Class: Stupidedi::Zipper::MemoizedCursor

Inherits:
AbstractCursor show all
Defined in:
lib/stupidedi/zipper/memoized_cursor.rb

Instance Attribute Summary collapse

Querying the Tree Location collapse

Traversing the Tree collapse

Editing the Tree collapse

Instance Method Summary collapse

Methods inherited from AbstractCursor

#append_child, #between, #child, #children, #dangle, #depth, #descendant, #down, #first?, #flatten, #insert_left, #insert_right, #last?, #prepend_child, #root

Constructor Details

#initialize(node, path, parent) ⇒ MemoizedCursor

Returns a new instance of MemoizedCursor.



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# File 'lib/stupidedi/zipper/memoized_cursor.rb', line 17

def initialize(node, path, parent)
  @node, @path, @parent =
    node, path, parent
end

Instance Attribute Details

#node ⇒ #leaf?, ... (readonly)

Returns:



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# File 'lib/stupidedi/zipper/memoized_cursor.rb', line 8

def node
  @node
end

#path ⇒ Hole (readonly)

Returns:



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# File 'lib/stupidedi/zipper/memoized_cursor.rb', line 11

def path
  @path
end

Instance Method Details

#append(node) ⇒ EditedCursor

Returns:



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# File 'lib/stupidedi/zipper/memoized_cursor.rb', line 89

def append(node)
  EditedCursor.new(node,
    Hole.new(@node.cons(@path.left), @path.parent, @path.right), @parent)
end

#delete ⇒ EditedCursor

Returns:



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# File 'lib/stupidedi/zipper/memoized_cursor.rb', line 106

def delete
  if not last?
    # Move to `next`
    head, *tail = @path.right

    EditedCursor.new(head,
      Hole.new(@path.left, @path.parent, tail), @parent)
  elsif not first?
    # Move to `prev`
    head, *tail = @path.left

    EditedCursor.new(head,
      Hole.new(tail, @path.parent, @path.right), @parent)
  else
    # Deleting the only child
    parent =
      @parent.node.copy(:children =>
        @path.left.reverse.concat(@path.right))

    EditedCursor.new(parent, @path.parent, @parent.parent).dangle
  end
end

#first ⇒ MemoizedCursor

Returns:



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# File 'lib/stupidedi/zipper/memoized_cursor.rb', line 74

def first
  @parent.down
end

#last ⇒ MemoizedCursor

Returns:



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# File 'lib/stupidedi/zipper/memoized_cursor.rb', line 79

def last
  current = self
  current = current.next until current.last?
  current
end

#leaf? ⇒ Boolean

True if the node has no children

Returns:

  • (Boolean) 


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# File 'lib/stupidedi/zipper/memoized_cursor.rb', line 26

def leaf?
  @node.leaf? or @node.children.empty?
end

#next ⇒ MemoizedCursor

Returns:



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# File 'lib/stupidedi/zipper/memoized_cursor.rb', line 44

def next
  @__next ||= begin
    if last?
      raise Exceptions::ZipperError,
        "cannot move to next after last node"
    end

    head, *tail = @path.right

    MemoizedCursor.new(head,
      Hole.new(@node.cons(@path.left), @path.parent, tail), @parent)
  end
end

#prepend ⇒ EditedCursor

Returns:



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# File 'lib/stupidedi/zipper/memoized_cursor.rb', line 95

def prepend
  EditedCursor.new(node,
    Hole.new(@path.left, @path.parent, @node.cons(@path.right)), @parent)
end

#prev ⇒ MemoizedCursor

Returns:



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# File 'lib/stupidedi/zipper/memoized_cursor.rb', line 59

def prev
  @__prev ||= begin
    if first?
      raise Exceptions::ZipperError,
        "cannot move to prev before first node"
    end

    head, *tail = @path.left

    MemoizedCursor.new(head,
      Hole.new(tail, @path.parent, @node.cons(@path.right)), @parent)
  end
end

#replace(node) ⇒ EditedCursor

Returns:



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# File 'lib/stupidedi/zipper/memoized_cursor.rb', line 101

def replace(node)
  EditedCursor.new(node, @path, @parent)
end

#root? ⇒ Boolean

True if the node has no parent

Returns:

  • (Boolean) 


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# File 'lib/stupidedi/zipper/memoized_cursor.rb', line 31

def root?
  false
end

#up ⇒ AbstractCursor

Returns:



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# File 'lib/stupidedi/zipper/memoized_cursor.rb', line 39

def up
  @parent
end