```
template<class InputIterator, class OutputIterator>
constexpr OutputIterator
adjacent_difference(InputIterator first, InputIterator last,
OutputIterator result);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2>
ForwardIterator2
adjacent_difference(ExecutionPolicy&& exec,
ForwardIterator1 first, ForwardIterator1 last, ForwardIterator2 result);
template<class InputIterator, class OutputIterator, class BinaryOperation>
constexpr OutputIterator
adjacent_difference(InputIterator first, InputIterator last,
OutputIterator result, BinaryOperation binary_op);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2,
class BinaryOperation>
ForwardIterator2
adjacent_difference(ExecutionPolicy&& exec,
ForwardIterator1 first, ForwardIterator1 last,
ForwardIterator2 result, BinaryOperation binary_op);
```

Mandates:

- For the overloads with no ExecutionPolicy, T is constructible from *first. acc (defined below) is writable ([iterator.requirements.general]) to the result output iterator. The result of the expression binary_op(val, std::move(acc)) is writable to result.
- For the overloads with an ExecutionPolicy, the result of the expressions binary_op(*first, *first) and *first are writable to result.

Effects:
For the overloads with no ExecutionPolicy and a non-empty range,
the function creates an accumulator acc of type T,
initializes it with *first,
and assigns the result to *result.

For every iterator i in [first + 1, last) in order,
creates an object val whose type is T,
initializes it with *i,
computes binary_op(val, std::move(acc)),
assigns the result to *(result + (i - first)), and
move assigns from val to acc.