Remove mapM usage in monad

Was really a hack.

byg/src/ComputationM.hs

@@ -15,6 +15,7 @@ data TypedRun a b where
   F :: IsF f a b => f -> TypedRun a b
   FIO :: IsFIO f a b => f -> TypedRun a b
   TInject :: b -> TypedRun () b
+  GetListElem :: TypedRun () b
   InList :: ComputationM TokenNotTraversable b -> TypedRun [a] [b]
 
 instance Show (ComputationM t a) where
@@ -69,6 +70,9 @@ genDependency g = do
 inject :: Show a => a -> ComputationM ta a
 inject x = genDependency (Dependency NoToken (TInject x))
 
+getListElem :: Show a => ComputationM ta a
+getListElem = genDependency (Dependency NoToken GetListElem)
+
 run :: (Show a, Show b, IsF f a b) => f -> Token t a -> ComputationM TokenNotTraversable b
 run f input = genDependency (Dependency input (F f))
 

byg/src/Main.hs

@@ -1,13 +1,18 @@
 module Main where
 
+import Types
 import ComputationM
 
+testSub :: ComputationM TokenNotTraversable Image
+testSub = do
+  inp <- getListElem
+  openImage inp
+
 test :: ComputationM TokenNotTraversable ()
 test = do
   dir <- inject "retter"
   dirContents <- listDirectory dir
-  let dirContents' = makeTraversable dirContents
-  u <- mapM openImage dirContents'
+  u <- mapListTaken testSub dirContents
   pure $ NoToken
 
 main :: IO ()