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Could some please tell me what this code does?[solved]

otisphat80 (37)
Hello everyone I am reading Bjarne Stroustrups new book and i am having a hard time figuring out what this code does.The problem I have with it is 'while(n--)'
, the n++ I get but this is suppose to be an example of a forward iterator so how is he decrementing the index.Thanks
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  On the other hand, a forward iterator must get to the nth 
element by moving one step at a time (e.g.,
following links on a list):

  
  template<typename Iter>
  void advance_helper(Iter p, int n, forward_iterator_tag)
  {
      if (0<n)
        while (nāˆ’āˆ’) ++p;
      else if (n<0)
        while (n++) āˆ’āˆ’p;
  }
Last edited on
JLBorges (13770)
This is the helper function for std::advance() which increments given iterator it by n elements.

With this proviso:
If n is negative, the iterator is decremented. In this case, the iterator must meet the requirements of BidirectionalIterator, otherwise the behaviour is undefined. http://en.cppreference.com/w/cpp/iterator/advance

In other words, if n is positive, any InputIterator would do,
but if n is negative, the iterator must be a BidirectionalIterator.
otisphat80 (37)
Thank you.
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