Fuzion • Idioms • Idiom # 16: Depth-first traversing of a binary tree

Idiom # 16: Depth-first traversing of a binary tree

Code

traverse (f T -> unit) unit =>
  match bin_tree.this
    nil           =>
    n Bin_Tree_Node =>
      n.left.traverse f
      f n.val
      n.right.traverse f

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traverse (f T -> unit) unit =>
  match bin_tree.this
    nil           =>
    n Bin_Tree_Node =>
      n.left.traverse f
      f n.val
      n.right.traverse f
 
 
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What are effects?

Running Example

# a Bin_Tree_Node is a value plus left and right sub-trees
#
Bin_Tree_Node(T type : property.orderable,
            val T,
            left, right bin_tree T) ref
is

  # add element to this tree, return resulting tree
  #
  add (v T) bin_tree T =>
    l := if (v < val) (left .add v) else left
    r := if (v > val) (right.add v) else right
    Bin_Tree_Node val l r


# a bin_tree is either a Bin_Tree_Node or an empty tree represented by nil
#
bin_tree(T type : property.orderable) : choice (Bin_Tree_Node T) nil is

  # add element to this tree, return resulting tree
  #
  add (v T) bin_tree T =>
    match bin_tree.this
      nil           => Bin_Tree_Node v nil nil
      n Bin_Tree_Node => n.add v

  # traverse this tree
  #
  traverse (f T -> unit) unit =>
    match bin_tree.this
      nil           =>
      n Bin_Tree_Node =>
        n.left.traverse f
        f n.val
        n.right.traverse f

for
  tree bin_tree String := nil, tree.add x
  x in ["dog", "elephant", "cat", "cat", "cat", "cat", "lion", "ant", "bee", "albatros", "hyena", "horse", "frog"]
else
  tree.traverse (s -> say s)

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# a Bin_Tree_Node is a value plus left and right sub-trees
#
Bin_Tree_Node(T type : property.orderable,
            val T,
            left, right bin_tree T) ref
is
  # add element to this tree, return resulting tree
  #
  add (v T) bin_tree T =>
    l := if (v < val) (left .add v) else left
    r := if (v > val) (right.add v) else right
    Bin_Tree_Node val l r
# a bin_tree is either a Bin_Tree_Node or an empty tree represented by nil
#
bin_tree(T type : property.orderable) : choice (Bin_Tree_Node T) nil is
  # add element to this tree, return resulting tree
  #
  add (v T) bin_tree T =>
    match bin_tree.this
      nil           => Bin_Tree_Node v nil nil
      n Bin_Tree_Node => n.add v
  # traverse this tree
  #
  traverse (f T -> unit) unit =>
    match bin_tree.this
      nil           =>
      n Bin_Tree_Node =>
        n.left.traverse f
        f n.val
        n.right.traverse f
for
  tree bin_tree String := nil, tree.add x
  x in ["dog", "elephant", "cat", "cat", "cat", "cat", "lion", "ant", "bee", "albatros", "hyena", "horse", "frog"]
else
  tree.traverse (s -> say s)
 
 
הההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההה
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What are effects?

last changed: 2024-07-01

next: Idiom # 17: Create a Tree data structure