has method

bool has(E input)

Implementation

bool has(E input) {
  if (comparator(lower, upper) == 0) return lower == input;

  if (isAscending) {
    return comparator(input, lower) >= 0 && comparator(input, upper) < 0;
  } else {
    return comparator(input, upper) >= 0 && comparator(input, lower) < 0;
  }
}