2 - Two interfaces

Sequence Interface

given $n$ items in an order $(x_0,x_1,...,x_{n-1})=X$ ($X$ is often called an iterable) We must support the following:

• Container:
  • build(X) - build a sequence from items in X.
  • len() - return the number of stored items.
• Static:
  • iter_seq() - return stored items in sequence order.
  • get_at(i) - return the item at index $i$.
    -set_at(i,x) - replace the item at index $i$ with $x$.
• Dynamic:
  -insert_at(i,x) - add $x$ as the item with index $i$.
  • insert_first(x) -add $x$ as the first item.
  • insert_last(x) -add $x$ as the last item.
  • delete_at(i) - remove and return the item at index $i$.
  • delete_first() remove and return the first item.
  • delete_last() remove and return the last item.