blob: 26050e6772e093ee248c2da176ba70ad2d00387f (
plain)
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
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
|
module Unlambda.Interpreter (
unlambda
) where
import System.IO.Error
import Control.Exception( Exception(..), Handler(..), throw, catches )
import Control.Monad.Trans.Class
import Control.Monad.Trans.Cont
import Control.Monad.Trans.State.Lazy
import Control.Monad.IO.Class
import Data.Typeable
import Data.Maybe
import Unlambda.Parser
type ULM a = ContT UnlambdaTerm (StateT (Maybe Char) IO) a
data UnlambdaException = UnlambdaException { exitValue :: UnlambdaTerm }
deriving (Show, Typeable)
instance Exception UnlambdaException
unlambda :: UnlambdaTerm -> IO UnlambdaTerm
unlambda term = catches ((`evalStateT` Nothing) . (`runContT` return) $ eval term)
[ Handler ((\e -> return . exitValue $ e) :: UnlambdaException -> IO UnlambdaTerm) ]
setCurChar :: Maybe Char -> ULM ()
setCurChar x = lift (put x)
getCurChar :: ULM (Maybe Char)
getCurChar = lift (get)
eval :: UnlambdaTerm -> ULM UnlambdaTerm
eval term =
case term of
App f x -> do
t <- eval f
apply t x
_ -> return term
apply :: UnlambdaTerm -> UnlambdaTerm -> ULM UnlambdaTerm
apply firstTerm secondTerm =
case firstTerm of
K -> eval secondTerm >>= return . Kpartial
Kpartial x -> eval secondTerm >> return x
S -> eval secondTerm >>= return . Spartial
Spartial x -> eval secondTerm >>= return . (Sapp x)
Sapp x y -> do
z <- eval secondTerm
eval (App (App x z) (App y z))
I -> eval secondTerm
V -> eval secondTerm >> return V
C -> callCC $ \cont -> eval (App secondTerm (Continuation cont))
Continuation cont -> eval secondTerm >>= cont
D -> return (Promise secondTerm)
Promise x -> eval secondTerm >>= eval . (App x)
Dot c -> do
t <- eval secondTerm
liftIO (putChar c)
return t
R -> do
t <- eval secondTerm
liftIO (putChar '\n')
return t
E -> eval secondTerm >>= throw . UnlambdaException
Reed -> do
t <- eval secondTerm
ch <- liftIO (catchIOError (getChar >>= return . Just) (\e -> return Nothing))
setCurChar ch
if (isNothing ch) then eval (App t V) else eval (App t I)
Bar -> do
t <- eval secondTerm
ch <- getCurChar
if (isNothing ch) then eval (App t V) else eval (App t I)
Compare c -> do
t <- eval secondTerm
ch <- getCurChar
if (ch /= Just c) then eval (App t V) else eval (App t I)
|