Best way to formulate type tests?

[dgr]

I was just looking at adding some corner case tests to plus.cljc and noticed that there are some tests for the resulting type of various addition operations. These tests are in a reader conditional for the :default case. For instance: (is (instance? clojure.lang.BigInt (+ 0 1N))). Is the expectation that all Clojure implementations default to having the same class structure as does Clojure JVM? Or would these tests be better written to use predicates? I don't have access to Clojure CLR to know what it returns for these tests, and I don't know how Jank is handling this, either.

For instance, would it be better to use

(defn big-int? [n]
  (and (integer? n)
       (not (int? n))))

(is (big-int? (+ 0 1N)))

instead of the explicit instance? test for clojure.lang.BitInt?

[jeaye]

I share the same concern with you, but I've been lenient so far, to get the Clojure JVM tests written first. To be clear, I don't expect any dialect to share the same class names. As far as I know, none of them do currently.

I think, rather than being so indirect about it, what we may want to do is to have a dedicated ns, maybe called clojure.core-test.portability or something, which exposes these functions and then each dialect can have different implementations of them. For example:

(defn big-int? [n]
  #?(:clj (instance? clojure.lang.BigInt n)
     :cljs (instance? js/BigInt n)
     :default (throw (ex-info "unimplemented: big-int?" {:n n})))))

If you'd like to get the ball rolling with this, please do!

[dgr]

OK, I'll try to think this through and perhaps create that portability namespace.

[dgr]

This is done. Closing.