private TreeDictionary <TKey, TValue, TComparer> UpdateHelper(
TKey key, Func <TValue, Optional <TValue> > updateFunc, out Optional <TValue> value, out bool needRebalance)
{
if (Count == 0)
{
value = Optional <TValue> .None;
needRebalance = false;
return(this);
}
int comparison = _Comparer.Compare(key, _key);
if (comparison == 0)
{
value = _value;
var newValue = updateFunc(_value);
needRebalance = !newValue.HasValue;
return(needRebalance
? GlueBalanced(_left, _right)
: ReplaceValue(newValue.Value));
}
if (comparison < 0)
{
var newLeft = _left.UpdateHelper(key, updateFunc, out value, out needRebalance);
return(needRebalance
? NearlyBalanced(newLeft, _right)
: Balanced(newLeft, _right));
}
else
{
var newRight = _right.UpdateHelper(key, updateFunc, out value, out needRebalance);
return(needRebalance
? NearlyBalanced(_left, newRight)
: Balanced(_left, newRight));
}
}
