RosettaCodeData/Task/Roman-numerals-Decode/Ring/roman-numerals-decode.ring

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symbols = "MDCLXVI"
weights = [1000,500,100,50,10,5,1]
see "MCMXCIX = " + romanDec("MCMXCIX") + nl
see "MDCLXVI =" + romanDec("MDCLXVI") + nl
see "XXV = " + romanDec("XXV") + nl
see "CMLIV = " + romanDec("CMLIV") + nl
see "MMXI = " + romanDec("MMXI") + nl
func romanDec roman
n = 0
lastval = 0
arabic = 0
for i = len(roman) to 1 step -1
n = substr(symbols,roman[i])
if n > 0 n = weights[n] ok
if n < lastval arabic = arabic - n
else arabic = arabic + n ok
lastval = n
next
return arabic