Re: [Haskell-cafe] Transforming from on State-transformer to another

On Nov 20, 2019, at 1:08 PM, Jacques Carette wrote:

In the particular case of interest, I am interested in is actually b -> State a c -> (State (a,b) c), which is of course a special case of the above.

Use case: a Stateful computation where a local sub-computation needs more (local) state that will be, in-time, de-allocated.

Perhaps I misunderstood your use-case, but it seems that with a local sub-computation that needs extra state you can just: ... st <- get (c, (st', _)) <- runStateT local (st, extra) put st' ... where local :: StateT (a, b) m c. -- Viktor.