STL -- Standard Template Library
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Provides a set of easily composable C++ container classes and generic algorithms.

Container classes include 
  -- vector 
  -- lists
  -- stack 
  -- queue 
  -- deque (double-ended q),
  -- set (item is in once) 
  -- multiset (allows duplicate items)  
  -- priority queue,
  -- map (mapping of a unique key/value pair)
  -- multimap (multiple copies of a key)

Iterators for the containers include forward, bidirectional, random access.
They include (although not all have all) the common operations of <, >, etc.

The generic algorithms include many common tasks, e.g., searching, sorting,
merging, copying, etc.

Iterators
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Definition -- a software design pattern that abstracts the process of 
              traversing through a collection of items

Note -- vector[i] or array[i] can be considered as a primitive iterator

An iterator should include 
  -- Current position 
  -- Retrieval of the current item
  -- Stepping to the next position (forward or backward)