CODEWITHSUNDEEP
clojuretype-hinting
Scott Klarenbach
Scott Klarenbach

Reputation: 38721

Clojure type hinting, Cannot resolve classname clojure.core$double

I have the following code, but when trying to type-hint the final normalize function, the compiler complains: Unable to resolve classname: clojure.core$double.

I don't see what's different about the normalize function that's not being done in sum-of-squares or vec-length.

Thanks.

(defn ^double sum-of-squares
  "Given a vector v, compute the sum of the squares of elements."
  [^doubles v]
  (r/fold + (r/map #(* % %) v)))

(defn ^double vec-length
  "Compute the length of vector v."
  [^doubles v]
  (Math/sqrt (sum-of-squares v)))

(defn ^doubles normalize
  "Compute the unit vector (normalize) v."
  [^doubles v]
  (let [l (vec-length v)]
    (into [] (r/map #(/ % l) v))))

Upvotes: 1

Views: 245

Answers (1)

squiddle
squiddle

Reputation: 1317

The type hint for the return values has to be placed before the arguments vector not before the name.

http://clojure.org/java_interop#Java%20Interop-Type%20Hints

Your first definition should look like this

(defn sum-of-squares
  "Given a vector v, compute the sum of the squares of elements."
  (^double [^doubles v]
    (r/fold + (r/map #(* % %) v))))

Upvotes: 2

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