def concat element, index
      raise IndexError, 'Expected new unique index' if @index.include? index

      @index |= [index]
      @data[@index[index]] = element

      update_position_cache
    end
def concat element, index
      raise IndexError, 'Expected new unique index' if @index.include? index

      @index |= [index]
      @data[@index[index]] = element

      update_position_cache
    end
def concat element , index raise IndexError , 'Expected new unique index' if @index . include? index @index |= [ index ] @data [ @index [ index ] ] = element update_position_cache end
Append an element to the vector by specifying the element and index
Append an element to the vector by specifying the element and index