title: STD function to return the first iterator where a subsequence begins
body: <p>Is there a way to return a distance between the first iterator of a sequence, which yields the start of a subsequence in case it is contained within the sequence?</p>
  <p>I know <a href="https://en.cppreference.com/w/cpp/algorithm/includes" rel="nofollow noreferrer">there is</a> <code>std::includes</code> which returns <code>true</code> if a sequence is a subsequence of another. And it can take a <code>Compare</code> object.
  My first guess was to have an object to increment a captured iterator (inside a lambda) every time the start of a subsequence is found.
  But then I realized that both sequences must be sorted, and a <code>Compare</code> object must return <code>true</code> on <code>a &lt; b</code>.</p>
  <p>Can this be done using the std algorithms library?</p>