# API for clojure.math.numeric-tower - Math functions0.0.5 (in development)

by Mark Engelberg

Full namespace name: clojure.math.numeric-tower

## Overview

```Math functions that deal intelligently with the various
types in Clojure's numeric tower, as well as math functions
commonly found in Scheme implementations.

expt - (expt x y) is x to the yth power, returns an exact number
if the base is an exact number, and the power is an integer,
otherwise returns a double.
abs - (abs n) is the absolute value of n
gcd - (gcd m n) returns the greatest common divisor of m and n
lcm - (lcm m n) returns the least common multiple of m and n

When floor, ceil, and round are passed doubles, we just defer to
the corresponding functions in Java's Math library.  Java's
behavior is somewhat strange (floor and ceil return doubles rather
than integers, and round on large doubles yields spurious results)
but it seems best to match Java's semantics.  On exact numbers
(ratios and decimals), we can have cleaner semantics.

floor - (floor n) returns the greatest integer less than or equal to n.
If n is an exact number, floor returns an integer,
otherwise a double.
ceil - (ceil n) returns the least integer greater than or equal to n.
If n is an exact number, ceil returns an integer,
otherwise a double.
round - (round n) rounds to the nearest integer.
round always returns an integer.  round rounds up for values
exactly in between two integers.

sqrt - Implements the sqrt behavior I'm accustomed to from PLT Scheme,
specifically, if the input is an exact number, and is a square
of an exact number, the output will be exact.  The downside
is that for the common case (inexact square root), some extra
computation is done to look for an exact square root first.
So if you need blazingly fast square root performance, and you
know you're just going to need a double result, you're better
off calling java's Math/sqrt, or alternatively, you could just
convert your input to a double before calling this sqrt function.
If Clojure ever gets complex numbers, then this function will
need to be updated (so negative inputs yield complex outputs).
exact-integer-sqrt - Implements a math function from the R6RS Scheme
standard.  (exact-integer-sqrt k) where k is a non-negative integer,
returns [s r] where k = s^2+r and k < (s+1)^2.  In other words, it
returns the floor of the square root and the "remainder".```

## MathFunctions

Protocol

Known implementations: clojure.lang.BigInt, clojure.lang.Ratio, java.lang.Double, java.lang.Float, java.lang.Integer, java.lang.Long, java.math.BigDecimal, java.math.BigInteger

### ceil

function
```Usage: (ceil n)
```
```(ceil n) returns the least integer greater than or equal to n.
If n is an exact number, ceil returns an integer, otherwise a double.```

### floor

function
```Usage: (floor n)
```
```(floor n) returns the greatest integer less than or equal to n.
If n is an exact number, floor returns an integer, otherwise a double.```

### integer-length

function
```Usage: (integer-length n)
```
`Length of integer in binary`

### round

function
```Usage: (round n)
```
```(round n) rounds to the nearest integer.
round always returns an integer.  Rounds up for values exactly in between two integers.```

### sqrt

function
```Usage: (sqrt n)
```
`Square root, but returns exact number if possible.`

Source

## abs

function
```Usage: (abs n)
```
`(abs n) is the absolute value of n`

Source

## exact-integer-sqrt

function
```Usage: (exact-integer-sqrt n)
```
```(exact-integer-sqrt n) expects a non-negative integer n, and returns [s r] where n = s^2+r and n < (s+1)^2.  In other words, it returns the floor of the square root and the 'remainder'.
For example, (exact-integer-sqrt 15) is [3 6] because 15 = 3^2+6.```

Source

## expt

function
```Usage: (expt base pow)
```
```(expt base pow) is base to the pow power.
Returns an exact number if the base is an exact number and the power is an integer, otherwise returns a double.```

Source

## gcd

function
```Usage: (gcd a b)
```
`(gcd a b) returns the greatest common divisor of a and b`

Source

## lcm

function
```Usage: (lcm a b)
```
`(lcm a b) returns the least common multiple of a and b`

Source

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