Building a function in Clojure that returns a 2D matrix with all initial values set to zero, for which I intended to use make-array.
(def m (make-array Integer/TYPE 3 3))
however what I get in return isn't the instance of the array (expected [[0 0 0] [0 0 0] [0 0 0]]) but got #object["[[I" 0x10014d2 "[[I@10014d2"].
I can properly access values in the m matrix via (get-in) and change them using (assoc-in), but ultimately I need to return the matrix, not the type of the object. Is there a way to do it?
PD. I'm new to stackoverflow and to Clojure.
It is really a matter of how your REPL is configured to display values. I get something similar in my REPL (launched with lein repl):
user=> (def m (make-array Integer/TYPE 3 3))
#'user/m
user=> m
#object["[[I" 0x4d632ca0 "[[I@4d632ca0"]
However, closer inspection shows that m is a Java array of Java integer arrays:
user=> (-> m class)
[[I
user=> (-> m class .getComponentType)
[I
user=> (-> m class .getComponentType .getComponentType)
int
Based on this answer we can configure the repl to display values differently:
user=> (clojure.main/repl :print pprint)
user=> m
[[0, 0, 0], [0, 0, 0], [0, 0, 0]]
But you may consider representing your matrix with vectors because they are immutable:
user=> (def m2 (reduce #(vec (repeat %2 %1)) 0 [3 3]))
#'user/m2
user=> m2
[[0 0 0] [0 0 0] [0 0 0]]