46 lines
1.4 KiB
Ceylon
46 lines
1.4 KiB
Ceylon
shared void run() {
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class Numeral(shared Character char, shared Integer int) {}
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value tiers = [
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[Numeral('I', 1), Numeral('V', 5), Numeral('X', 10)],
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[Numeral('X', 10), Numeral('L', 50), Numeral('C', 100)],
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[Numeral('C', 100), Numeral('D', 500), Numeral('M', 1k)]
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];
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String toRoman(Integer hindu, Integer tierIndex = 2) {
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assert (exists tier = tiers[tierIndex]);
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" Finds if it's a two character numeral like iv, ix, xl, xc, cd and cm."
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function findTwoCharacterNumeral() =>
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if (exists bigNum = tier.rest.find((numeral) => numeral.int - tier.first.int <= hindu < numeral.int))
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then [tier.first, bigNum]
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else null;
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if (hindu <= 0) {
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// if it's zero then we are done!
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return "";
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}
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else if (exists [smallNum, bigNum] = findTwoCharacterNumeral()) {
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value twoCharSymbol = "``smallNum.char````bigNum.char``";
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value twoCharValue = bigNum.int - smallNum.int;
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return "``twoCharSymbol````toRoman(hindu - twoCharValue, tierIndex)``";
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}
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else if (exists num = tier.reversed.find((Numeral elem) => hindu >= elem.int)) {
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return "``num.char````toRoman(hindu - num.int, tierIndex)``";
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}
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else {
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// nothing was found so move to the next smaller tier!
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return toRoman(hindu, tierIndex - 1);
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}
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}
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assert (toRoman(1) == "I");
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assert (toRoman(2) == "II");
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assert (toRoman(4) == "IV");
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assert (toRoman(1666) == "MDCLXVI");
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assert (toRoman(1990) == "MCMXC");
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assert (toRoman(2008) == "MMVIII");
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}
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