/**
  * Copyright (c): Uwe Schmidt, FH Wedel
  *
  * You may study, modify and distribute this source code
  * FOR NON-COMMERCIAL PURPOSES ONLY.
  * This copyright message has to remain unchanged.
  *
  * Note that this document is provided 'as is',
  * WITHOUT WARRANTY of any kind either expressed or implied.
  */

/**
  *
  * f(i) = f1(i+1) - f1(i)
  */

//--------------------

public
class Diff extends Sequence {
  private
  long last;

  private
  Sequence s;

  public
  Diff(Sequence s) {
    this.s    = s;
    this.last = s.next();
  }

  public
  long next() {
    long i0 = last;

    last = s.next();

    return last - i0;
  }
}

//--------------------