Week1 Videos

In the first week Martine spoke about the importance of Reactive Programming, I suggest you to watch the videos of the course (Principles of Reactive Programming).

Code for video: Recap: Functions and Pattern Matching

In this video there is an implementation of a Json parser with case classes, and a show methods, one possible implementation in clojure is:

	(ns week1.jsonExample)
	(def data
	{:firstName "John",
	:lastName "Smith",
	:address {
	:streetAddress "21 2nd Stree",
	:state "NY",
	:postalCode 10021
	}
	:phoneNumbers [
	{:type "home" :number "212 555-1234"}
	{:type "fax" :number "646 555-4567"}
	]
	})
	; Utility Functions
	(defn pretty_str [s] (str "\"" s "\""))
	(defn comma_interposed_str [l] (apply str (interpose ", " l)))
	(defn folded_str [[s e] l] (str s (comma_interposed_str l) e))
	(def folded_list_str (partial folded_str "[]"))
	(def folded_map_str (partial folded_str "{}"))
	; Show implementation in clojure as multi methods
	(defmulti pretty_json type)
	(defmethod pretty_json clojure.lang.PersistentHashMap
	[m]
	(folded_map_str
	(map (fn [[k v]]
	(str (pretty_str (name k)) ":" (pretty_json v)))
	(seq m)) ))
	(defmethod pretty_json clojure.lang.PersistentVector
	[s]
	(folded_list_str (map pretty_json s)))
	(defmethod pretty_json String [e] (pretty_str e))
	(defmethod pretty_json nil [n] "null")
	(defmethod pretty_json :default [s] (str s))

view raw json.clj hosted with ❤ by GitHub

Here I used a simple Map with Json inside, the show method is pretty_json, instead of match I used multi function.

Code for video: Functional Random Generators

In this video Martin introduce the idea of functional generators to use for tests made with ScalaCheck, we will use clojurecheck that is a property base testing framework like ScalaCheck.

The code of generators is:

	(ns week1.generators
	(import [java.util Random]))
	(defn integers_gen [] (.nextInt (Random.)))
	(defn booleans_gen [] (> 0 (integers_gen)))
	(defn pairs_gen [] (take 2 (repeatedly integers_gen)))
	(defn choose_gen [lo hi] (+ lo (mod (integers_gen) (- hi lo))))
	(defn oneOf_gen [& cs] (nth cs (choose_gen 0 (count cs))))

view raw generators.clj hosted with ❤ by GitHub

I jumped the two recap video on language because I think that who came on this blog is a clojure developer, but if you want I can make a little tutorial on clojure.