1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
|
{
module Main (main) where
}
%wrapper "gscan"
$digit = 0-9 -- digits
$alpha = [a-zA-Z] -- alphabetic characters
tokens :-
$white+ ;
"--".* ;
let { tok (\p s -> Let p) }
in { tok (\p s -> 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 c 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 = do
s <- getContents
print (alexGScan stop undefined s)
where
stop p c "" (sc,s) = []
stop p c _ (sc,s) = error "lexical error"
}
|