NAME

       Attean::TreeRewriter - Walk and rewrite subtrees

VERSION

       This document describes Attean::TreeRewriter version 0.012

SYNOPSIS

         use v5.14;
         use Attean;
         my $w = Attean::TreeRewriter->new();
         my ($rewritten, $tree) = $w->rewrite($tree, $thunk);
         if ($rewritten) {
               ...
         }

DESCRIPTION

       The Attean::TreeRewriter class walks the nodes of query trees and rewrites sub-trees based on handlers
       that have been registered prior to rewriting.

ROLES

       None.

METHODS

       "register_pre_handler( \&code )"
           Register a handler that will be called for each sub-tree during tree rewriting.

           The function will be called as "&code( $tree, $parent_node, $thunk )" where $thunk is an opaque value
           passed to "rewrite".

           The function must return a list "($handled, $descend, $rewritten)".  $handled is a boolean indicating
           whether  the  handler  function  rewrote  the sub-tree, which is returned as $rewritten. The $descend
           boolean value indicates whether the the tree rewriting should continue downwards in the tree.

       "rewrite( $tree, $thunk, \%seen, $parent )"
           Rewrites the given $tree using the registered handler functions.  $thunk is passed  through  to  each
           handler  function.  %seen is currently unused.  $parent is passed through to the handler functions as
           the value of the pseudo-parent tree node for $tree.

           Returns a list "($handled, $tree)" with $handled indicating whether rewriting was performed, with the
           corresponding rewritten $tree.

BUGS

       Please  report  any   bugs   or   feature   requests   to   through   the   GitHub   web   interface   at
       <https://github.com/kasei/attean/issues>.

SEE ALSO

       <http://www.perlrdf.org/>

AUTHOR

       Gregory Todd Williams  "<gwilliams@cpan.org>"

COPYRIGHT

       Copyright  (c)  2014--2016 Gregory Todd Williams.  This program is free software; you can redistribute it
       and/or modify it under the same terms as Perl itself.

perl v5.22.1                                       2016-02-04                          Attean::TreeRewriter(3pm)