| 1 | """ |
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| 2 | Iterate Through Recursive Data With Yield |
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| 3 | |
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| 4 | If you study the _scanInOrder method below you will see that implementing it with `yield` is very |
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| 5 | straightforward. Without `yield` the alternative is to write a helper class that implements |
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| 6 | IEnumerator<of T> and maintains state variables to track its current position in between calls to |
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| 7 | .moveNext. Yuck! |
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| 8 | |
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| 9 | This example was adapted from http://msdn.microsoft.com/msdnmag/issues/06/00/C20/default.aspx |
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| 10 | """ |
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| 11 | |
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| 12 | |
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| 13 | class Node<of T> where T must be IComparable<of T> |
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| 14 | |
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| 15 | cue init(item as T) |
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| 16 | .init(item, nil, nil) |
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| 17 | |
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| 18 | cue init(item as T, left as Node<of T>?, right as Node<of T>?) |
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| 19 | base.init |
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| 20 | _item = item |
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| 21 | _left = left |
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| 22 | _right = right |
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| 23 | |
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| 24 | pro left from var as Node<of T>? |
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| 25 | |
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| 26 | pro right from var as Node<of T>? |
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| 27 | |
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| 28 | get item from var as T |
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| 29 | |
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| 30 | def compareTo(node as Node<of T>) as int |
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| 31 | # this method enables comparison operators in Cobra like "a < b" where a and b are Nodes |
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| 32 | return .item.compareTo(node.item) |
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| 33 | |
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| 34 | def toString as String is override |
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| 35 | return '[.typeOf.name](item=[.item])' |
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| 36 | |
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| 37 | def dump |
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| 38 | print this stop |
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| 39 | if _left, print ' left:', _left stop |
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| 40 | if _right, print ' right:', _right stop |
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| 41 | print |
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| 42 | if _left, _left.dump |
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| 43 | if _right, _right.dump |
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| 44 | |
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| 45 | |
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| 46 | class BinaryTree<of T> where T must be IComparable<of T> |
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| 47 | |
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| 48 | cue init(root as Node<of T>) |
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| 49 | base.init |
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| 50 | _root = root |
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| 51 | |
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| 52 | pro root from var as Node<of T> |
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| 53 | |
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| 54 | def add(items as vari T) |
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| 55 | for item in items, .add(item) |
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| 56 | |
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| 57 | def add(item as T) |
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| 58 | _add(Node<of T>(item), _root) |
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| 59 | |
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| 60 | def _add(newNode as Node<of T>, root as Node<of T>) |
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| 61 | if newNode > root |
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| 62 | right = root.right |
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| 63 | if right |
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| 64 | _add(newNode, right) |
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| 65 | else |
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| 66 | root.right = newNode |
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| 67 | else if newNode < root |
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| 68 | left = root.left |
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| 69 | if left |
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| 70 | _add(newNode, left) |
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| 71 | else |
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| 72 | root.left = newNode |
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| 73 | |
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| 74 | get inOrder as IEnumerable<of T> |
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| 75 | return _scanInOrder(_root, 0) |
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| 76 | |
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| 77 | def _scanInOrder(node as Node<of T>?, level) as IEnumerable<of T> |
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| 78 | if node |
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| 79 | if node.left |
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| 80 | for item in _scanInOrder(node.left to !, level+1) |
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| 81 | yield item |
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| 82 | yield node.item |
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| 83 | if node.right |
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| 84 | for item in _scanInOrder(node.right to !, level+1) |
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| 85 | yield item |
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| 86 | |
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| 87 | |
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| 88 | class Program |
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| 89 | |
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| 90 | def main |
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| 91 | tree = BinaryTree<of int>(Node<of int>(0)) |
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| 92 | tree.add(4, 6, 2, 7, 5, 3, 1) |
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| 93 | values = List<of int>() |
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| 94 | for value in tree.inOrder |
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| 95 | # print value |
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| 96 | values.add(value) |
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| 97 | assert values == [0, 1, 2, 3, 4, 5, 6, 7] |
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