Pure Programmer
Project: Roman Numerals
Ancient Rome used a system of numbers much different that the Hindu-Arabic numerals we use today. Today Roman Numerals are only used on movie copyrights, Olymipic games and the Superbowl. Write a program that converts the numbers from 1-2500 to [[Roman Numerals]] and prints them. Write a function that specifically does the Roman Numeral conversion. It should take an integer and return a string. The following table specifies the Roman Numerals and their corresponding integer values.
| Symbol | Value |
|---|---|
| I | 1 |
| IV | 4 |
| V | 5 |
| IX | 9 |
| X | 10 |
| XL | 40 |
| L | 50 |
| XC | 90 |
| C | 100 |
| CD | 400 |
| D | 500 |
| CM | 900 |
| M | 1000 |
With the right algorithm, generating Roman Numerals with the subtractice notation illustrated above is as simple as the additive form.
Output
$ rustc RomanNumerals.rs
error[E0308]: mismatched types
--> RomanNumerals.rs:14:34
|
14 | let mut currentPosition:isize = values.len() - 1;
| ----- ^^^^^^^^^^^^^^^^ expected `isize`, found `usize`
| |
| expected due to this
|
help: you can convert a `usize` to an `isize` and panic if the converted value doesn't fit
|
14 | let mut currentPosition:isize = (values.len() - 1).try_into().unwrap();
| + +++++++++++++++++++++
error[E0277]: the type `[isize]` cannot be indexed by `isize`
--> RomanNumerals.rs:16:22
|
16 | if value >= values[currentPosition] {
| ^^^^^^^^^^^^^^^ slice indices are of type `usize` or ranges of `usize`
|
= help: the trait `SliceIndex<[isize]>` is not implemented for `isize`
= help: the trait `SliceIndex<[T]>` is implemented for `usize`
= note: required for `Vec<isize>` to implement `Index<isize>`
error[E0277]: the type `[&'static str]` cannot be indexed by `isize`
--> RomanNumerals.rs:17:26
|
17 | result += romanSymbol[currentPosition];
| ^^^^^^^^^^^^^^^ slice indices are of type `usize` or ranges of `usize`
|
= help: the trait `SliceIndex<[&'static str]>` is not implemented for `isize`
= help: the trait `SliceIndex<[T]>` is implemented for `usize`
= note: required for `Vec<&'static str>` to implement `Index<isize>`
error[E0368]: binary assignment operation `+=` cannot be applied to type `&str`
--> RomanNumerals.rs:17:4
|
17 | result += romanSymbol[currentPosition];
| ------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
| |
| cannot use `+=` on type `&str`
error[E0277]: the type `[isize]` cannot be indexed by `isize`
--> RomanNumerals.rs:18:20
|
18 | value -= values[currentPosition];
| ^^^^^^^^^^^^^^^ slice indices are of type `usize` or ranges of `usize`
|
= help: the trait `SliceIndex<[isize]>` is not implemented for `isize`
= help: the trait `SliceIndex<[T]>` is implemented for `usize`
= note: required for `Vec<isize>` to implement `Index<isize>`
error[E0308]: mismatched types
--> RomanNumerals.rs:23:9
|
10 | fn convertToRomanNumerals(i:isize) -> String {
| ------ expected `String` because of return type
...
23 | return result;
| ^^^^^^- help: try using a conversion method: `.to_string()`
| |
| expected `String`, found `&str`
error: aborting due to 6 previous errors
Some errors have detailed explanations: E0277, E0308, E0368.
For more information about an error, try `rustc --explain E0277`.