Iterators

• container iterators for(x.first(); x.good(); x.next()) process(x.current()); for(Elem * i = x.first(); i != 0; i = x.next()) process(*i);
  often used in OpenDoc

  
  

• STL iterators while( first != last ) process(*first++);

  
  

• natural iterators

Not-so-pleasant traits of the container/STL iterators

• have states

• potential danger
  
  • accessing an iterator when it is not good
  • process(*first) when first == last
    
  • solution with pointers: real danger

• inefficiency
  it takes a lot of trouble to make sure the iterator is safe to use:
  three checks in the container iterator

iterators are distinguished by very characteristic patterns

much is written about what's neat about iterators. There is a talk about STL iterators here at MacHack. Let me mention a few not-so-neat traits

For example, a container iteration has to check three times if x is still good:

• before entering the body of the loop
• in accessing the current element
• before attempting to advance the iterator

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