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50 lines
980 B
Elm
50 lines
980 B
Elm
module RomanNumerals exposing (toRoman)
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import Dict
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import Maybe
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toRoman : Int -> String
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toRoman number =
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if number == 0 then
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""
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else
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let
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part =
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largestFactor number
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letter =
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numerals
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|> Dict.get part
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|> Maybe.withDefault ""
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in
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letter ++ (toRoman (number - part))
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largestFactor : Int -> Int
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largestFactor number =
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numerals
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|> Dict.keys
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|> List.filter (\p -> p <= number)
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|> List.reverse
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|> List.head
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|> Maybe.withDefault 0
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numerals : Dict.Dict Int String
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numerals =
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Dict.fromList
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[ ( 1000, "M" )
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, ( 900, "CM" )
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, ( 500, "D" )
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, ( 400, "CD" )
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, ( 100, "C" )
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, ( 90, "XC" )
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, ( 50, "L" )
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, ( 40, "XL" )
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, ( 10, "X" )
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, ( 9, "IX" )
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, ( 5, "V" )
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, ( 4, "IV" )
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, ( 1, "I" )
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]
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