4.4: Vector Implementation

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The vector we've already seen has a perfectly adequate implementation to be a Bidirectional List. All we need to do is add the extra member functions to it and its iterator; the old ones don't have to change.

type Vector<item-type>
  ... # already-existing data and methods

Implement this in terms of the original insert-after() method. After that runs, we have to adjust iter's index so that it still refers to the same element.

  method insert(iter:Bidirectional List Iterator<item-type>, new-item:item-type)
    insert-after(new Vector-Iterator(iter.array, iter.index-1))
    iter.move-next()
  end method

Also implement this on in terms of an old function. After remove-after() runs, the index will already be correct.

  method remove(iter:Bidirectional List Iterator<item-type>)
    remove-after(new Vector-Iterator(iter.array, iter.index-1))
  end method
end type