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