Parser for readPrec

readprec.hs

-- Quick example of how to "properly" use readPrec with a "real" parser
import           Data.Char                    (isDigit, toUpper)
import qualified Text.ParserCombinators.ReadP as P
import qualified Text.Read                    as R

data WirePath = WirePath {d :: Char, a :: Int} deriving (Show)

instance R.Read WirePath where
    readPrec = R.readP_to_Prec $ const $ do
        c <- P.get
        s <- P.munch1 isDigit
        return $ WirePath {d = toUpper c, a = read s}