Iterates in reverse a specified number of times and returns the new iterator position.
template<class BidirectionalIterator>
  BidirectionalIterator prev(
    BidirectionalIterator _First,
    typename iterator_traits<BidirectionalIterator>::difference_type
        _Off = 1
    );
Parameters
- _First 
 The current position.
- _Off 
 The number of times to iterate.
Property Value/Return Value
Returns the new iterator position after iterating _Off times.
Remarks
The template function returns next decremented off times.
Requirements
Header: <iterator>
Namespace: std