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62 lines
1.5 KiB
Ruby
62 lines
1.5 KiB
Ruby
# Represent an operation to be performed on the elements of an object structure.
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# Visitor lets a new operation be defined without changing the classes of the
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# elements on which it operates.
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module Node
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def accept visitor
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if self.kind_of? StringNode
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visitor.visit_string self if visitor.respond_to? :visit_string
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elsif self.kind_of? IntegerNode
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visitor.visit_int self if visitor.respond_to? :visit_int
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end
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end
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end
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class StringNode
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include Node
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attr_accessor :string
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def initialize(val)
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@string = val
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end
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end
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class IntegerNode
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include Node
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attr_accessor :int
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def initialize(val)
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@int = val
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end
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end
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class PrintingVisitor
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def visit_string(node)
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puts node.string
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end
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def visit_int(node)
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puts node.int
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end
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end
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class RevertingVisitor
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def visit_string(node)
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puts node.string.reverse!
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end
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end
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# Usage
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myTreeRoot = Tree::TreeNode.new("ROOT", StringNode.new("this is the root node"))
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myTreeRoot << Tree::TreeNode.new("child1", StringNode.new("madam im adam")) << Tree::TreeNode.new("grandchild1", IntegerNode.new(3)) << Tree::TreeNode.new("grandchild2", IntegerNode.new(2))
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myTreeRoot << Tree::TreeNode.new("child2", StringNode.new("race car")) <<Tree::TreeNode.new("grandchild3", StringNode.new("damn, i agassi miss again. mad"))
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puts "PRINTING visitor..."
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@pvisitor = PrintingVisitor.new
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myTreeRoot.each { |node| node.content.accept @pvisitor }
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puts "\nREVERTING visitor..."
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@rvisitor = RevertingVisitor.new
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myTreeRoot.each { |node| node.content.accept @rvisitor }
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