{

{-# LANGUAGE OverloadedStrings #-}

module Main (main) where

import System.Exit

import Data.ByteString.Lazy.Char8 (unpack)

}

%wrapper "posn-bytestring"

%encoding "UTF8"

$digit = 0-9			-- digits

$alpha = [a-zA-Z]		-- alphabetic characters

tokens :-

  $white+				;

  "--".*				;

  let					{ tok (\p _ -> Let p) }

  in					{ tok (\p _ -> In p) }

  $digit+                               { tok (\p s -> Int p (read (unpack s))) }

  [\=\+\-\*\/\(\)]                      { tok (\p s -> Sym p (head (unpack s))) }

  $alpha [$alpha $digit \_ \']*         { tok (\p s -> Var p (unpack s)) }

{

-- Each right-hand side has type :: AlexPosn -> String -> Token

-- Some action helpers:

tok f p s = f p s

-- The token type:

data Token =

	Let AlexPosn		|

	In  AlexPosn		|

	Sym AlexPosn Char	|

        Var AlexPosn String     |

	Int AlexPosn Int	|

	Err AlexPosn

	deriving (Eq,Show)

main = if test1 /= result1 then exitFailure

			   else exitWith ExitSuccess

test1 = alexScanTokens "  let in 012334\n=+*foo bar__'"

result1 = [Let (AlexPn 2 1 3),In (AlexPn 6 1 7),Int (AlexPn 9 1 10) 12334,Sym (AlexPn 16 2 1) '=',Sym (AlexPn 17 2 2) '+',Sym (AlexPn 18 2 3) '*',Var (AlexPn 19 2 4) "foo",Var (AlexPn 23 2 8) "bar__'"]

}