1 #!/usr/bin/ruby 2 # encoding: utf-8 3 4 =begin LICENSE 5 6 [The "BSD licence"] 7 Copyright (c) 2009-2010 Kyle Yetter 8 All rights reserved. 9 10 Redistribution and use in source and binary forms, with or without 11 modification, are permitted provided that the following conditions 12 are met: 13 14 1. Redistributions of source code must retain the above copyright 15 notice, this list of conditions and the following disclaimer. 16 2. Redistributions in binary form must reproduce the above copyright 17 notice, this list of conditions and the following disclaimer in the 18 documentation and/or other materials provided with the distribution. 19 3. The name of the author may not be used to endorse or promote products 20 derived from this software without specific prior written permission. 21 22 THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 23 IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 24 OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 25 IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 26 INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 27 NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 28 DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 29 THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 30 (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 31 THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 32 33 =end 34 35 module ANTLR3 36 module AST 37 38 =begin rdoc ANTLR3::AST::Visitor 39 40 AST::Visitor is an extra utility class for working with tree objects. Visitor 41 objects are similar to plain vanilla iterators, but provide two action hooks, 42 instead a standard single iteration block. The <tt>visit(tree)</tt> method walks 43 through each node of the tree (top-down left-to-right). If +pre_action+ is 44 defined, a node is yielded to the block when it has been initially entered. If 45 +post_action+ is defined, a node is yielded to the block after all of its 46 children have been visited. 47 48 =end 49 50 class Visitor 51 def initialize( adaptor = nil ) 52 @adaptor = adaptor || CommonTreeAdaptor.new() 53 @pre_action = nil 54 @post_action = nil 55 block_given? and yield( self ) 56 end 57 58 def pre_action( &block ) 59 block_given? and @pre_action = block 60 return @pre_action 61 end 62 63 def post_action( &block ) 64 block_given? and @post_action = block 65 return @post_action 66 end 67 68 def visit( tree, pre_action = nil, post_action = nil ) 69 flat = @adaptor.flat_list?( tree ) 70 before = pre_action || @pre_action 71 after = post_action || @post_action 72 73 tree = before.call( tree ) unless before.nil? or flat 74 @adaptor.child_count( tree ).times do |index| 75 child = @adaptor.child_of( tree, index ) 76 visit( child, pre_action, post_action ) 77 end 78 tree = after.call( tree ) unless after.nil? or flat 79 80 return tree 81 end 82 end 83 end 84 end 85
