Method alternate

java/com/google/re2j/Parser.java:276–294

()

  // alternate replaces the top of the stack (above the topmost '(') with its
  // alternation.
  private Regexp alternate() {
    // Scan down to find pseudo-operator (.
    // There are no | above (.
    Regexp[] subs = popToPseudo();

    // Make sure top class is clean.
    // All the others already are (see swapVerticalBar).
    if (subs.length > 0) {
      cleanAlt(subs[subs.length - 1]);
    }

    // Empty alternate is special case
    // (shouldn't happen but easy to handle).
    if (subs.length == 0) {
      return push(newRegexp(Regexp.Op.NO_MATCH));
    }

    return push(collapse(subs, Regexp.Op.ALTERNATE));
  }

  // cleanAlt cleans re for eventual inclusion in an alternation.
  private void cleanAlt(Regexp re) {