Ytukyg

Clojurians:
Thank you for your attention on this question !

Here is case I'm thinking about, I want to define a immutable bank account record

(defrecord account [ name balance statements])

(def cash-account (->account :cash 0.0 ))

I have a function that will deposit money to that account ,and a new record of account shall return

(.deposit cash-account 100.0 )

;; returns a new cash-account with attributes 

;; name = :cash balance= 100, statment=[ [(2018,1,1),100 ] ]

With more and more deposit and withdraw happening , the field statement list will expanding with more and more transactions inside.

My question will be :
after 1000 transactions, there are 1000 elements in the statment field of latest account return.

When 1001th transaction happend:

will Clojure *copy* 1000 transactions in the statment field of old account record ,and append new transaction, save them into new account record ?

or Clojure just *append* the new transaction to the old account record and provide a new pointer to it , make it look like new account record like persistent map ?

Appreciate your help & many thanks

From https://clojure.org/reference/datatypes#_deftype_and_defrecord :

• defrecord provides a complete implementation of a persistent map


• deftype supports mutable fields, defrecord does not

so, in your case, it will not copy the transactions, instead it will use a persistent data structure so it will look like the transaction was appended.

Here are some more docs you should also check:

• https://www.braveclojure.com/functional-programming/


• https://clojure.org/guides/learn/sequential_colls


• https://purelyfunctional.tv/guide/clojure-collections/


• https://youtu.be/lJr6ot8jGQE