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module PGF.CId (CId(..),
mkCId, wildCId,
readCId, showCId,
-- utils
pCId, pIdent, ppCId) where
import Control.Monad
import qualified Data.ByteString.Char8 as BS
import Data.Char
import qualified Text.ParserCombinators.ReadP as RP
import qualified Text.PrettyPrint as PP
-- | An abstract data type that represents
-- identifiers for functions and categories in PGF.
newtype CId = CId BS.ByteString deriving (Eq,Ord)
wildCId :: CId
wildCId = CId (BS.singleton '_')
-- | Creates a new identifier from 'String'
mkCId :: String -> CId
mkCId s = CId (BS.pack s)
-- | Reads an identifier from 'String'. The function returns 'Nothing' if the string is not valid identifier.
readCId :: String -> Maybe CId
readCId s = case [x | (x,cs) <- RP.readP_to_S pCId s, all isSpace cs] of
[x] -> Just x
_ -> Nothing
-- | Renders the identifier as 'String'
showCId :: CId -> String
showCId (CId x) = BS.unpack x
instance Show CId where
showsPrec _ = showString . showCId
instance Read CId where
readsPrec _ = RP.readP_to_S pCId
pCId :: RP.ReadP CId
pCId = do s <- pIdent
if s == "_"
then RP.pfail
else return (mkCId s)
pIdent :: RP.ReadP String
pIdent = liftM2 (:) (RP.satisfy isIdentFirst) (RP.munch isIdentRest)
where
isIdentFirst c = c == '_' || isLetter c
isIdentRest c = c == '_' || c == '\'' || isAlphaNum c
ppCId :: CId -> PP.Doc
ppCId = PP.text . showCId
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