Lazy Cofree constructor #92
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* Adds a `Lazy` instance. * Adds `buildCofree` which unfolds a label and subtree together.
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Should probably fix |
src/Control/Comonad/Cofree.purs
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| Cofree (e s) (defer \_ -> unfoldCofree e n <$> n s) | ||
| Cofree (defer \_ -> Tuple (e s) (unfoldCofree e n <$> n s)) | ||
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| buildCofree |
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It doesn't look like this is used, and it looks like a duplicate of unfoldCofree essentially. Is the idea just to save an extra allocation?
I would like to have only one, and deprecate the unfoldCofree if we decide to keep this.
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The problem with unfoldCofree is that the label and the functor are calculated independently, so they cannot share work. buildCofree supersedes unfoldCofree.
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Yeah, I'm happy to go with buildCofree, although it really is the natural unfold, of course, so I would prefer if we could use the name unfoldCofree. I suggest just adding a note that unfoldCofree will be replaced by buildCofree in a future release, please.
src/Control/Comonad/Cofree.purs
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| -- | Lazily creates a value of type `Cofree f a` from a label and a | ||
| -- | functor-full of "subtrees". | ||
| liftC :: forall f a. (Unit -> Tuple a (f (Cofree f a))) -> Cofree f a |
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This seems like a slightly unclear choice of name when we already have mkCofree. I would prefer to be more explicit and call it something like mkCofreeLazy but I'm open to other ideas.
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Yeah, I was just being consistent with liftF, which is an equally unclear name. Happy to change it to whatever.
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I agree we should change both. My open PR calls it liftFree actually, and moves it into a class.
src/Control/Comonad/Cofree.purs
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| liftC :: forall f a. (Unit -> Tuple a (f (Cofree f a))) -> Cofree f a | ||
| liftC = Cofree <<< defer | ||
| deferCofree :: forall f a. (Unit -> Tuple a (f (Cofree f a))) -> Cofree f a | ||
| deferCofree = Cofree <<< defer |
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I've called this deferCofree since it's just a specialized implementation of the Lazy instance.
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Great, thanks! |
Lazyinstance.buildCofreewhich unfolds a label and subtree together.