diff options
Diffstat (limited to 'src/Reducer.hs')
| -rw-r--r-- | src/Reducer.hs | 41 |
1 files changed, 22 insertions, 19 deletions
diff --git a/src/Reducer.hs b/src/Reducer.hs index 82de067..8823b3c 100644 --- a/src/Reducer.hs +++ b/src/Reducer.hs @@ -9,6 +9,7 @@ import Data.List ( elemIndex ) import Data.Map ( Map ) import qualified Data.Map as Map import Helper +import System.IO.Unsafe ( unsafePerformIO ) import System.Random ( randomIO ) type Store = Map Int Box @@ -20,30 +21,32 @@ data Rvar = Num Int | Hole data Redex = Rabs Int Redex | Rapp Redex Redex | Rvar Rvar | Rclosure Redex Store | Rcache Box Redex data Conf = Econf Redex Store Stack | Cconf Stack Redex | End -toRedex :: Expression -> IO Redex +-- TODO: unsafePerformIO is very unpure and ugly!! Unfortunately IO seems to +-- make this function and therefore the entire reduction strict :/ +toRedex :: Expression -> Redex toRedex = convertWorker [] where - convertWorker ns (Abstraction e) = do - v <- randomIO :: IO Int - t <- convertWorker (v : ns) e - pure $ Rabs v t - convertWorker ns (Application l r) = do - lhs <- convertWorker ns l - rhs <- convertWorker ns r - pure $ Rapp lhs rhs + convertWorker ns (Abstraction e) = + let v = unsafePerformIO randomIO :: Int + t = convertWorker (v : ns) e + in Rabs v t + convertWorker ns (Application l r) = + let lhs = convertWorker ns l + rhs = convertWorker ns r + in Rapp lhs rhs convertWorker ns (Bruijn i) = - pure $ Rvar $ Num (if i < 0 || i >= length ns then i else ns !! i) + Rvar $ Num (if i < 0 || i >= length ns then i else ns !! i) convertWorker _ _ = invalidProgramState -fromRedex :: Redex -> IO Expression +fromRedex :: Redex -> Expression fromRedex = convertWorker [] where - convertWorker es (Rabs n e) = Abstraction <$> convertWorker (n : es) e - convertWorker es (Rapp l r) = do - lhs <- convertWorker es l - rhs <- convertWorker es r - pure $ Application lhs rhs - convertWorker es (Rvar (Num n)) = pure $ Bruijn $ maybe n id (elemIndex n es) + convertWorker es (Rabs n e) = Abstraction $ convertWorker (n : es) e + convertWorker es (Rapp l r) = + let lhs = convertWorker es l + rhs = convertWorker es r + in Application lhs rhs + convertWorker es (Rvar (Num n)) = Bruijn $ maybe n id (elemIndex n es) convertWorker _ _ = invalidProgramState transition :: Conf -> IO Conf @@ -95,7 +98,7 @@ loadTerm t = Econf t Map.empty [] reduce :: Expression -> IO Expression reduce e = do - redex <- toRedex e + redex <- pure $ toRedex e forEachState (loadTerm redex) transition >>= \case - Cconf [] v -> fromRedex v + Cconf [] v -> pure $ fromRedex v _ -> invalidProgramState |