Attean::TreeRewriter3pm

Usage

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

Version

This document describes Attean::TreeRewriter version 0.035

Overview

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.