First impressions on Clojure

Has been 3 weeks that I’m learning Clojure. Here I will dedicate myself to putting posts about what I’m thinking of Clojure.
Beforehand I wanna make clear that this series is by the vision of a person that has never worked with a functional language and has never heard about LISP or his dialects. Keep in mind that the languages that I feel comfortable with (not expert) are Javascript, PHP, and Python. So, let’s go!

Learning resources (Occasionally change from time to time)

I think it’s worth sharing where I’m getting information about Clojure, will it help anyone?

Sites:
Alura Courses
Clojuredocs
Clojure repos
Clojure official website

Blogs:
vlaaad blog

REPL is good

Since I’m acquainted with other languages, I love the possibility to have a quick shell to clarify questions like:
Is it an empty python dict truthy?
What happens if I try to access an empty property of a PHP array? it will throw? will return null?

Things like REPL is good to programmers because we don’t need to memorize everything. And Clojure does this very well. The Clojure REPL is simply and fast as it should be. I remember that I was very happy when I find out about the Clojure REPL.

The only language that I feel uncomfortable with his REPL is Javascript.. You can say: “Oh we have node to act like a REPL” But the node does not have a window element, and also not all functions that we use in a browser work in node. Have you tried to convert a string to base64 using atob function? does not work.

Special Characters on symbols and functions names

What such a great idea! The way that we use the ? to mark functions that return boolean is awesome. Much better than adding an is upfront every funciton name like other languages do. Have you ever saw isNegative, isEmpty, isValid functions? is that that I’m talking about.

Besides that, as convention we use the ! to identify functions that have side effects and also make sense.

Clojure uses special characters with a bunch of different meanings. I really recommend that you visit this page to known more about special characters in Clojure.

Too much ‘def’

As I said has been 3 weeks and I keep seeing new “def” words. We start with the simple def, then the defn, and after two or three days of learning you’ll see: defmacro deftest defprotocol defrecord defonce defmethod deftype defstruct… and the list always gets bigger.

I think that by now I don’t have the knowledge to understand what’s going on with so much def. But the first impression is:

It looks like Clojure has more data structure than any other programming language and each “def” means a different kind of structure.

New Nomenclatures

I’ve never learned so many new words since I started programming..
Here we use symbols not variables, we have predicates, macros, protocols.

A Predicate is a thing that I’ve already learned in the university. But never heard in a programming language.
I feel a more complete programmer every time I understand what each new word means.

Weird things (by now)

• Why we don’t have a simple queue constructor? why do we have to use clojure.lang.PersistentQueue/EMPTY to generate an empty queue?
• Why the every? function has a ? and the some does not have? why some does not returns a boolean too?
• Why do pop and peek work in a way when dealing with lists and queues, and totally differently when dealing with vectors? Is it not easy to implement another function just for the vectors?
• Why I can use pprint in the clj but in the REPL of the IntelliJ I have to import it?

I hope that with more days of learning, I can answer these questions.

Conclusion

That’s it. Feel free to answer any of these questions. I’ll be happy to learn from you. In the next posts, I’ll be here to share more thoughts about the Clojure and would be nice to see you here again.

Thanks.

– Pedro.