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23 lines
547 B
23 lines
547 B
module TryTry where |
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import Control.Applicative ((<|>)) |
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import Text.Trifecta |
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import Data.Ratio ((%)) |
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parseFraction :: Parser Rational |
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parseFraction = do |
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numerator <- decimal |
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char '/' |
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denominator <- decimal |
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case denominator of |
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0 -> fail "Denominator cannot be zero" |
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_ -> return (numerator % denominator) |
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type DecimalOrFraction = Either Integer Rational |
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parseDecimalOrFraction :: Parser DecimalOrFraction |
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parseDecimalOrFraction = (Right <$> (try parseFraction)) |
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<|> (Left <$> decimal) |
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