Exercises

The following sections have a few exercises for you.

Exercise 5.1

Extend our current EventStream implementation to include a function called take. It works much like Clojure's core take function for sequences: it will take n items from the underlying event stream after which it will stop emitting items.

A sample interaction, which takes the first five items emitted from the original event stream, is shown here:

(def es1 (from-interval 500))
(def take-es (take es1 5))

(subscribe take-es #(prn "Take values: " %))

;; "Take values: " 0
;; "Take values: " 1
;; "Take values: " 2
;; "Take values: " 3
;; "Take values: " 4

Tip

Keeping some state might be useful here. Atoms can help. Additionally, try to think of a way to dispose of any unwanted subscriptions required by the solution.

Exercise 5.2

In this exercise, we will add a function called zip that zips together items emitted from two different event streams into a vector.

A sample interaction with the zip function is as follows:

(def es1 ...