Data commit

Task/Roman-numerals-Decode/Ceylon/roman-numerals-decode.ceylon

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+shared void run() {
+	
+	value numerals = map {
+		'I' -> 1,
+		'V' -> 5,
+		'X' -> 10,
+		'L' -> 50,
+		'C' -> 100,
+		'D' -> 500,
+		'M' -> 1000
+	};
+	
+	function toHindu(String roman) {
+		variable value total = 0;
+		for(i->c in roman.indexed) {
+			assert(exists currentValue = numerals[c]);
+			/* Look at the next letter to see if we're looking
+			 at a IV or CM or whatever. If so subtract the
+			 current number from the total. */
+			if(exists next = roman[i + 1],
+				exists nextValue = numerals[next],
+				currentValue < nextValue) {
+				total -= currentValue;
+			} else {
+				total += currentValue;
+			}
+		}
+		return total;
+	}
+	
+	assert(toHindu("I") == 1);
+	assert(toHindu("II") == 2);
+	assert(toHindu("IV") == 4);
+	assert(toHindu("MDCLXVI") == 1666);
+	assert(toHindu("MCMXC") == 1990);
+	assert(toHindu("MMVIII") == 2008);
+}