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clojuretype-hinting

Implement methods which returns double : mismatch

I have trouble while trying to wrap up a clojure function into a Java interface. Here is the example :

(deftype ClojureDistanceMeasure [^clojure.lang.IFn f]
  DistanceMeasure
  (compute ^double [this ^doubles a ^doubles b] (double (f a b))))

(defn ->distance-measure
  ^DistanceMeasure
  [^clojure.lang.IFn f]
  (ClojureDistanceMeasure. f))

The compute method from DistanceMeasure (apache maths) is supposed to return. However, whatever type of type hinting I try (before args with ^, wrap into a hinted anonymous function), the progrom refuses to compile : mismatched return type, expected:double, had : java.lang.Object .

Is this a known issue ? Is there a way to override this (even with Java code) ?

I even tried silly code, did not work too 

(deftype ClojureDistanceMeasure [^clojure.lang.IFn f]
  DistanceMeasure
  (compute [this ^doubles a ^doubles b] (let [result (f a b)] (double (+ result 0.0)))))

This is strange because it works for other similar interfaces.

Thanks

Solution

  • This solves the problem :

    (deftype ClojureDistanceMeasure [^clojure.lang.IFn f]
  DistanceMeasure
  (compute ^double [this a b] (f ^doubles a ^doubles b)))

    Same without inner type hints : I must remove arguments hints and it works. I do not know if it is a Clojure missing part of issue tough.