Platform-independent math functions in Clojure(script)

Question

How to access things like sin, cos or PI in a pure Clojure way?

For example, if I want to write a pure library, I mustn’t use anything like (.PI Math) (Java) or (.‑PI js/Math) (JS).

Answer 1

The easiest way is to use Cljx: https://github.com/lynaghk/cljx

With it you can write something like:

(* 5 #+clj (.PI Math) #+cljs (.‑PI js/Math))

and have this code compiled properly to Clojure and ClojureScript.

As far as I know there’s no better way to write one code to be runned as Clojure/ClojureScript.

There are some plans to include platform detection in Clojure itself but I think it’s not ready yet.

Answer 2

Cljx

Cljx has been deprecated for a few years. See the transition guide, which is also a good overview of the new solution:

.cljc

Code targeting multiple Clojure platforms is written in .cljc files using reader conditionals (introduced in Clojure 1.7).

The excellent kixi.stats implements platform-independent Clojure math using cljc, providing us not only a useful library but also a nice example of the approach. An excerpt:

(def PI
  #?(:clj Math/PI
     :cljs js/Math.PI))

(defn sin [x]
  #?(:clj  (Math/sin x)
     :cljs (js/Math.sin x)))

(def infinity
  #?(:clj Double/POSITIVE_INFINITY
     :cljs js/Infinity))

This code is from kixi.stats.math.

Answer 3

Sin example:

(.sin js/Math 3) 

PI example:

(aget js/Math "PI")

Displaying in console:

(.log js/console (aget js/Math "PI"))

Hope that helps.