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ekmett / free

free monads
http://hackage.haskell.org/package/free
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Add weaving utils #222

Open alexfmpe opened 1 year ago

alexfmpe commented 1 year ago

I stumbled into weaveMax during some experiments with Free and one thing lead to another. If these are considered general/useful enough, I'd be up for implementing them for the other free encodings and adding comments.

Usage examples:

game :: Free IO (Maybe String)
game = Free $ getLine >>= \case
  "abracadabra" -> pure $ Pure $ Just "some reward"
  _ -> game <$ putStrLn "[Sorry, try again]"
> retract $ before (putStrLn "[Round start]") game
[Round start]
foo
[Sorry, try again]
[Round start]
bar
[Sorry, try again]
[Round start]
abracadabra
Just "some reward"

> retract $ after (putStrLn "[Round end]") game
foo
[Sorry, try again]
[Round end]
bar
[Sorry, try again]
[Round end]
abracadabra
[Round end]
Just "some reward"

> retract $ weaveMin (forever $ liftF $ putStrLn "[Round start]") game
[Round start]
foo
[Sorry, try again]
[Round start]
bar
[Sorry, try again]
[Round start]
abracadabra

> retract $ weaveMax game (for_ [0..1] $ \i -> liftF (putStrLn ("[Hint #" <> show i <> "]")))
foo
[Sorry, try again]
[Hint #0]
bar
[Sorry, try again]
[Hint #1]
baz
[Sorry, try again]
abracadabra
(Just "some reward",())