Clojure's numeric tower is useful, but it can put a lot of steps between you and simple arithmetic. Unfortunately, while Clojure will warn you when reflection is required to invoke a function, it will not warn you when reflection is required to perform math. The only reliable way to discover whether you're calling
clojure.lang.Number.add(Object, Object) or
clojure.lang.Number.add(long, long) is to use a profiler or decompiler.
Or you can just bypass Clojure's math operators altogether.
primitive-math namespace, there are equivalents for every arithmetic operator and comparator that will give a reflection warning if it cannot compile down to a simple, predictable, unboxed mathematical operation.
primitive-math> (set! *warn-on-reflection* true) true primitive-math> (+ 3 3) 6 primitive-math> (defn adder [x] (+ 1 x)) ;; gives a reflection warning primitive-math> (defn adder [^long x] (+ 1 x)) ;; no reflection warning primitive-math> (+ 3.0 3) ;; gives a reflection warning AND throws an exception
To support operations on both
double types without any reflection, these operators are defined as macros. This means they cannot be used as higher-order functions:
primitive-math> (apply + [1 2 3]) ;; throws a 'cannot take value of macro' exception
In practice, it's usually preferable to import the namespace with a prefix, and use
p/== operators alongside the normal Clojure functions. However, if in a particular namespace you never need to use higher-order operators, you can call
(primitive-math/use-primitive-operators) to swap out the Clojure operators for their primitive equivalents. This can be reversed, using
an exhaustive list of operators
+ - * / ;; aliased as 'div' inc dec rem == not== zero? <= >= < > min max bool-and bool-or bool-not bool-xor true? false? bit-and bit-or bit-xor bit-not bit-shift-left ;; aliased as '<<' bit-shift-right ;; aliased as '>>' bit-unsigned-shift-right ;; aliased as '>>>' byte short int float long double byte->ubyte ubyte->byte short->ushort ushort->short int->uint uint->int long->ulong ulong->long reverse-short reverse-int reverse-long
Full documentation can be found here.
Copyright © 2013 Zachary Tellman
Distributed under the MIT License.