Method firstOf

src/main/java/org/sfj/PegLegParser.java:787–818

Core PEG rule "Choice", here called firstOf. Tries each sub rule in turn, return first match. @param objs rules/string literals/char literals/execs @return rule

(Object... objs)

   * @return rule
   */
  public ParentRule firstOf(Object... objs) {
    List<Step> steps = asSteps(objs);
    PegLegRule<V> rule;
    if (steps.size() == 1 && steps.get(0).isRule()) {
      rule = steps.get(0).asRule();
    } else {
      rule = () -> {
        get().pushFrame("firstOf()");
        SingleNode<V> values = get().saveValues();
        int cnt = get().frameDepth();
        for (Step r : steps) {
          if (r.isRule()) {
            get().pushFrame();
            RuleReturn<V> ret = r.asRule().rule();
            if (ret.matched()) {
              get().trimFramesTo(cnt);
              return get().ruleReturn(true, true);
            }
            get().resetToLastFrame();
          } else {
            if (!r.asExec().exec()) {
              get().rollback(cnt, values);
              return get().ruleReturn(false, false);
            }
          }
        }
        get().rollback(cnt, values);
        return get().ruleReturn(false, false);
      };
    }
    return new ParentRule(rule);
  }

  /**
   * Core PEG Rule, "Test" returns true if sequence of rules matches, but does not consume input.