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

This work is licensed under a Creative Commons Attribution 3.0 Unported License (including images & stylesheets). The source is available on Github.

## 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.