Yeah, but remember to pass the 0 to it; otherwise the sum of an empty array would be nil:

  x.inject(0, &:+)

That's one of the disadvantages of not having a powerful type system to infer what's the "zero" of some type.

Still, the Ruby code is pretty readable and a good example of orthogonal concepts that compose well. E.g., getting the product of the numbers instead: x.inject(1, &:*). Or the least common multiple: x.inject(&:lcm).