[Haskell-beginners] Attoparsec parser question

24 May 2017

      Hello

I have this kind ot type

data PoniEntry a = PoniEntry { poniEntryHeader :: [Text]
                             , poniEntryDetector :: (Maybe (Detector a)) -- ^ Detector Name
                             , poniEntryPixelSize1 :: (Length Double) -- ^ pixels size 1
                             , poniEntryPixelSize2 :: (Length Double) -- ^ pixels size 1
                             , poniEntryDistance :: (Length Double) -- ^ pixels size 2
                             , poniEntryPoni1 :: (Length Double) -- ^ poni1
                             , poniEntryPoni2 :: (Length Double) -- ^ poni2
                             , poniEntryRot1 :: (Angle Double) -- ^ rot1
                             , poniEntryRot2 :: (Angle Double) -- ^ rot2
                             , poniEntryRot3 :: (Angle Double) -- ^ rot3
                             , poniEntrySpline :: (Maybe Text) -- ^ spline file
                             , poniEntryWavelength :: WaveLength -- ^ wavelength
                             }
                 deriving (Show)

type Poni a = [PoniEntry a]

And I try to create a Parser for the Poni type

lengthP :: Text -> Parser (Length Double)
lengthP key = do
  value <-doubleP key
  pure $ value *~ meter

detectorP ∷ ToPyFAI a ⇒ a → Parser a
detectorP a = do
  _ ← "Detector: " *> string (toPyFAI a) <* endOfLine
  pure a

poniEntryP ∷ Detector a ⇒ a → Parser (PoniEntry a)
poniEntryP a = PoniEntry
        <$> headerP
        <*> optional (detectorP a)
        <*> lengthP "PixelSize1: "
        <*> lengthP "PixelSize2: "
        <*> lengthP "Distance: "
        <*> lengthP "Poni1: "
        <*> lengthP "Poni2: "
        <*> angleP "Rot1: "
        <*> angleP "Rot2: "
        <*> angleP "Rot3: "
        <*> optional ("SplineFile: " *> takeTill isEndOfLine <* endOfLine)
        <*> lengthP "Wavelength: "
        <?> "poniEntryP"

poniP :: Detector a ⇒ a → Parser (Poni a)
poniP a = some (poniEntryP a)

But when I compile this I get this error message.

src/Hkl/PyFAI/Poni.hs:(118,16)-(131,24):
    Couldn't match type `attoparsec-0.10.4.0:Data.Attoparsec.Internal.Types.Parser
                           Text (PoniEntry a)'
                  with `a -> Parser (PoniEntry a)'
    Expected type: a -> Parser (PoniEntry a)
      Actual type: Parser (PoniEntry a)
    In the expression:
      PoniEntry <$> headerP <*> optional (detectorP a)
      <*> lengthP "PixelSize1: "
      <*> lengthP "PixelSize2: "
      <*> lengthP "Distance: "
      <*> lengthP "Poni1: "
      <*> lengthP "Poni2: "
      <*> angleP "Rot1: "
      <*> angleP "Rot2: "
      <*> angleP "Rot3: "
      <*> optional ("SplineFile: " *> takeTill isEndOfLine <* endOfLine)
      <*> lengthP "Wavelength: "
      <?> "poniEntryP"
    In an equation for `poniEntryP':
        poniEntryP a
          = PoniEntry <$> headerP <*> optional (detectorP a)
            <*> lengthP "PixelSize1: "
            <*> lengthP "PixelSize2: "
            <*> lengthP "Distance: "
            <*> lengthP "Poni1: "
            <*> lengthP "Poni2: "
            <*> angleP "Rot1: "
            <*> angleP "Rot2: "
            <*> angleP "Rot3: "
            <*> optional ("SplineFile: " *> takeTill isEndOfLine <* endOfLine)
            <*> lengthP "Wavelength: "
             "poniEntryP"

src/Hkl/PyFAI/Poni.hs:134:11-29:
    Couldn't match type `[Parser (PoniEntry a)]' with `Parser (Poni a)'
    Expected type: a -> Parser (Poni a)
      Actual type: a -> [Parser (PoniEntry a)]
    In the return type of a call of `some'
    In the expression: some (poniEntryP a)
    In an equation for `poniP': poniP a = some (poniEntryP a)

I must say, that I do not understand what is wrong with my code.

The lengthP code is ok, so why the detectorP is wrong ?

thanks for your help

Frederic

[Haskell-beginners] Attoparsec parser question

PICCA Frederic-Emmanuel