func roman2arabic(digit) {
    digit.uc.trans([
        :M:  '1000+',
        :CM:  '900+',
        :D:   '500+',
        :CD:  '400+',
        :C:   '100+',
        :XC:   '90+',
        :L:    '50+',
        :XL:   '40+',
        :X:    '10+',
        :IX:    '9+',
        :V:     '5+',
        :IV:    '4+',
        :I:     '1+',
    ]).split('+').map{.to_i}.sum;
}
 
%w(MCMXC MMVIII MDCLXVI).each { |roman_num|
    say "#{roman_num}\t-> #{roman2arabic(roman_num)}";
}