michaelklishin / chash Goto Github PK

This code in clojurewerkz.chash.ring:

(def ^{:const true :tag long}
ring-top (dec (Math/pow 2 160)))

(defn ^long ring-increment
[^long n](quot ring-top n))

The first problem is that ^long before the name ring-increment does not make a function return a primitive long. It just puts useless metadata on the var and the function returns Object. That might be a bug in Clojure, I'm not sure.

The way to declare a primitive return type is to put the ^long type hint just before the vector of args. However, if you do that, then the compiler correctly throws an exception that ring-top is a double, not a long. Looking at the code, you try to put a long :tag on ring-top, but that cannot work, because the value is way too big to fit in a long.

I am not sure what the correct code should be, but probably something where ring-top is calculated using BigInteger methods would be better, then converting the result to bigint. Then perhaps move the return type hint for ring-increment, and coerce the bigint return value of quot to long using (long (quot ring-top n))