Polysemy State and Lens

polylens.hs

stateToStateViaLens :: Member (State bigSt) r
                    => Lens' bigSt smallSt
                    -> Sem (State smallSt ': r) a
                    -> Sem r a
stateToStateViaLens lens = interpret $ \case
  Put smallSt -> modify' (set lens smallSt)
  Get -> gets (view lens)

trylensplay2 :: IO ()
trylensplay2 = 
  print 
    $ run
    $ runState (5,10)
    $ stateToStateViaLens
    $ lensplay2

lensplay2 :: Member (State (Int, Int)) r => Sem r String
lensplay2 = do
  _1 *= 2
  _2 += 10
  pure "done!"