Ep 041: Why Do Clojurians Make Such a Big Deal About Immutability?

We cover several practical side effects of immutability and why we've become such big fans of data that doesn't let us down.

Each week, we answer a different question about Clojure and functional programming.

If you have a question you'd like us to discuss, tweet @clojuredesign, send an email to [email protected], or join the #clojuredesign-podcast channel on the Clojurians Slack.

This week, the question is: "Why do Clojurians make such a big deal about immutability?" We cover several practical side effects of immutability and why we've become such big fans of data that doesn't let us down.

Selected quotes:

"Well, we don't have Monads to talk about."
"What good is a program, if you can't change stuff!?"
"The memory cost of data structures is in proportion to the changes, not the users."
"I can hang on to a reference to the old state and a reference to the new state very cheaply."
"You can reduce comparison to referential equality."
"Once you can efficiently save every version of the state, going back to a previous version is no big deal."
"I love determinism. Determinism is trustable."
"I can trust immutable data. And if I can trust it, then it can occupy a smaller part of my brain."

Related episodes:

002: Tic-Tac-Toe, State in a Row
039: Why use Clojure over another functional language?