num

The Disco standard number theory library can be imported with

import num

It provides the following functions:

• isPrime : N -> Bool tests whether a given natural number is prime. It would be possible to implement this function in Disco, but this built-in version is much more efficient. For example it works on 15-digit numbers almost instantly.

• log(b,n) calculates the logarithm base b of n, rounded down to the nearest natural number.

• For convenience, lg is defined as the base-2 logarithm specifically. lg(n) + 1 is the number of bits needed to represent n in binary.

• factor takes a natural number and returns a bag of its prime factors. Like isPrime, this function could in theory be written in Disco itself, but the provided built-in version is extremely efficient.

• even and odd test whether a given integer is even or odd, respectively.