Sequence

A sequence is an ordered but non-indexed collection of objects. Operations add, remove, and get objects from the ends of a sequence or at a given Position. The container add operation adds to the right end and the remove operation splices out the element.

Positions generalize the idea of pointer into a sequence. A position can be obtained at the start or end of a sequence, or for the current position of an iterator. An element can be added at a position, pushing the elements to the right or left to make room. The element at a position can be retrieved or removed. Finally, a sequence can return the next or previous position from a given position.

• Sequence_CircList
  A circular doubly-linked list of elements. Only works for pointer types.
• Sequence_Linked
  A simple doubly-linked list of elements. Only works for pointer types.

• add : Sequence . T . Position . int push_dir -> void
  Adds the element at the position, pushing the current element toward the front (push_dir = -1) or back (push_dir = 1).
• add_extreme : Sequence . T . int side -> void
  Adds the element at the front (side = -1) or back (side = 1).
• advance : Sequence . Position . int dir -> Position
  Returns the position next to the given position in the given direction: toward the front (dir = -1) or back (side = 1).
• extreme : Sequence . int side -> T
  Returns the element at the front (side = -1) or back (side = 1).
• new_iterator : Sequence . int dir -> Iterator
  Returns an iterator initialized to proceed from back to front (dir = -1) or front to back (dir = 1).
• new_iterator : Sequence . Position . int dir -> Iterator
  Allocates and returns an iterator initialized to proceed from the position to front (dir = -1) or to back (dir = 1). The receiver is responsible for deallocation.
• new_position : Sequence . int side -> Position
  Returns the position for the front (side = -1) or back (side = 1) of the sequence.
• remove : Sequence . Position -> void
  Removes the element at the position, closing the hole. The position should not be used after this operation.
• remove_extreme : Sequence . int side -> void
  Removes the element at the front (side = -1) or back (side = 1).
• retrieve : Sequence . Position -> T
  Returns the element at the position in the sequence, which must be valid.
• valid : Sequence . Position -> bool
  Indicates whether or not the position references a member of the sequence.