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93 lines
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93 lines
3.2 KiB
Markdown
# Roman Numerals
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Write a function to convert from normal numbers to Roman Numerals.
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The Romans were a clever bunch. They conquered most of Europe and ruled
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it for hundreds of years. They invented concrete and straight roads and
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even bikinis. One thing they never discovered though was the number
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zero. This made writing and dating extensive histories of their exploits
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slightly more challenging, but the system of numbers they came up with
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is still in use today. For example the BBC uses Roman numerals to date
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their programmes.
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The Romans wrote numbers using letters - I, V, X, L, C, D, M. (notice
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these letters have lots of straight lines and are hence easy to hack
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into stone tablets).
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```text
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1 => I
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10 => X
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7 => VII
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```
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There is no need to be able to convert numbers larger than about 3000.
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(The Romans themselves didn't tend to go any higher)
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Wikipedia says: Modern Roman numerals ... are written by expressing each
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digit separately starting with the left most digit and skipping any
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digit with a value of zero.
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To see this in practice, consider the example of 1990.
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In Roman numerals 1990 is MCMXC:
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1000=M
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900=CM
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90=XC
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2008 is written as MMVIII:
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2000=MM
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8=VIII
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See also: http://www.novaroma.org/via_romana/numbers.html
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## Exception messages
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Sometimes it is necessary to raise an exception. When you do this, you should include a meaningful error message to
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indicate what the source of the error is. This makes your code more readable and helps significantly with debugging. Not
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every exercise will require you to raise an exception, but for those that do, the tests will only pass if you include
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a message.
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To raise a message with an exception, just write it as an argument to the exception type. For example, instead of
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`raise Exception`, you should write:
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```python
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raise Exception("Meaningful message indicating the source of the error")
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```
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## Running the tests
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To run the tests, run the appropriate command below ([why they are different](https://github.com/pytest-dev/pytest/issues/1629#issue-161422224)):
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- Python 2.7: `py.test roman_numerals_test.py`
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- Python 3.4+: `pytest roman_numerals_test.py`
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Alternatively, you can tell Python to run the pytest module (allowing the same command to be used regardless of Python version):
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`python -m pytest roman_numerals_test.py`
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### Common `pytest` options
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- `-v` : enable verbose output
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- `-x` : stop running tests on first failure
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- `--ff` : run failures from previous test before running other test cases
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For other options, see `python -m pytest -h`
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## Submitting Exercises
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Note that, when trying to submit an exercise, make sure the solution is in the `$EXERCISM_WORKSPACE/python/roman-numerals` directory.
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You can find your Exercism workspace by running `exercism debug` and looking for the line that starts with `Workspace`.
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For more detailed information about running tests, code style and linting,
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please see [Running the Tests](http://exercism.io/tracks/python/tests).
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## Source
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The Roman Numeral Kata [http://codingdojo.org/cgi-bin/index.pl?KataRomanNumerals](http://codingdojo.org/cgi-bin/index.pl?KataRomanNumerals)
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## Submitting Incomplete Solutions
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It's possible to submit an incomplete solution so you can see how others have completed the exercise.
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