private TreeDictionary <TKey, TValue, TComparer> UnionTrim(
TreeDictionary <TKey, TValue, TComparer> otherDict,
TKey low, TKey high,
Func <TKey, TValue, TValue, TValue> combiner)
{
if (otherDict.Count == 0)
{
return(this);
}
if (Count == 0)
{
var otherLeft = otherDict._left.FilterLess(high);
var otherRight = otherDict._right.FilterGreater(low);
return(ReferenceEquals(otherDict._left, otherLeft) && ReferenceEquals(otherDict._right, otherRight)
? otherDict
: otherDict.Unbalanced(otherDict._value, otherLeft, otherRight));
}
Debug.Assert(_Comparer.Compare(low, _key) < 0 && _Comparer.Compare(high, _key) > 0);
return(Unbalanced(
_value,
_left.UnionTrim(otherDict.Trim(low, _key), low, _key, combiner),
_right.UnionTrim(otherDict.Trim(_key, high), _key, high, combiner)));
}