// <numeric> 
template <class InputIterator,
    class OutputIterator>
    OutputIterator adjacent_difference (
        InputIterator first,
        InputIterator last,
        OutputIterator result );
template <class InputIterator,
    class OutputIterator,
    class BinaryOperation>
    OutputIterator adjacent_difference (
        InputIterator first,
        InputIterator last,
        OutputIterator result,
        ​BinaryOperation binary_op );

计算算输出相邻元素的差值。