# Prime Factors in Haskell

#### Compute the prime factors of a given natural number.

1 | ```
exercism fetch haskell prime-factors
``` |

# Prime Factors

Compute the prime factors of a given natural number.

A prime number is only evenly divisible by itself and 1.

Note that 1 is not a prime number.

## Example

What are the prime factors of 60?

- Our first divisor is 2. 2 goes into 60, leaving 30.
- 2 goes into 30, leaving 15.
- 2 doesn't go cleanly into 15. So let's move on to our next divisor, 3.

- 3 goes cleanly into 15, leaving 5.
- 3 does not go cleanly into 5. The next possible factor is 4.
- 4 does not go cleanly into 5. The next possible factor is 5.

- 5 does go cleanly into 5.
- We're left only with 1, so now, we're done.

Our successful divisors in that computation represent the list of prime factors of 60: 2, 2, 3, and 5.

You can check this yourself:

- 2 * 2 * 3 * 5
- = 4 * 15
- = 60
- Success!

## Getting Started

For installation and learning resources, refer to the exercism help page.

## Running the tests

To run the test suite, execute the following command:

1 |
```
stack test
``` |

#### If you get an error message like this...

1 |
```
No .cabal file found in directory
``` |

You are probably running an old stack version and need to upgrade it.

#### Otherwise, if you get an error message like this...

1 2 |
No compiler found, expected minor version match with... Try running "stack setup" to install the correct GHC... |

Just do as it says and it will download and install the correct compiler version:

1 |
```
stack setup
``` |

## Running *GHCi*

If you want to play with your solution in GHCi, just run the command:

1 |
```
stack ghci
``` |

## Feedback, Issues, Pull Requests

The exercism/haskell repository on GitHub is the home for all of the Haskell exercises.

If you have feedback about an exercise, or want to help implementing a new one, head over there and create an issue. We'll do our best to help you!

## Source

The Prime Factors Kata by Uncle Bob http://butunclebob.com/ArticleS.UncleBob.ThePrimeFactorsKata

## Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.