Antlr4.Runtime.Misc.IntervalSet.Add C# (CSharp) Method

        protected internal virtual void Add(Interval addition)
        {
            if (@readonly)
            {
                throw new InvalidOperationException("can't alter readonly IntervalSet");
            }
            //System.out.println("add "+addition+" to "+intervals.toString());
            if (addition.b < addition.a)
            {
                return;
            }
            // find position in list
            // Use iterators as we modify list in place
            for (int i = 0; i < intervals.Count; i++)
            {
                Interval r = intervals[i];
                if (addition.Equals(r))
                {
                    return;
                }
                if (addition.Adjacent(r) || !addition.Disjoint(r))
                {
                    // next to each other, make a single larger interval
                    Interval bigger = addition.Union(r);
                    intervals[i] = bigger;
                    // make sure we didn't just create an interval that
                    // should be merged with next interval in list
                    while (i < intervals.Count - 1)
                    {
                        i++;
                        Interval next = intervals[i];
                        if (!bigger.Adjacent(next) && bigger.Disjoint(next))
                        {
                            break;
                        }
                        // if we bump up against or overlap next, merge
                        intervals.RemoveAt(i);
                        // remove this one
                        i--;
                        // move backwards to what we just set
                        intervals[i] = bigger.Union(next);
                        // set to 3 merged ones
                    }
                    // first call to next after previous duplicates the result
                    return;
                }
                if (addition.StartsBeforeDisjoint(r))
                {
                    // insert before r
                    intervals.Insert(i, addition);
                    return;
                }
            }
            // if disjoint and after r, a future iteration will handle it
            // ok, must be after last interval (and disjoint from last interval)
            // just add it
            intervals.Add(addition);
        }

 public void TestMixedRangesAndElements()
 {
     IntervalSet s = new IntervalSet();
     s.Add(1);
     s.Add('a', 'z');
     s.Add('0', '9');
     String expecting = "{1, 48..57, 97..122}";
     Assert.AreEqual(s.ToString(), expecting);
 }