Iterators

• Read starting on 535.
• Most container classes support iterators.
• They are an abstract method for accessing the elements of a container.
  • These are like pointers. (probably are pointers)
  • When working with the iterator i,
    • *i gives access to the entire object
    • i->element gives access to an individual field/member.
  • They support == and != comparisons.
  • They support ++ and --, += and most math.
• There are multiple types of iterators:
  • const or not
  • forward or reverse

  • vector<int> aVector;
    vector<int>::iterator i;   
    vector<int>::reverse_iterator r;
    vector<int>::const_iterator j;
    vector<int>::const_reverse_iterator k; 

• All container with iterators support
  • whatever.begin(): an iterator referencing the first item in the container
  • whatever.end() an iterator referencing one past the last item in the container.
  • whatever.rbegin() an iterator referencing the last item in the container.
  • whatever.rend() an iterator referencing one past the first item in the container.
• (I stole this from the web).
• Constant iterators have cbegin, cend, crbegin, crend.
• He mentions that there are functions begin(vector), end(vector) rbegin(vector)... in the STL
• Some warnings
  • Have the same problems as index and pointers with out container memory.
  • Don't mix across different containers.
  • Don't get carried away with math.
• So why iterators?
  • We need them for some vector functions
  • We need them for the standard algorithm library.
  • In some cases, they are far more efficient than []
• see iterators.cpp.