v

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type Tree = Empty | Node
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struct Empty {}
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struct Node {
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	value int
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	left  Tree
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	right Tree
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}
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// Note: a match expression, infers the type of its result
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// from the type of the return value in the first branch,
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// => it needs an explicit int(0) cast here:
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fn size(tree Tree) int {
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	return match tree {
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		Empty { int(0) }
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		Node { 1 + size(tree.left) + size(tree.right) }
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	}
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}
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fn main() {
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	node1 := Node{30, Empty{}, Empty{}}
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	node2 := Node{20, Empty{}, Empty{}}
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	tree := Node{10, node1, node2}
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	println('tree structure:\n ${tree}')
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	println('tree size: ${size(tree)}')
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}
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