Class: Stupidedi::Zipper::EditedCursor

Inherits:
AbstractCursor show all
Defined in:
lib/stupidedi/zipper/edited_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) ⇒ EditedCursor

Returns a new instance of EditedCursor.



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# File 'lib/stupidedi/zipper/edited_cursor.rb', line 16

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

Instance Attribute Details

#node (readonly)

Returns the value of attribute node.



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

def node
  @node
end

#parent ⇒ AbstractCursor (readonly)

Returns:



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# File 'lib/stupidedi/zipper/edited_cursor.rb', line 14

def parent
  @parent
end

#path ⇒ Hole (readonly)

Returns:



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

def path
  @path
end

Instance Method Details

#append(node) ⇒ AbstractCursor, EditedCursor

Navigate to the last (rightmost) sibling node

Returns:



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# File 'lib/stupidedi/zipper/edited_cursor.rb', line 110

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

#delete ⇒ AbstractCursor, EditedCursor

Navigate to the last (rightmost) sibling node

Returns:



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# File 'lib/stupidedi/zipper/edited_cursor.rb', line 130

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 ⇒ AbstractCursor, EditedCursor

Navigate to the first (leftmost) sibling node

Returns:



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# File 'lib/stupidedi/zipper/edited_cursor.rb', line 81

def first
  if first?
    return self
  end

  right = @path.left.init.reverse.concat(@node.cons(@path.right))

  EditedCursor.new(@path.left.last,
    Hole.new([], @path.parent, right), @parent)
end

#last ⇒ AbstractCursor, EditedCursor

Navigate to the last (rightmost) sibling node

Returns:



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# File 'lib/stupidedi/zipper/edited_cursor.rb', line 94

def last
  if last?
    return self
  end

  left = @node.cons(@path.right.init.reverse).concat(@path.left)

  EditedCursor.new(@path.right.last,
    Hole.new(left, @path.parent, []), @parent)
end

#leaf?

True if the node has no children



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# File 'lib/stupidedi/zipper/edited_cursor.rb', line 25

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

#next ⇒ AbstractCursor, EditedCursor

Navigate to the next (rightward) sibling node

Returns:



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# File 'lib/stupidedi/zipper/edited_cursor.rb', line 53

def next
  if last?
    raise Exceptions::ZipperError,
      "cannot move to next after last node"
  end

  head, *tail = @path.right

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

#prepend(node) ⇒ AbstractCursor, EditedCursor

Navigate to the last (rightmost) sibling node

Returns:



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# File 'lib/stupidedi/zipper/edited_cursor.rb', line 117

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

#prev ⇒ AbstractCursor, EditedCursor

Navigate to the previous (leftward) sibling node

Returns:



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# File 'lib/stupidedi/zipper/edited_cursor.rb', line 67

def prev
  if first?
    raise Exceptions::ZipperError,
      "cannot move to prev before first node"
  end

  head, *tail = @path.left

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

#replace(node) ⇒ AbstractCursor, EditedCursor

Navigate to the last (rightmost) sibling node

Returns:



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# File 'lib/stupidedi/zipper/edited_cursor.rb', line 124

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

#root?

True if the node has no parent



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# File 'lib/stupidedi/zipper/edited_cursor.rb', line 30

def root?
  false
end

#up ⇒ AbstractCursor

Navigate to the parent node

Returns:



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

def up
  node =
    @parent.node.copy(:children =>
      @path.left.reverse.concat(@node.cons(@path.right)))

  if parent.root?
    RootCursor.new(node)
  else
    EditedCursor.new(node, @path.parent, @parent.parent)
  end
end