Attoparsec parser and maybe type
Hello, I have a type compose of 5 doubles data MyData = MyData Double Double Double Double Double now I have a file to parse whcih contain this | 1.0 2.0 3.0 4.0 5.0 | or | ---------no result ------------- | So I would like to create a parser which return a Maybe Mydata | 1.0 2.0 3.0 4.0 5.0 | -> Just MyData | ---------no result ------------- | -> Nothing How should I proceed I can write really trivially both parser but I do not know how to combine all this MyDataP1 = MyData <$> scientific <*> scientific NothingP = string "--------------- no result ----------------" Thanks for your help Frederic
Hello Frederic, On Wed, Aug 29, 2018 at 01:01:42PM +0000, PICCA Frederic-Emmanuel wrote:
Hello, I have a type compose of 5 doubles
data MyData = MyData Double Double Double Double Double
now I have a file to parse whcih contain this
| 1.0 2.0 3.0 4.0 5.0 | or | ---------no result ------------- |
<|> (or `choice`) is the way to do it [1]. Let us know if that worked! [1] http://hackage.haskell.org/package/attoparsec-0.13.2.2/docs/Data-Attoparsec-...
powderWilsonP :: Parser (Maybe PowderWilson) powderWilsonP = powderWilsonP1 <|> powderWilsonP2 where powderWilsonP1 :: Parser (Maybe PowderWilson) powderWilsonP1 = Just <$> ( PowderWilson <$> doubleP <*> doubleP <*> doubleP <*> doubleP <*> doubleP ) powderWilsonP2 :: Parser (Maybe PowderWilson) powderWilsonP2 = do skipSpace _ <- string "---------no results -----------" pure Nothing I will test it :)) thanks
participants (2)
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Francesco Ariis -
PICCA Frederic-Emmanuel