code: public DoubleStreamEx intersperse(int delimiter) {
          return new DoubleStreamEx(stream().flatMap(s -> DoubleStreamEx.of(delimiter, s)).skip(1), context);
      }
docs: Returns a new stream containing all the elements of the original stream interspersed with
  given delimiter.
  
  <p>
  For example, {@code DoubleStreamEx.of(1, 2, 3).intersperse(4)} will yield a stream containing
  five elements: 1, 4, 2, 4, 3.
  
  <p>
  This is an <a href="package-summary.html#StreamOps">intermediate operation</a>.
  
  @param delimiter a delimiter to be inserted between each pair of elements
  @return the new stream
  @since 0.6.6