In this challenge, we're going to write a function that converts an integer to its Roman numeral equivalent. IIf we give our method the Arabic number 476, our function will return the Roman Numeral CDLXXVI.
Has anyone ever seen a 5? Not a symbol we write on a piece of paper or print to a screen, but an actual, honest-to-goodness 5? Of course not. You've seen things that somehow embody five: five apples, five fingers, five weekdays on the calendar, a scrap of paper with 5 written on it, and so forth.
Think of all the ways to represent the integer 5. Symbols like 5, five, V, and IIIII are all ways to represent 5. If we asked a three-year-old, they might hold up the five fingers on their hand or pull out five pennies from their pocket. Computers encode numbers their own way, as a sequence of 0s and 1s called binary. The map is not the territory, as they say.
| Arabic Number | Roman Numeral |
|---|---|
| 1 | I |
| 5 | V |
| 10 | X |
| 50 | L |
| 100 | C |
| 500 | D |
| 1000 | M |
Table 1. Arabic number and their old Roman numeral equivalents.
In the early days of Roman numerals, the Romans built their numerals from the individual characters in Table 1 (e.g., I, V, X, etc.) written largest value to smallest from left to right. To determine the value of any numeral, they used straight addition. I is equivalent to 1. II is equivalent to 1 + 1, or 2. VIIII is equivalent to 5 + 1 + 1 + 1 + 1, or 9.
We are going to begin writing a function convertToOldRoman. When passed an integer between 1 and 3000, this function will return a string containing the proper old Roman Numeral. In other words, convertToOldRoman(4) should return the string 'IIII'. Don't worry about checking whether or not the number passed to the method is between 1 and 3000.
Be sure to test that your function works properly by writing tests.
Hint: It might be useful to use the integer division / and modulus % methods.
| Arabic Number | Roman Numeral |
|---|---|
| 4 | IV |
| 9 | IX |
| 14 | XIV |
| 44 | XLIV |
| 99 | XCIX |
| 400 | CD |
| 944 | CMXLIV |
Table 2. Modern Roman numeral examples.
Eventually, the Romans changed systems. Now, putting a smaller numeral before a larger one meant you had to subtract the smaller one. So, instead of 4 being represented by 1 + 1 + 1 + 1, it was now 5 - 1, or IV. 4 was not the only value affected (see Table 2 for more examples).
We're going to write a second method so that will return modern Roman Numerals. We'll most likely use some similar logic as in the first function.
convertToOldRoman(4)
=> "IIII"
convertToNewRoman(4)
=> "IV"Don't forget to write tests to ensure your function works properly.
An application you can run via your command line is wonderful, but let's add some functionality for a user to interact with the functions we've created. Someone may need to quickly know how an arabic number corresponds with a roman numeral!
We'll add a feature for a user to visit your page and enter a number (arabic number) and receive the corresponding roman numeral after pressing submit. To ensure this (somewhat tiny) application is user friendly, add some styling!
When you think you've completed this challenge, take a few minutes and see if there are places to refactor. Then, when you're confident you have the best solution, create a Pull Request back to this repository with your fully tested solution.