| #!/usr/bin/ruby |
| # encoding: utf-8 |
| |
| =begin LICENSE |
| |
| [The "BSD licence"] |
| Copyright (c) 2009-2010 Kyle Yetter |
| All rights reserved. |
| |
| Redistribution and use in source and binary forms, with or without |
| modification, are permitted provided that the following conditions |
| are met: |
| |
| 1. Redistributions of source code must retain the above copyright |
| notice, this list of conditions and the following disclaimer. |
| 2. Redistributions in binary form must reproduce the above copyright |
| notice, this list of conditions and the following disclaimer in the |
| documentation and/or other materials provided with the distribution. |
| 3. The name of the author may not be used to endorse or promote products |
| derived from this software without specific prior written permission. |
| |
| THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
| IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
| OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. |
| IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, |
| INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
| NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
| THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| |
| =end |
| |
| module ANTLR3 |
| module AST |
| |
| =begin rdoc ANTLR3::AST::Visitor |
| |
| AST::Visitor is an extra utility class for working with tree objects. Visitor |
| objects are similar to plain vanilla iterators, but provide two action hooks, |
| instead a standard single iteration block. The <tt>visit(tree)</tt> method walks |
| through each node of the tree (top-down left-to-right). If +pre_action+ is |
| defined, a node is yielded to the block when it has been initially entered. If |
| +post_action+ is defined, a node is yielded to the block after all of its |
| children have been visited. |
| |
| =end |
| |
| class Visitor |
| def initialize( adaptor = nil ) |
| @adaptor = adaptor || CommonTreeAdaptor.new() |
| @pre_action = nil |
| @post_action = nil |
| block_given? and yield( self ) |
| end |
| |
| def pre_action( &block ) |
| block_given? and @pre_action = block |
| return @pre_action |
| end |
| |
| def post_action( &block ) |
| block_given? and @post_action = block |
| return @post_action |
| end |
| |
| def visit( tree, pre_action = nil, post_action = nil ) |
| flat = @adaptor.flat_list?( tree ) |
| before = pre_action || @pre_action |
| after = post_action || @post_action |
| |
| tree = before.call( tree ) unless before.nil? or flat |
| @adaptor.child_count( tree ).times do |index| |
| child = @adaptor.child_of( tree, index ) |
| visit( child, pre_action, post_action ) |
| end |
| tree = after.call( tree ) unless after.nil? or flat |
| |
| return tree |
| end |
| end |
| end |
| end |