Copyright | Copyright (C) 2021 Yoo Chung |
---|---|

License | GPL-3.0-or-later |

Maintainer | dev@chungyc.org |

Safe Haskell | Safe-Inferred |

Language | GHC2021 |

Part of Ninety-Nine Haskell Problems. Some solutions are in Solutions.P34.

# Documentation

totient :: Integral a => a -> a Source #

Calculate Euler's totient function \(\phi(m)\).

Euler's so-called totient function \(\phi(m)\) is defined as the number of positive integers \(r\), where \(1 \leq r \leq m\), that are coprime to \(m\).

For example, with \(m = 10\), \(\{r \,|\, 1 \leq r \leq m, \textrm{coprime to $m$}\} = \{ 1, 3, 7, 9 \}\); thus \(\phi(m) = 4\). Note the special case of \(\phi(1) = 1\).

### Examples

`>>>`

4`totient 10`