Remove HFunctor in preparation for improvements to Effect #295
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| build-depends: | ||
| base >= 4.9 && < 4.14 | ||
| , deepseq ^>= 1.4.3 |
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Meant to 🔥 this when we eliminated Resumable, but better now than after 1.0.
| @@ -3,3 +3,4 @@ | |||
| dist-newstyle | |||
| stack.yaml | |||
| cabal.project.local | |||
| .ghci | |||
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I’ve started using cabal exec ghci more and so I’m using this to set stuff up for that, but I don’t think we want to commit it since others will likely be using cabal repl and it might break or confuse things?
| @@ -179,7 +179,7 @@ instance | |||
| unReinterpretLogC k | |||
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| R other -> | |||
| ReinterpretLogC (alg (R (handleCoercible other))) | |||
| ReinterpretLogC (handleCoercible other) | |||
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This is where I’ve come down re: #235: this is all boilerplate, so let’s at least make it minimal, obvious, & consistent boilerplate.
| -- | Thread a 'Coercible' carrier through an 'Effect'. | ||
| -- | ||
| -- This is applicable whenever @m@ is 'Coercible' to @n@, e.g. simple @newtype@s. | ||
| -- | ||
| -- @since 1.0.0.0 | ||
| handleCoercible :: (Monad m, Effect eff, Member eff sig, Algebra sig n, Coercible m n) => eff m a -> n a | ||
| handleCoercible = handleIdentity coerce | ||
| {-# INLINE handleCoercible #-} |
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The new bit here is that handleCoercible calls (via handleIdentity) send, and thus no longer requires you to count Rs on the left.
| instance (Algebra sig m, Effect sig) => Algebra (Error e :+: sig) (ErrorC e m) where | ||
| alg = ErrorC . alg . handleCoercible | ||
| instance Algebra sig m => Algebra (Error e :+: sig) (ErrorC e m) where | ||
| -- NB: 'send' (& thus 'handleCoercible') can’t send sums, so we decompose the sum manually. | ||
| alg (L (L op)) = ErrorC (handleCoercible op) | ||
| alg (L (R op)) = ErrorC (handleCoercible op) | ||
| alg (R op) = ErrorC (handleCoercible op) |
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This is the one weird case: because handleCoercible uses send, and because send uses Member, and because Member can’t resolve sums of effects on the left, we have to decompose the sum here instead of doing just alg = ErrorC . handleCoercible.
I wouldn’t expect end users to have to do this very often, however, since it’s not very often you want to delegate all of the effects you handle to something else (how I wish we could simply GND-derive the instance!), or that (as in this case), you’re handling multiple effects combined in a sum, let alone both.
| => (forall x . eff m x -> m x) | ||
| -> (forall s . Reifies s (Handler eff m) => InterpretC s eff m a) | ||
| -> m a | ||
| runInterpret f m = reify (Handler (InterpretC . f . handleCoercible)) (go m) where | ||
| runInterpret f m = reify (Handler (InterpretC . fmap runIdentity . f . handle (Identity ()) (fmap Identity . coerce))) (go m) where |
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This is the other casualty of handleCoercible: we can’t use it here any more. I’m ok with that, again because this is something most users are unlikely to have to do themselves. In particular, users of runInterpret itself certainly don’t—runInterpretState bears no such scar.
| instance HFunctor (Catch e) where | ||
| hmap f (Catch m h k) = Catch (f m) (f . h) (f . k) | ||
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And now the good bit: 🔥
| @@ -52,7 +52,7 @@ import qualified Data.Semigroup as S | |||
| -- | |||
| -- @since 1.0.0.0 | |||
| (<|>) :: Has Choose sig m => m a -> m a -> m a | |||
| (<|>) a b = send (Choose (bool b a)) | |||
| a <|> b = send (Choose (bool b a)) | |||
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I really couldn’t tell you why I wrote it like that but when I noticed it I had to fix it.
Revert #295, reintroducing HFunctor.
This PR:
HFunctor.algintohandle…functions. (See also Allow Effect instances to constrain the context functor #296 & Rename handle to thread #300.)