module Data.Fraction (
Fraction,
fromFactor,
fromPercentage,
toFactor,
toPercentage
) where
import Data.Semigroup as Semigroup
import Data.Monoid as Monoid
newtype Fraction = Fraction Double
instance Semigroup Fraction where
Fraction factor1 `append` Fraction factor2 = Fraction (factor1 * factor2)
instance Monoid Fraction where
mempty = Fraction 1
mappend = append
fromFactor :: Double -> Fraction
fromFactor factor | factor >= 0 && factor <= 1 = Fraction factor
| otherwise = error "fraction: factor out of bounds"
fromPercentage :: Double -> Fraction
fromPercentage perc | perc >= 0 && perc <= 100 = Fraction (perc / 100)
| otherwise = error "fraction: percentage out of bounds"
toFactor :: Fraction -> Double
toFactor (Fraction factor) = factor
toPercentage :: Fraction -> Double
toPercentage (Fraction factor) = factor * 100