# Rotational Cipher

Create an implementation of the rotational cipher, also sometimes called the Caesar cipher.

The Caesar cipher is a simple shift cipher that relies on
transposing all the letters in the alphabet using an integer key
between `0` and `26`. Using a key of `0` or `26` will always yield
the same output due to modular arithmetic. The letter is shifted
for as many values as the value of the key.

The general notation for rotational ciphers is `ROT + <key>`.
The most commonly used rotational cipher is `ROT13`.

A `ROT13` on the Latin alphabet would be as follows:

```text
Plain:  abcdefghijklmnopqrstuvwxyz
Cipher: nopqrstuvwxyzabcdefghijklm
```

It is stronger than the Atbash cipher because it has 27 possible keys, and 25 usable keys.

Ciphertext is written out in the same formatting as the input including spaces and punctuation.

## Examples

- ROT5  `omg` gives `trl`
- ROT0  `c` gives `c`
- ROT26 `Cool` gives `Cool`
- ROT13 `The quick brown fox jumps over the lazy dog.` gives `Gur dhvpx oebja sbk whzcf bire gur ynml qbt.`
- ROT13 `Gur dhvpx oebja sbk whzcf bire gur ynml qbt.` gives `The quick brown fox jumps over the lazy dog.`

## Rust Installation

Refer to the [exercism help page][help-page] for Rust installation and learning
resources.

## Writing the Code

Execute the tests with:

```bash
$ cargo test
```

All but the first test have been ignored. After you get the first test to
pass, open the tests source file wich is located in the `tests` directory
and remove the `#[ignore]` flag from the next test and get the tests to pass
again. Each separate test is a function with `#[test]` flag above it.
Continue, until you pass every test. 

If you wish to run all tests without editing the tests source file, use:

```bash
$ cargo test -- --ignored
```

To run a specific test, for example `some_test`, you can use:

```bash
$ cargo test some_test
```

If the specfic test is ignored use:

```bash
$ cargo test some_test -- --ignored
```

To learn more about Rust tests refer to the [online test documentation][rust-tests]

Make sure to read the [Modules](https://doc.rust-lang.org/book/second-edition/ch07-00-modules.html) chapter if you
haven't already, it will help you with organizing your files.

## Feedback, Issues, Pull Requests

The [exercism/rust](https://github.com/exercism/rust) repository on GitHub is the home for all of the Rust exercises. If you have feedback about an exercise, or want to help implement new exercises, head over there and create an issue. Members of the rust track team are happy to help!

If you want to know more about Exercism, take a look at the [contribution guide](https://github.com/exercism/docs/blob/master/contributing-to-language-tracks/README.md).

[help-page]: http://exercism.io/languages/rust
[modules]: https://doc.rust-lang.org/book/second-edition/ch07-00-modules.html
[cargo]: https://doc.rust-lang.org/book/second-edition/ch14-00-more-about-cargo.html
[rust-tests]: https://doc.rust-lang.org/book/second-edition/ch11-02-running-tests.html

## Source

Wikipedia [https://en.wikipedia.org/wiki/Caesar_cipher](https://en.wikipedia.org/wiki/Caesar_cipher)

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