Source/Fusion/Core/ObservableList/SumTree.Operations.cs
/// <summary>
/// Get the prefix sum up to (but not including) index. O(log n).
/// </summary>
Get the prefix sum up to (but not including) index.
Get the prefix sum up to ( but not including ) index .
public T Sum(int index)
		{
			if (index < 0 || index > Count)
				throw new IndexOutOfRangeException("index");
			return _tree.MatchWith(
				tree => SumInner(0, tree, Count, index),
				() => _unit);
		}
public T Sum ( int index ) { if ( index < 0 || index > Count ) throw new IndexOutOfRangeException ( " " ) ; return _tree . MatchWith ( tree => SumInner ( 0 , tree , Count , index ) , ( ) => _unit ) ; }
Get the prefix sum up to (but not including) index.
Get the prefix sum up to ( but not including ) index .
index
int