text: # Roman Numerals
  
  Write a function to convert from normal numbers to Roman Numerals.
  
  The Romans were a clever bunch. They conquered most of Europe and ruled
  it for hundreds of years. They invented concrete and straight roads and
  even bikinis. One thing they never discovered though was the number
  zero. This made writing and dating extensive histories of their exploits
  slightly more challenging, but the system of numbers they came up with
  is still in use today. For example the BBC uses Roman numerals to date
  their programmes.
  
  The Romans wrote numbers using letters - I, V, X, L, C, D, M. (notice
  these letters have lots of straight lines and are hence easy to hack
  into stone tablets).
  
  ```text
   1  => I
  10  => X
   7  => VII
  ```
  
  There is no need to be able to convert numbers larger than about 3000.
  (The Romans themselves didn't tend to go any higher)
  
  Wikipedia says: Modern Roman numerals ... are written by expressing each
  digit separately starting with the left most digit and skipping any
  digit with a value of zero.
  
  To see this in practice, consider the example of 1990.
  
  In Roman numerals 1990 is MCMXC:
  
  1000=M
  900=CM
  90=XC
  
  2008 is written as MMVIII:
  
  2000=MM
  8=VIII
  
  See also: http://www.novaroma.org/via_romana/numbers.html
  
  ## 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 which 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 ignored 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 specific 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][modules] chapter if you
  haven't already, it will help you with organizing your files.
  
  ## Further improvements
  
  After you have solved the exercise, please consider using the additional utilities, described in the [installation guide](https://exercism.io/tracks/rust/installation), to further refine your final solution.
  
  To format your solution, inside the solution directory use
  
  ```bash
  cargo fmt
  ```
  
  To see, if your solution contains some common ineffective use cases, inside the solution directory use
  
  ```bash
  cargo clippy --all-targets
  ```
  
  ## Submitting the solution
  
  Generally you should submit all files in which you implemented your solution (`src/lib.rs` in most cases). If you are using any external crates, please consider submitting the `Cargo.toml` file. This will make the review process faster and clearer.
  
  ## 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]: https://exercism.io/tracks/rust/learning
  [modules]: https://doc.rust-lang.org/book/ch07-02-defining-modules-to-control-scope-and-privacy.html
  [cargo]: https://doc.rust-lang.org/book/ch14-00-more-about-cargo.html
  [rust-tests]: https://doc.rust-lang.org/book/ch11-02-running-tests.html
  
  ## Source
  
  The Roman Numeral Kata [http://codingdojo.org/cgi-bin/index.pl?KataRomanNumerals](http://codingdojo.org/cgi-bin/index.pl?KataRomanNumerals)
  
  ## Submitting Incomplete Solutions
  It's possible to submit an incomplete solution so you can see how others have completed the exercise.
  