Class: Stupidedi::Zipper::StackCursor

Inherits:
AbstractCursor show all
Defined in:
lib/stupidedi/zipper/stack_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

#child, #children, #depth, #descendant, #first?, #flatten, #insert_left, #insert_right, #last?, #root

Constructor Details

#initialize(node, path, parent) ⇒ StackCursor

Returns a new instance of StackCursor.



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# File 'lib/stupidedi/zipper/stack_cursor.rb', line 20

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/stack_cursor.rb', line 11

def node
  @node
end

#parent ⇒ AbstractCursor (readonly)

Returns:



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# File 'lib/stupidedi/zipper/stack_cursor.rb', line 18

def parent
  @parent
end

#path ⇒ Hole (readonly)

Returns:



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

def path
  @path
end

Instance Method Details

#append(node) ⇒ EditedCursor, void

Insert a new sibling node after (to the right of) the current node, and navigate to the new sibling node

Returns:



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# File 'lib/stupidedi/zipper/stack_cursor.rb', line 109

def append(node)
  if root?
    raise Exceptions::ZipperError,
      "root node has no siblings"
  end

  replace(node)
end

#append_child(child) ⇒ Object 



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# File 'lib/stupidedi/zipper/stack_cursor.rb', line 133

def append_child(child)
  StackCursor.new(child, Hole.new([], @path, []), self)
end

#between(other) ⇒ Object

Raises:



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# File 'lib/stupidedi/zipper/stack_cursor.rb', line 45

def between(other)
  raise Exceptions::ZipperError,
    "stack cursor doesn't support this method"
end

#copy(changes = {}) ⇒ Object 



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

def copy(changes = {})
  StackCursor.new \
    changes.fetch(:node, @node),
    changes.fetch(:path, @path),
    changes.fetch(:parent, @parent)
end

#dangle ⇒ Object 



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# File 'lib/stupidedi/zipper/stack_cursor.rb', line 154

def dangle
  if leaf?
    StackCursor.new(nil, Hole.new([], @path, []), self)
  else
    head, *tail = @node.children

    unless tail.empty?
      raise Exceptions::ZipperError,
        "stack cursor doesn't support nodes with multiple children"
    end

    StackCursor.new(head, Hole.new([], @path, []), self)
  end
end

#delete ⇒ EditedCursor, void

Remove the current node, and navigate to the next (rightward) node if one exists. Otherwise, navigate to the previous (leftward) node if one exists. Otherwise, create a placeholder where the next sibling node will be created.

Returns:



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# File 'lib/stupidedi/zipper/stack_cursor.rb', line 145

def delete
  if root?
    raise Exceptions::ZipperError,
      "cannot delete root node"
  end

  @parent
end

#down ⇒ MemoizedCursor

Navigate to the first child node

Returns:



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# File 'lib/stupidedi/zipper/stack_cursor.rb', line 88

def down
  if leaf?
    raise Exceptions::ZipperError,
      "cannot descend into leaf node"
  end

  head, *tail = @node.children

  unless tail.empty?
    raise Exceptions::ZipperError,
      "stack cursor doesn't support nodes with multiple children"
  end

  StackCursor.new(head, Hole.new([], @path, []), self)
end

#first ⇒ AbstractCursor

Navigate to the first (leftmost) sibling node

Returns:



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# File 'lib/stupidedi/zipper/stack_cursor.rb', line 54

def first
  self
end

#last ⇒ AbstractCursor

Navigate to the last (rightmost) sibling node

Returns:



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

def last
  self
end

#leaf? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/stupidedi/zipper/stack_cursor.rb', line 36

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

#next ⇒ AbstractCursor, void

Navigate to the next (rightward) sibling node

Returns:



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# File 'lib/stupidedi/zipper/stack_cursor.rb', line 65

def next
  raise Exceptions::ZipperError,
    "stack cursor doesn't maintain siblings"
end

#prepend(node) ⇒ EditedCursor, void

Insert a new sibling node before (to the left of) the current node, and navigate to the new sibling node

Returns:



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# File 'lib/stupidedi/zipper/stack_cursor.rb', line 120

def prepend(node)
  if root?
    raise Exceptions::ZipperError,
      "root node has no siblings"
  end

  replace(node)
end

#prepend_child(child) ⇒ Object 



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# File 'lib/stupidedi/zipper/stack_cursor.rb', line 129

def prepend_child(child)
  StackCursor.new(child, Hole.new([], @path, []), self)
end

#prev ⇒ AbstractCursor, void

Navigate to the previous (leftward) sibling node

Returns:



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# File 'lib/stupidedi/zipper/stack_cursor.rb', line 72

def prev
  raise Exceptions::ZipperError,
    "stack cursor doesn't maintain siblings"
end

#replace(node) ⇒ AbstractCursor, RootCursor

Replace the current node with the given node

Returns:



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# File 'lib/stupidedi/zipper/stack_cursor.rb', line 139

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

#root? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/stupidedi/zipper/stack_cursor.rb', line 41

def root?
  @path.root?
end

#up ⇒ AbstractCursor

Navigate to the parent node

Returns:



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# File 'lib/stupidedi/zipper/stack_cursor.rb', line 78

def up
  if root?
    raise Exceptions::ZipperError,
      "root node has no siblings"
  end

  @parent
end