var tr = {
  "I": 1,
  "V": 5,
  "X": 10,
  "L": 50,
  "C": 100,
  "D": 500,
  "M": 1000
}

function solution (roman_string) {
  // Check if input is a string
  if (typeof roman_string !== 'string') {
    throw new TypeError('Input must be a string');
  }

  // Check if string is empty
  if (roman_string.length === 0) {
    throw new Error('String cannot be empty');
  }

  // Check if string contains only valid Roman numerals
  if (!/^M*(CM|CD|D?C{0,3})(XC|XL|L?X{0,3})(IX|IV|V?I{0,3})$/.test(roman_string)) {
    throw new Error('Invalid Roman numeral');
  }

  return roman_string.split('').map((letter, index, arr) => {
    const current_value = tr[letter];
    const next_value = tr[arr[index+1]];
    return next_value && current_value < next_value ? 
      (- current_value) : current_value;
  }).reduce((acc, item) => acc + item, 0);
}

fn math(s: &str) -> Result<i32, &'static str> {
    let math_str: String = s.chars().filter(|ch| !ch.is_whitespace()).collect();
    let (num1, num2) = math_str
        .split_once(|ch: char| matches!(ch, '+' | '-' | '*' | '/' | '='))
        .unwrap_or_else(|| panic!("missing operator, expected `+`, `-`, `*`, `/` or `=`"));
    let operator = &math_str[num1.len()..=num1.len()];
    let num1: i32 = num1.parse().unwrap_or_else(|_| panic!("invalid first operand"));
    let num2: i32 = num2.parse().unwrap_or_else(|_| panic!("invalid second operand"));

    match operator {
        "+" => Ok(num1 + num2),
        "-" => Ok(num1 - num2),
        "*" => Ok(num1 * num2),
        "/" => {
            if num2 != 0 {
                Ok(num1 / num2)
            } else {
                Err("Cannot divide by zero")
            }
        },
        "=" => Ok(i32::from(num1 == num2)),
        _ => Err("Invalid operator"),
    }
}