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# Let's define a Tree
Tree = Algebrick.type do |tree|
variants Empty = atom,
Leaf = type { fields Integer },
Node = type { fields tree, tree }
end # => Tree(Empty | Leaf | Node)
# Now types `Tree(Empty | Leaf | Node)`, `Empty`, `Leaf(Integer)` and `Node(Tree, Tree)` are defined.
# Let's add a method, don't miss the **pattern matching** example.
module Tree
# compute depth of a tree
def depth
match self,
(on Empty, 0),
(on Leaf, 1),
# ~ will store and pass matched parts to variables left and right
(on Node.(~any, ~any) do |left, right|
1 + [left.depth, right.depth].max
end)
end
end
# Method defined in module `Tree` are passed down to **all** values of type Tree.
Empty.depth # => 0
Leaf[10].depth # => 1
Node[Leaf[4], Empty].depth # => 2
Node[Empty, Node[Leaf[1], Empty]].depth # => 3
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