func IntToRune(i int) rune {
	if i >= 0 && i <= 9 {
		return rune(i + '0')
	}
	return 'F'
}
IntToRune converts a digit 0 - 9 to the rune '0' - '9'. If the given int is outside
of this range 'F' is returned!
package utils
func RuneToInt(r rune) int {
	if r >= '0' && r <= '9' {
		return int(r - '0')
	}
	return -1
}