{

module Main (main) where

import System.Exit

}

%wrapper "basic"

$digit=0-9                      -- digits

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

tokens :-

  $white+				;

  "--".*				;

  let					{ \_ -> Let }

  in					{ \_ -> In }

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

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

  $alpha [$alpha $digit \_ \']*		{ \s -> Var s }

  -- a left-context pattern for testing

  ^ \#                                  ;

{

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

-- The token type:

data Token =

	Let 		|

	In  		|

	Sym Char	|

	Var String	|

	Int Int		|

	Err

	deriving (Eq,Show)

main = if test1 /= result1 then exitFailure

			   else exitWith ExitSuccess

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

result1 = identifierWithLotsOfQuotes''

identifierWithLotsOfQuotes'' :: [Token]

identifierWithLotsOfQuotes'' =

  [Let,In,Int 12334,Sym '=',Sym '+',Sym '*',Var "foo",Var "bar__'"]

}