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|
module ParserM (
-- Parser Monad
ParserM(..), AlexInput, run_parser,
-- Parser state
St,
StartCode, start_code, set_start_code,
inc_brace_depth, dec_brace_depth,
-- Tokens
Token(..),
-- Actions
Action, andBegin, mkT, mkTv,
-- Positions
get_pos, show_pos,
-- Input
alexGetChar, alexGetByte, alexInputPrevChar, input, position,
-- Other
happyError
) where
import Control.Applicative
import Prelude hiding (fail)
import Control.Monad.Fail (MonadFail (..))
import Control.Monad (ap, liftM)
import Data.Word (Word8)
import Data.Char (ord)
-- Parser Monad
newtype ParserM a = ParserM (AlexInput -> St -> Either String (AlexInput, St, a))
instance Functor ParserM where
fmap = liftM
instance Applicative ParserM where
pure = return
(<*>) = ap
instance Monad ParserM where
ParserM m >>= k = ParserM $ \i s -> case m i s of
Right (i', s', x) ->
case k x of
ParserM y -> y i' s'
Left err ->
Left err
return a = ParserM $ \i s -> Right (i, s, a)
instance MonadFail ParserM where
fail err = ParserM $ \_ _ -> Left err
run_parser :: ParserM a -> (String -> Either String a)
run_parser (ParserM f)
= \s -> case f (AlexInput init_pos s) init_state of
Left es -> Left es
Right (_, _, x) -> Right x
-- Parser state
data St = St {
start_code :: !StartCode,
brace_depth :: !Int
}
deriving Show
type StartCode = Int
init_state :: St
init_state = St {
start_code = 0,
brace_depth = 0
}
-- Tokens
data Token = TEOF
| TArrow
| TDArrow
| TEquals
| TComma
| TOpenParen
| TCloseParen
| TOpenParenHash
| THashCloseParen
| TOpenBrace
| TCloseBrace
| TOpenBracket
| TCloseBracket
| TOpenAngle
| TCloseAngle
| TSection
| TPrimop
| TPseudoop
| TPrimtype
| TWith
| TDefaults
| TTrue
| TFalse
| TCompare
| TGenPrimOp
| TThatsAllFolks
| TLowerName String
| TUpperName String
| TString String
| TNoBraces String
| TInteger Int
| TFixity
| TInfixN
| TInfixL
| TInfixR
| TNothing
| TVector
| TSCALAR
| TVECTOR
| TVECTUPLE
deriving Show
-- Actions
type Action = String -> ParserM Token
set_start_code :: StartCode -> ParserM ()
set_start_code sc = ParserM $ \i st -> Right (i, st { start_code = sc }, ())
inc_brace_depth :: ParserM ()
inc_brace_depth = ParserM $ \i st ->
Right (i, st { brace_depth = brace_depth st + 1 }, ())
dec_brace_depth :: ParserM ()
dec_brace_depth = ParserM $ \i st ->
let bd = brace_depth st - 1
sc = if bd == 0 then 0 else 1
in Right (i, st { brace_depth = bd, start_code = sc }, ())
andBegin :: Action -> StartCode -> Action
(act `andBegin` sc) x = do set_start_code sc
act x
mkT :: Token -> Action
mkT t = mkTv (const t)
mkTv :: (String -> Token) -> Action
mkTv f str = ParserM (\i st -> Right (i, st, f str))
-- Positions
data Pos = Pos !Int{- Line -} !Int{- Column -}
get_pos :: ParserM Pos
get_pos = ParserM $ \i@(AlexInput p _) st -> Right (i, st, p)
alexMove :: Pos -> Char -> Pos
alexMove (Pos l _) '\n' = Pos (l+1) 1
alexMove (Pos l c) '\t' = Pos l ((c+8) `div` 8 * 8)
alexMove (Pos l c) _ = Pos l (c+1)
init_pos :: Pos
init_pos = Pos 1 1
show_pos :: Pos -> String
show_pos (Pos l c) = "line " ++ show l ++ ", column " ++ show c
-- Input
data AlexInput = AlexInput {position :: !Pos, input :: String}
-- alexGetByte is for Alex >= 3.0, alexGetChar for earlier
-- XXX no UTF-8; we should do this properly sometime
alexGetByte :: AlexInput -> Maybe (Word8,AlexInput)
alexGetByte (AlexInput p (x:xs)) = Just (fromIntegral (ord x),
AlexInput (alexMove p x) xs)
alexGetByte (AlexInput _ []) = Nothing
alexGetChar :: AlexInput -> Maybe (Char,AlexInput)
alexGetChar (AlexInput p (x:xs)) = Just (x, AlexInput (alexMove p x) xs)
alexGetChar (AlexInput _ []) = Nothing
alexInputPrevChar :: AlexInput -> Char
alexInputPrevChar _ = error "Lexer doesn't implement alexInputPrevChar"
happyError :: ParserM a
happyError = do p <- get_pos
fail $ "Parse error at " ++ show_pos p
|
