From 0765a9a1ea31b11075731f4f33b68b40b6f15154 Mon Sep 17 00:00:00 2001
From: Jed Barber <jjbarber@y7mail.com>
Date: Thu, 13 Mar 2014 23:40:39 +1100
Subject: GHC bug of some kind

---
 Unlambda/Interpreter.hs | 56 +++++++++++++++++++++++++++++++++++++++----------
 Unlambda/Parser.hs      | 10 ++++++++-
 2 files changed, 54 insertions(+), 12 deletions(-)

diff --git a/Unlambda/Interpreter.hs b/Unlambda/Interpreter.hs
index 1f0be35..b165887 100644
--- a/Unlambda/Interpreter.hs
+++ b/Unlambda/Interpreter.hs
@@ -4,30 +4,64 @@ module Unlambda.Interpreter (
 
 
 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 Unlambda.Parser
 
 
 
-data UnlambdaException = UnlambdaException { endTerm :: UnlambdaTerm }
-    deriving (Show, Typeable)
+type ULM a = ContT UnlambdaTerm (StateT UnlambdaState IO) a
 
-instance Control.Exception.Exception UnlambdaException
+data UnlambdaState = UnlambdaState { exit :: UnlambdaTerm -> ULM UnlambdaTerm
+                                   , curChar :: Maybe Char }
 
 
 
 
 unlambda :: UnlambdaTerm -> IO UnlambdaTerm
-unlambda term =
-    catches ((`runContT` return) $ eval term)
-            [ Handler ((\e -> return (endTerm e)) :: UnlambdaException -> IO UnlambdaTerm) ]
+unlambda term = (`getResult` return) (callCC $ \cont -> setExit cont >> setCurChar Nothing >> eval term)
 
 
 
-eval :: UnlambdaTerm -> ContT UnlambdaTerm IO UnlambdaTerm
+getResult :: (Monad m) => ULM a -> (a -> m a) -> m a
+getResult m f = f . runStateT . runContT $ m
+
+
+
+setExit :: (UnlambdaTerm -> ULM UnlambdaTerm) -> ULM ()
+setExit cont = do
+    state <- lift get
+    (lift put) (state { exit = cont })
+    return
+
+
+
+doExit :: UnlambdaTerm -> ULM UnlambdaTerm
+doExit term = do
+    state <- lift get
+    (exit state) term
+    return
+
+
+
+setCurChar :: Maybe Char -> ULM ()
+setCurChar ch = do
+    state <- lift get
+    (lift put) (state { curChar = ch })
+    return
+
+
+
+getCurChar :: ULM (Maybe Char)
+getCurChar = do
+    state <- lift get
+    return (curChar state)
+
+
+
+eval :: UnlambdaTerm -> ULM UnlambdaTerm
 eval term =
     case term of
         App f x -> do
@@ -37,7 +71,7 @@ eval term =
 
 
 
-apply :: UnlambdaTerm -> UnlambdaTerm -> ContT UnlambdaTerm IO UnlambdaTerm
+apply :: UnlambdaTerm -> UnlambdaTerm -> ULM UnlambdaTerm
 apply firstTerm secondTerm =
     case firstTerm of
         K -> eval secondTerm >>= return . Kpartial
@@ -74,7 +108,7 @@ apply firstTerm secondTerm =
             liftIO (putChar '\n')
             return t
 
-        E -> eval secondTerm >>= throw . UnlambdaException
+        E -> eval secondTerm >>= doExit
 
         Reed -> return I --do
             --t <- eval ch secondTerm
diff --git a/Unlambda/Parser.hs b/Unlambda/Parser.hs
index ec604cf..851fc01 100644
--- a/Unlambda/Parser.hs
+++ b/Unlambda/Parser.hs
@@ -9,11 +9,19 @@ module Unlambda.Parser (
 import Control.Applicative( some )
 import Control.Monad.Trans.Cont
 import Control.Monad.IO.Class
+import Control.Monad.Trans.State.Lazy
 import Data.Either
 import Text.ParserCombinators.Parsec
 
 
 
+type ULM a = ContT UnlambdaTerm (StateT UnlambdaState IO) a
+
+data UnlambdaState = UnlambdaState { exit :: UnlambdaTerm -> ULM UnlambdaTerm
+                                   , curChar :: Maybe Char }
+
+
+
 data UnlambdaTerm = S | K | I | V | R | D | C | E | Bar | Reed
                   | Dot Char
                   | Compare Char
@@ -22,7 +30,7 @@ data UnlambdaTerm = S | K | I | V | R | D | C | E | Bar | Reed
                   | Spartial UnlambdaTerm
                   | Sapp UnlambdaTerm UnlambdaTerm
                   | Promise UnlambdaTerm
-                  | Continuation (UnlambdaTerm -> ContT UnlambdaTerm IO UnlambdaTerm)
+                  | Continuation (UnlambdaTerm -> ULM UnlambdaTerm)
 
 
 instance Eq UnlambdaTerm where
-- 
cgit