struct RomanNumeral {
    symbol: &'static str,
    value: u32
}

const NUMERALS: [RomanNumeral; 13] = [
    RomanNumeral {symbol: "M",  value: 1000},
    RomanNumeral {symbol: "CM", value: 900},
    RomanNumeral {symbol: "D",  value: 500},
    RomanNumeral {symbol: "CD", value: 400},
    RomanNumeral {symbol: "C",  value: 100},
    RomanNumeral {symbol: "XC", value: 90},
    RomanNumeral {symbol: "L",  value: 50},
    RomanNumeral {symbol: "XL", value: 40},
    RomanNumeral {symbol: "X",  value: 10},
    RomanNumeral {symbol: "IX", value: 9},
    RomanNumeral {symbol: "V",  value: 5},
    RomanNumeral {symbol: "IV", value: 4},
    RomanNumeral {symbol: "I",  value: 1}
];

fn to_hindu(roman: &str) -> u32 {
    match NUMERALS.iter().find(|num| roman.starts_with(num.symbol)) {
        Some(num) => num.value + to_hindu(&roman[num.symbol.len()..]),
        None => 0, // if string empty, add nothing
    }
}

fn main() {
    let roms = ["MMXIV", "MCMXCIX", "XXV", "MDCLXVI", "MMMDCCCLXXXVIII"];
    for &r in &roms {
        // 15 is minimum formatting width of the first argument, there for alignment
        println!("{:2$} = {}", r, to_hindu(r), 15);
    }
}