Function RomanToInt

conversion/romantoint.go:42–59

RomanToInt converts a roman numeral string to an integer. Roman numerals for numbers outside the range 1 to 3,999 will return an error. Nil or empty string return 0 with no error thrown.

(input string)

// outside the range 1 to 3,999 will return an error. Nil or empty string return 0
// with no error thrown.
func RomanToInt(input string) (int, error) {
	if input == "" {
		return 0, nil
	}
	var output int
	for _, n := range nums {
		for strings.HasPrefix(input, n.sym) {
			output += n.val
			input = input[len(n.sym):]
		}
	}
	// if we are still left with input string values then the
	// input was invalid and an error is returned.
	if len(input) > 0 {
		return 0, errors.New("invalid roman numeral")
	}
	return output, nil
}