static double[] diffsBetweenPairsOfDoubles(double[] l) {
  int n = l(l)/2;
  if (n < 1) ret emptyDoubleArray();
  double[] diffs = new[n];
  for i to n:
    diffs[i] = l[i*2]-l[i*2+1];
  ret diffs;
}

Began life as a copy of #1032702