Module: Linked::Mutable

Included in:
Listable
Defined in:
lib/linked/mutable.rb

Overview

This module collects all the methods that mutate a listable item.

Instance Method Summary collapse

Instance Method Details

#append(object) ⇒ Object

rubocop:disable Metrics/MethodLength



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# File 'lib/linked/mutable.rb', line 8

def append(object)
  # Assume the given object to be the head of its chain
  # B. If it is not, chain B will be split before the
  # object, and the sub chain in which the object now is
  # the head will be appended.
  sub_chain_b_head = coerce object

  # Grab the first item in this chain. We will need it
  # later.
  target_chain = chain_head

  # Split chain B before the given object and grab the
  # tail of that new sub chain.
  sub_chain_b_tail = sub_chain_b_head.split_before_and_insert target_chain

  # If we are the last item in our chain we need to
  # notify the head that there is a new tail.
  # Otherwise the next item in the list need to be
  # linked up correctly.
  if chain_tail?
    target_chain.prev = sub_chain_b_tail
  else
    sub_chain_b_tail.next = next!
    next!.prev = sub_chain_b_tail
  end

  # Connect sub chain B to this item
  sub_chain_b_head.prev = self
  self.next = sub_chain_b_head

  sub_chain_b_tail
end

#delete ⇒ self

Remove an item from the chain. Note that calling #delete on the first item in a chain causes all subsequent items to be moved to a new chain.

Usage

Example using the chain A <> B <> C

A.delete # => A | B <> C
B.delete # => B | A <> C
C.delete # => C | A <> B

Returns:



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# File 'lib/linked/mutable.rb', line 83

def delete
  if chain_head?
    split_after_and_insert
  else
    shrink

    if chain_tail?
      chain_head.prev = @_prev
    else
      @_next.prev = @_prev
    end

    @_prev.next = @_next
  end

  reset_item
end

#delete_after ⇒ nil, Listable

Remove all items after this one in the chain.

Returns:

  • if this is the lst item.

  • the first item in the chain that was just deleted.



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# File 'lib/linked/mutable.rb', line 115

def delete_after
  return nil if chain_tail?

  item = next!
  item.split_before_and_insert
  item
end

#delete_before ⇒ nil, Listable

Remove all items before this one in the chain.

Returns:

  • if this is the first item.

  • the first item in the chain that was just deleted.



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# File 'lib/linked/mutable.rb', line 107

def delete_before
  prev!.split_after_and_insert unless chain_head?
end

#prepend(object) ⇒ Object

rubocop:disable Metrics/MethodLength



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# File 'lib/linked/mutable.rb', line 45

def prepend(object)
  sub_chain_a_tail = coerce object

  if chain_head?
    sub_chain_a_tail.split_after_and_insert
    sub_chain_a_tail.append self

    return chain_head
  end

  target_chain = chain_head

  sub_chain_a_head = sub_chain_a_tail.split_after_and_insert target_chain

  prev!.next = sub_chain_a_head
  sub_chain_a_head.prev = prev!

  sub_chain_a_tail.next = self
  self.prev = sub_chain_a_tail

  sub_chain_a_head
end