Protocol equivalent of Python's `repr`?

[Sam Raker]

I'm working my way through an intro to Clojure book, and I just got to the section on protocols. I might be missing something/committing a category error, but I'm wondering if there's a way to change the way a protocol is represented in the repl, akin to redefining `__repr__`/`__str__` in Python. The example protocol in the book involves a matrix (i.e., a vector of vectors). I can do this

(extend-protocol Matrix

    clojure.lang.IPersistentVector

    ...

    (pprint [vov] (clojure.pprint/pprint vov)))

which works fine when I call (pprint m) on a Matrix m:

(pprint m)

; [[0 0 0]

   [0 0 0]

   [0 0 0]]

What I'd like is to just have the same behavior "calling" the variable from the repl, i.e.

m

; [[0 0 0]

   [0 0 0]

   [0 0 0]]

Can/should this be done? Is this a job for macros? Am I just being lazy/un-Clojuric and just get over it and use (pprint m)?

[James Reeves]

The multimethods print-method and print-dup handle this.

- James

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[Jony Hudson]

You might also enjoy looking at Gorilla REPL [1], which has an easily extensible renderer [2] for just this sort of thing. Disclosure: I'm one of its authors!

Jony

[1] http://gorilla-repl.org

[2] http://vimeo.com/89532785

[Sam Raker]

James: I haven't gotten to multimethods yet--I'll definitely check that out!

Jony: I use Gorilla REPL for basically all my clojure stuff already! It's really great, thanks so much. I know you can add stuff to project.clj to pretty-print everything in the repl, I was just wondering about targeting specific protocols and types.

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