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Contents?: true
Size: 1.77 KB
Versions: 22
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Stored size: 1.77 KB
Contents
module BookKeeping
VERSION = 71
end
Node = Struct.new(:value, :left, :right)
Crumb = Struct.new(:direction, :value, :tree)
class Zipper
attr_reader :value
def initialize(value, left, right, crumbs=[])
@value = value
@left = left
@right = right
@crumbs = crumbs
end
def self.from_tree(tree)
Zipper.new(tree.value, tree.left, tree.right)
end
def to_tree
tree = Node.new(value, @left, @right)
for crumb in @crumbs
case crumb.direction
when :left
tree = Node.new(crumb.value, tree.dup, crumb.tree)
when :right
tree = Node.new(crumb.value, crumb.tree, tree.dup)
end
end
tree
end
def left
return nil if @left.nil?
crumbs = [Crumb.new(:left, value, @right)] + @crumbs
Zipper.new(@left.value, @left.left, @left.right, crumbs)
end
def right
return nil if @right.nil?
crumbs = [Crumb.new(:right, value, @left)] + @crumbs
Zipper.new(@right.value, @right.left, @right.right, crumbs)
end
def up
crumb = @crumbs.first
return nil if crumb.nil?
remaining_crumbs = @crumbs.drop(1)
case crumb.direction
when :left
Zipper.new(crumb.value,
Node.new(value, @left, @right),
crumb.tree,
remaining_crumbs)
when :right
Zipper.new(crumb.value,
crumb.tree,
Node.new(value, @left, @right),
remaining_crumbs)
end
end
def set_value(new_value)
Zipper.new(new_value, @left, @right, @crumbs)
end
def set_left(node)
Zipper.new(value, node, @right, @crumbs)
end
def set_right(node)
Zipper.new(value, @left, node, @crumbs)
end
def ==(other_zipper)
return false unless other_zipper.is_a? Zipper
to_tree == other_zipper.to_tree
end
end
Version data entries
22 entries across 22 versions & 1 rubygems