1 #!/usr/bin/env python 2 3 class Branch: 4 def __init__(self, nodes): 5 self.nodes = nodes 6 7 def visit(self, visitor): 8 return visitor.visitBranch(self) 9 10 class Leaf: 11 def __init__(self, value): 12 self.value = value 13 14 def visit(self, visitor): 15 return visitor.visitLeaf(self) 16 17 class Visitor: 18 def visit(self, node): 19 return node.visit(self) 20 21 # Visitor-specific functionality. 22 23 def visitBranch(self, node): 24 sum = 0 25 for node in node.nodes: 26 sum += self.visit(node) 27 return sum 28 29 def visitLeaf(self, node): 30 return node.value 31 32 tree = \ 33 Branch(( 34 Branch(( 35 Leaf(10), 36 Leaf(5) 37 )), 38 Leaf(2) 39 )) 40 41 visitor = Visitor() 42 result_17 = visitor.visit(tree) 43 44 # vim: tabstop=4 expandtab shiftwidth=4
