On Friday, September 23, 2016 at 4:13:53 AM UTC-4, Christoph Ortner wrote: > > The sum of an empty set or vector is undefined it is not zero. > >> you can rewrite it in a more explicit way >> >>> >>> > Actually a sum over an empty set is normally defined to be zero while a > product over an empty set is normally defined to be one >
More precisely, the empty sum and product are the additive and multiplicative identities, respectively. However, if you are summing something whose element type is unknown (Any), then the additive identity is also unknown (zero(Any) is undefined), and so sum(Any[]) is undefined (and throws an error).
