each_with_object

        # Enumerator.each_with_object

(from ruby core)
---
    e.each_with_object(obj) {|(*args), obj| ... }
    e.each_with_object(obj)
    e.with_object(obj) {|(*args), obj| ... }
    e.with_object(obj)

---

Iterates the given block for each element with an arbitrary object,
`obj`, and returns `obj`

If no block is given, returns a new Enumerator.

### Example

    to_three = Enumerator.new do |y|
      3.times do |x|
        y << x
      end
    end

    to_three_with_string = to_three.with_object("foo")
    to_three_with_string.each do |x,string|
      puts "#{string}: #{x}"
    end

    # => foo: 0
    # => foo: 1
    # => foo: 2