{
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__'"]
}