Add IORef-based carrier for the Accum effect. #430
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No, I see what you mean by "slice." Mea culpa. |
robrix
approved these changes
Jul 12, 2022
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| Add w' -> liftIO (modifyIORef' ref (S.<> w')) | ||
| Look -> liftIO (readIORef ref) |
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Could factor out the liftIO, if you really cared to.
| instance (Algebra sig m, S.Semigroup w, MonadIO m) => Algebra (Accum w :+: sig) (AccumC w m) where | ||
| alg hdl sig ctx = case sig of | ||
| L accum -> do | ||
| ref <- AccumC (ask @(IORef w)) |
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Sometimes I prefer to do this sort of thing by constructing the ReaderC directly instead of asking with a type application, e.g.:
case sig of
L accum -> AccumC $ ReaderC $ \ ref -> do
…I'm not fussed either way.
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There exists no
IORef-based carrier for theWritereffect, as in an impure context there is no way to slice a section of the computation out (forlistenandpass). However, there is a very straightforward one for theAccumeffect. This defines such a carrier.