# Notation references

This project is an original MoonBit implementation. Public reference material defines notation behavior; no source code was copied from another Roman numeral library.

- Encyclopaedia Britannica, [Roman numeral](https://www.britannica.com/topic/Roman-numeral), for symbol values and conventional subtractive examples.
- Wolfram MathWorld, [Roman Numerals](https://mathworld.wolfram.com/RomanNumerals.html), for modern construction examples.
- Encyclopaedia Britannica, [Why Do Clocks and Watches Use IIII instead of IV?](https://www.britannica.com/story/why-do-clocks-and-watches-use-the-roman-numeral-iiii-instead-of-iv), for the clock-face convention.
- Unicode Consortium, [Number Forms chart](https://www.unicode.org/charts/PDF/U2150.pdf), for Roman compatibility character assignments.

## Implemented interpretation

Modern mode uses `I`, `V`, `X`, `L`, `C`, `D`, and `M` with subtractive pairs `IV`, `IX`, `XL`, `XC`, `CD`, and `CM`. Additive mode uses deterministic additive place forms. Clock mode is restricted to hours 1 through 12 and writes four as `IIII`. Extended mode uses one parenthesized canonical group multiplied by 1000, followed by an optional canonical remainder below 1000.

Roman notation varied by period and context. The project does not claim universal historical coverage. Each accepted grammar is selected explicitly and tested independently.