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{
module Main (main) where
import System.Exit
}
%wrapper "gscan"
$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 s)) }
[\=\+\-\*\/\(\)] { tok (\p s -> Sym p (head s)) }
$alpha [$alpha $digit \_ \']* { tok (\p s -> Var p s) }
{
-- Some action helpers:
tok f p _ str len cont (sc,state) = f p (take len str) : cont (sc,state)
-- 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 = alexGScan stop undefined " let in 012334\n=+*foo bar__'"
stop _ _ "" (_,_) = []
stop _ _ _ (_,_) = error "lexical error"
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__'"]
}
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