parsesamples.hs

{-# LANGUAGE OverloadedStrings, GeneralizedNewtypeDeriving #-}
module Text.Fractions where
import Control.Applicative
import Data.Ratio ((%))
import Text.Trifecta
import Test.Hspec

badFraction = "1/0"
alsoBad = "10"
shouldWork = "1/2"
shouldAlsoWork = "2/1"

newtype PitchClass = PitchClass Int deriving (Show, Num)

addPitchClasses'' x y =
  x + y

addPitchClasses :: PitchClass -> PitchClass -> PitchClass
addPitchClasses (PitchClass x) (PitchClass y) =
  PitchClass (x + y)

parsePitchClass :: Parser PitchClass
parsePitchClass =
  PitchClass . fromInteger <$> integer

parsePitchClass' :: Parser PitchClass
parsePitchClass' = do
  x <- integer
  return (PitchClass $ fromInteger x)


parseFraction :: Parser Rational
parseFraction = do
  numerator <- decimal
  char '/'
  denominator <- decimal
  case denominator of
    0 -> fail "Denominator cannot be zero"
    _ -> return (numerator % denominator)

parseFractionInParenthesis =
  parens parseFraction

maybeSuccess :: Result a -> Maybe a
maybeSuccess (Success a) = Just a
maybeSuccess _ = Nothing

main :: IO ()
main = hspec $ do
  describe "test" $
    it "can do this" $ do
      let r' = 1
      print r'
      r' `shouldBe` 1