alex

gistfile1.hs

{
module Main (main) where

import Control.Monad.IO.Class (liftIO)

}

%wrapper "monad"

$whitespace = [\ \b\t\n\f\v\r]
$digit      = 0-9
$alpha      = [a-zA-Z_]
$upper      = [A-Z]
$lower      = [a-z]
$char       = [A-Z a-z \!\#\$\%\&\*\+\.\/\<\=\>\?\@\\\^\|\-\~ 0-9 \:\"\']

$charesc = [abfnrtv\\\"\'\&]
@escape = \\ $charesc
@string = $char # [\"] | " " | @escape

tokens :-

$whitespace+ ;
$upper $alpha+ { mkL LTypeId }
$lower $alpha+ { mkL LId }
$digit+        { mkL LInt }
\" @string* \" { mkL LString }

{

data Lexeme = L AlexPosn LexemeClass (Maybe String) deriving (Show)

mkL :: LexemeClass -> AlexInput -> Int -> Alex Lexeme
mkL c (posn,_,_,s) n = return $ L posn c (Just $ take n s)

data LexemeClass
        = LTypeId
        | LId
        | LInt
        | LString
        | LEOF
    deriving (Show, Eq)

alexEOF = return (L undefined LEOF Nothing)

scanner str = runAlex str $ do
    let loop i = do l@(L _ c _) <- alexMonadScan
                    if c == LEOF
                         then return i
                         else do let i' = i++[l] in i' `seq` loop i'
    loop []

main :: IO ()
main = do
    s <- getContents
    print (scanner s)
--    let r = runAlex s alexMonadScan
--    print r
}