Displaying objects in REPL: Clojure equivalent of Java's toString?

[Dragan Djuric]

I have some custom types defined using deftype and I am trying to enable a human-friendly string representation of these types in repl. Something similar to #<Atom@123 "value">. How to do that in Clojure without redefining toString? It seems that Clojure use a different way to achieve this for atoms and refs, I just can't find what.

[Laurent PETIT]

I think you have to provide methods for multimethods print-dup and
print-method:

https://github.com/clojure/clojure/blob/c6756a8bab137128c8119add29a25b0a88509900/src/clj/clojure/core.clj#L3311

2013/8/1 Dragan Djuric <drag...@gmail.com>:

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[Armando Blancas]

Adding to that... have a look at the implemented methods in core_print.clj. The print-method will get called on print and println with your instance as the first argument. In this example prints a pair type; since elements can be anything it just calls print on each.

(deftype Pair [fst snd])

(defmethod print-method Pair [r, ^java.io.Writer w]

  (.write w "Pair(")

  (print (.fst r))

  (.write w ",")

  (print (.snd r))

  (.write w ")"))

[Dragan Djuric]

Thanks a lot, guys :)