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47 lines
789 B
Text
47 lines
789 B
Text
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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 = 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 = 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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