
{
    my ( $root, $tgt ) = @_;

    local $op = $root;
    local @path;

    '' =~
        /(?:
            (?(?{ my $name = $op->oldname;
                  local $op = $op->parent;
                  local @path = ( @path, "$name/" ); })(?=)|(?!))
            |
            (?(?{ my $name = $op->oldname;
                  local $op = $op->sibling;
                  local @path = ( @path, "...," ); })(?=)|(?!))
         ) *

         (?(?{ $$op == $$tgt })(?=)|(?!)) /x;

    @path;
}

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In reply to Logic programming without using the RE engine as a crutch by diotalevi

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