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module Parser(parseProgram, parseExpression) where
import Control.Monad
import Control.Monad.Trans
import Data.Char
import Text.Parsec
import Text.Parsec.Pos
import AST
type Parser = ParsecT String () IO
parseProgram :: String -> IO (Either ParseError Program)
parseProgram = runParserT pProgram () ""
pProgram :: Parser Program
pProgram = between pWhiteComment eof (liftM Program (many pValue))
parseExpression :: String -> IO (Either ParseError Value)
parseExpression = runParserT pExpression () ""
pExpression :: Parser Value
pExpression = between pWhiteComment eof pValue
pValue :: Parser Value
pValue = pPPC <|> pVEllipsis <|> pVList <|> pVNum <|> pVString <|> pVName <|> pVQuoted <?> "value"
pVList :: Parser Value
pVList = flip label "list" $ do
symbol "("
exs <- many pValue
symbol ")"
return $ VList exs
pVNum :: Parser Value
pVNum = liftM (VNum . read) (many1 digit) <* pWhiteComment <?> "number"
pVString :: Parser Value
pVString = fmap VString pString
pVName :: Parser Value
pVName = flip label "name" $ do
first <- satisfy isFirstNameChar
rest <- many (satisfy isNameChar)
pWhiteComment
return $ VName $ first : rest
where
isNameChar c = ((c >= '*' && c <= 'z') || c `elem` "!$%&|~") && c /= ';'
isFirstNameChar c = isNameChar c && not (isDigit c)
pVQuoted :: Parser Value
pVQuoted = char '\'' >> liftM VQuoted pValue <?> "quoted value"
pVEllipsis :: Parser Value
pVEllipsis = symbol "..." >> return VEllipsis <?> "ellipsis"
pPPC :: Parser Value
pPPC = flip label "preprocessor command" $ do
symbol "#include"
fname <- pString
src <- liftIO $ readFile fname
stateBackup <- getParserState
void $ setParserState (State ("(do " ++ src ++ ")") (initialPos fname) ())
result <- pValue <* eof
void $ setParserState stateBackup
return result
symbol :: String -> Parser ()
symbol s = try (string s) >> pWhiteComment
pString :: Parser String
pString = flip label "string" $ do
void $ char '"'
s <- manyTill anyChar (symbol "\"")
return s
pWhiteComment :: Parser ()
pWhiteComment = do
pWhitespace
void $ many $ pComment >> pWhitespace
where
pWhitespace :: Parser ()
pWhitespace = void (many space) <?> "whitespace"
pComment :: Parser ()
pComment = flip label "comment" $ do
void $ char ';'
void (manyTill anyChar (void endOfLine <|> eof))
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