MonadVar.Lens

Documentation

(./) :: LensLike (Const s) v x s y -> LensLike f s t a b -> LensLike f v t a b infixr 9

Go down by _L into a data structure and apply _M to the result. This throws away the non-_L part of a structure, e.g. (a, (b, c)) & _2 ./ _2 %~ succ results in (b,d).

effectful :: Functor f => Lens s t a b -> Lens s (f t) a (f b)

Make a lens that runs with an effect out of a simple lens. E.g. ("a", "b") & effectful _2 .~ getLine asks for a string and replaces the second element of the tuple with it.

(.!) :: (Functor f, Functor g) => Lens v w s t -> LensLike g s (f t) a b -> LensLike g v (f w) a b infixr 9

Compose a simple lens and a lens that runs with some effect.

_VarM :: forall m n v a. MonadMutateM_ m n v => ASetter (v a) (n ()) a (m a)

A monadic setter for a variable. E.g. do v <- newIORef a v & _VarM %~ a -> succ a <$ putStr (show a) readIORef v >>= print prints a''b.

_Var :: forall m v a. MonadMutate_ m v => ASetter (v a) (m ()) a a

A setter for a variable. E.g. do v <- newIORef a v & _Var %~ succ readIORef v >>= print prints b.