This cookbook covers working with mathematics in Clojure, using built-in functions, contrib libraries, and parts of the JDK via interoperability.

Preliminaries

Some examples herein make use of the math.numeric-tower and math.combinatorics contrib libraries. It's assumed that either you have the following in your source code's ns macro:

(:require [clojure.math.numeric-tower :as math]
[clojure.math.combinatorics :as combo])

or else in the repl you've loaded them like so:

(require '[clojure.math.numeric-tower :as math])
(require '[clojure.math.combinatorics :as combo])

Recipes

Simple Math

(+ 3 4)    ;=> 7
(- 3 4)    ;=> -1
(* 3 4)    ;=> 12
(/ 3 4)    ;=> 3/4  (an exact ratio)
(/ 3.0 4)  ;=> 0.75

(inc 5)    ;=> 6
(dec 5)    ;=> 4

For doing integer division and getting remainders (modulus), see the docs for quot, rem, and mod.

For exponents, square roots, rounding, ceiling, floor, absolute value, and greatest/least common multiples, see the docs for math.numeric-tower.

Trigonometry

Use what the Java platform provides, for example:

Math/PI       ;=> 3.14159...
(Math/sin x)
(Math/cos x)
(Math/tan x)

There are many more functions available, which you can read about in the docs for java.lang.Math.

Combinatorics

For combinatoric functions (such as combinations and permutations), see the docs for math.combinatorics.