diff --git a/byg/byg.cabal b/byg/byg.cabal
index d7da384..7f8fa93 100644
--- a/byg/byg.cabal
+++ b/byg/byg.cabal
@@ -27,10 +27,12 @@ library
         DependencyGenerator
         Evaluation.Function
         Evaluation.FunctionIO
+        DependencyRunner
         SiteGenerator
     build-depends:
         base
       , mtl
+      , containers
       , bytestring
       , text
       , template-haskell
diff --git a/byg/src/DependencyRunner.hs b/byg/src/DependencyRunner.hs
new file mode 100644
index 0000000..6b759f3
--- /dev/null
+++ b/byg/src/DependencyRunner.hs
@@ -0,0 +1,98 @@
+module DependencyRunner
+  ( runDeps
+  ) where
+
+import Types (Value(..), Valuable(..))
+import Types.Dependency
+import Evaluation.Function
+import Evaluation.FunctionIO
+
+import Data.Map (Map)
+import qualified Data.Map as M
+import Control.Monad.State (MonadState, MonadIO, StateT, runState, put, get, modify, liftIO)
+
+newtype DepRunM a = DepRunM { unDepRunM :: StateT (Map Int Value) IO a }
+  deriving (Functor, Applicative, Monad, MonadIO, MonadState (Map Int Value))
+
+runDeps :: [Dependency] -> DepRunM ()
+runDeps = mapM_ runDep
+
+runDep :: Dependency -> DepRunM ()
+runDep (Dependency a action b) = do
+  input <- getTokenValue a
+  result <- runAction action input
+  putTokenValue b result
+
+getTokenValue :: UToken -> DepRunM Value
+getTokenValue = \case
+  UToken i -> do
+    m <- get
+    pure (m M.! i)
+  UTupleToken (a, b) -> do
+    va <- getTokenValue a
+    vb <- getTokenValue b
+    pure $ Tuple (va, vb)
+  UZipToken (a, b) -> do
+    va <- getTokenValue a
+    vb <- getTokenValue b
+    case (va, vb) of
+      (List as, List bs) ->
+        pure $ List $ zipWith (curry Tuple) as bs
+      _ ->
+        error "unexpected"
+  UNoToken ->
+    pure Empty
+
+putTokenValue :: UToken -> Value -> DepRunM ()
+putTokenValue t v = case t of
+  UToken i ->
+    modify $ M.insert i v
+  UNoToken ->
+    pure ()
+  _ ->
+    error "unexpected"
+
+runAction :: Action -> Value -> DepRunM Value
+runAction action input = case action of
+  Function f ->
+    pure $ evalFunction f input
+  FunctionIO f ->
+    liftIO $ evalFunctionIO f input
+  Inject v ->
+    pure v
+  FilterComp ->
+    case input of
+      Tuple (List vs, List mask) ->
+        pure $ List $ map fst $ filter (fromValue . snd) $ zip vs mask
+      _ ->
+        error "unexpected"
+  GetListElem ->
+    undefined
+  SetListElem ->
+    undefined
+  UntupleFst ->
+    case input of
+      Tuple (v, _) ->
+        pure v
+      _ ->
+        error "unexpected"
+  UntupleSnd ->
+    case input of
+      Tuple (_, v) ->
+        pure v
+      _ ->
+        error "unexpected"
+  UnzipFst ->
+    case input of
+      List vs ->
+        List <$> mapM (runAction UntupleFst) vs
+      _ ->
+        error "unexpected"
+  UnzipSnd ->
+    case input of
+      List vs ->
+        List <$> mapM (runAction UntupleSnd) vs
+      _ ->
+        error "unexpected"
+  MapComp subDeps ->
+    undefined
diff --git a/byg/src/Types/Value.hs b/byg/src/Types/Value.hs
index 8b71b43..40efe7a 100644
--- a/byg/src/Types/Value.hs
+++ b/byg/src/Types/Value.hs
@@ -20,12 +20,28 @@ data Value = String String
 
 class Valuable a where
   toValue :: a -> Value
+  fromValue :: Value -> a
 
 instance Valuable String where
   toValue = String
+  fromValue = \case
+    String a -> a
+    _ -> error "unexpected"
 
 instance Valuable Text where
   toValue = Text
+  fromValue = \case
+    Text a -> a
+    _ -> error "unexpected"
+
+instance Valuable Bool where
+  toValue = Bool
+  fromValue = \case
+    Bool a -> a
+    _ -> error "unexpected"
 
 instance Valuable ImageConversionSettings where
   toValue = ImageConversionSettings
+  fromValue = \case
+    ImageConversionSettings a -> a
+    _ -> error "unexpected"