Logically it can be expressed as operating on the set {1, 2, 3, 4, 5} - I think that's the point: one can perceive it differently, either as a set operation or as a loop/iteration.

  module Numeric
    def times(&b)
      (1..self).each(&b)
    end
  end

It's really no different than the Scala you'd write for the same thing:

  implicit class LongHelpers(l: Long) {
    def times(f: => Any) = (1L to l) foreach f
  }

  10 times println("here's a line!")

To interpret that as a Set operation would make the definition of a Set operation so broad as to be useless IMO.

sets aren't ordered

The set of ordered sets is a subset of the set of sets. Totally ordered sets, which I think are synonymous with chains(?), are still sets.

But yes, I was talking loosely: my point was to differentiate between a mental model of iterating over a sequence (or ordered set) and applying a set-like transformation. My mental picture was of a field formed by a matrix operation on a limited space as being composed of the summation of a series of vector transformations; my maths language doesn't really allow me to properly describe it however. Loosely: you can break down a [subset of] 3D transformation[s] of a surface in to a series of 2D transformations performed iteratively, or you can apply a 3D transformation; they're different mental images of acquiring the same result.