Half Journey

Today is exactly the middle of my Batch at Recurce Center. Six weeks has passed and I just realized that I learned some stuff, but I have still much to learn here.

I just set for myself the objectives for the rest of the my Batch which will be to try to contribute to a OSS project while continuing to learn Clojure.

My plan is to post about what I learn (and my findings) but trying to avoid keeping too personal.

So what I learned today?

Resources for Closure

The list below is a must have favorites links for every person how would like to learn Clojure or plans to use it.

• Grimoire: A Cheatsheet of many Clojure functions presented in a nice way!
• ClojureDocs: Is the community-powered documentation and examples repository.
• Clojure Werkz A growing collection of open source Clojure libraries

Closures

What are they? What does it mean to have a Closure?

First, the definition by wikipedia:

In programming languages, closures (also lexical closures or function closures) are a technique for implementing lexically scoped name binding in languages with first-class functions. Operationally, a closure is a data structure storing a function together with an environment.

An example, implementing Power of function using Closures.

(defn pow [initial]
  (fn [x] (reduce * (repeat initial x))))

Calling the code above in the REPL:

user=> ((pow 2) 3)
9
user=> ((pow 6) 3)
729
user=> ((pow 3) 3)
27

So what just happened? We created a function which returns another function which happens to have an initial value stored on it’s instance in the memory.

I am not sure yet, but I can say that the initial variable, is now a “private attribute” of the instance of function pow which gets in the run time.

It seems a very powerful resource!