14 lines
471 B
Haskell
14 lines
471 B
Haskell
digit x y z k =
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[[x],[x,x],[x,x,x],[x,y],[y],[y,x],[y,x,x],[y,x,x,x],[x,z]] !!
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(fromInteger k - 1)
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toRoman :: Integer -> String
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toRoman 0 = ""
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toRoman x | x < 0 = error "Negative roman numeral"
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toRoman x | x >= 1000 = 'M' : toRoman (x - 1000)
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toRoman x | x >= 100 = digit 'C' 'D' 'M' q ++ toRoman r where
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(q,r) = x `divMod` 100
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toRoman x | x >= 10 = digit 'X' 'L' 'C' q ++ toRoman r where
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(q,r) = x `divMod` 10
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toRoman x = digit 'I' 'V' 'X' x
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