Add evalState (to Control.Functor.Linear)
#404
Comments
|
I'm not sure that |
|
Maybe I can do without it, but I didn't see how because of the |
Replacing response type `Ur b` by simply `b` also checks and enables uses like ```haskell let (i, _) = HashMap.empty 100 (\ env -> runState (eval e) env) ``` (see issue tweag#404). Caveat: I am relying on the linea type checker (which might be in alpha state, dunno), so there might be reasons unknown to me why this generalization is invalid. Test suite passes, though.
|
I just tried to generalize the response type of So if this is an admissible generalization, the need for |
I ain't... |
Use case: stateful interpreter (`eval`) for C-like expressions `e`: ```haskell let Ur value = HashMap.empty capacity (\ env -> move (evalState (eval e) env)) ``` This pattern breaks the "jail" set by the type signature of `HashMap`-allocation: ```haskell empty :: Int -> (HashMap k v %1 -> Ur b) %1 -> Ur b ``` `HashMap` is not `Movable` but `Consumable`, so we can get rid of it before `move`ing the result to `Ur`.
Use case: stateful interpreter (`eval`) for C-like expressions `e`: ```haskell let Ur value = HashMap.empty capacity (\ env -> move (evalState (eval e) env)) ``` This pattern breaks the "jail" set by the type signature of `HashMap`-allocation: ```haskell empty :: Int -> (HashMap k v %1 -> Ur b) %1 -> Ur b ``` `HashMap` is not `Movable` but `Consumable`, so we can get rid of it before `move`ing the result to `Ur`.
Use case: stateful interpreter (`eval`) for C-like expressions `e`: ```haskell let Ur value = HashMap.empty capacity (\ env -> move (evalState (eval e) env)) ``` This pattern breaks the "jail" set by the type signature of `HashMap`-allocation: ```haskell empty :: Int -> (HashMap k v %1 -> Ur b) %1 -> Ur b ``` `HashMap` is not `Movable` but `Consumable`, so we can get rid of it before `move`ing the result to `Ur`.
|
@aspiwack : I am back to If you have other ideas how to write https://gist.github.com/andreasabel/f5c877491d32b653efba44cb283ba490#file-interpretermain-hs , please let me know. |
Use case: stateful interpreter (`eval`) for C-like expressions `e`: ```haskell let Ur value = HashMap.empty capacity (\ env -> move (evalState (eval e) env)) ``` This pattern breaks the "jail" set by the type signature of `HashMap`-allocation: ```haskell empty :: Int -> (HashMap k v %1 -> Ur b) %1 -> Ur b ``` `HashMap` is not `Movable` but `Consumable`, so we can get rid of it before `move`ing the result to `Ur`.
evalStateis a common use-case of the state monad.Probably there should also be
evalStateT.The text was updated successfully, but these errors were encountered: