Shortcut for running this SourceTOut, TMat with a reduce function. The given function is invoked for every received element, giving it its previous output (from the second element) and the element as input. The returned TaskTResult will be completed with value of the final function evaluation when the input stream ends, or completed with Failure if there is a failure signaled in the stream.

public Task<TOut> RunSum(
	Func<TOut, TOut, TOut> reduce,
	IMaterializer materializer
)

member RunSum : 
        reduce : Func<'TOut, 'TOut, 'TOut> * 
        materializer : IMaterializer -> Task<'TOut>