Add a Field1 instance for GHC.Tuple.Unit #878
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| @@ -110,6 +111,9 @@ class Field1 s t a b | s -> a, t -> b, s b -> t, t a -> s where | |||
| instance Field1 (Identity a) (Identity b) a b where | |||
| _1 f (Identity a) = Identity <$> f a | |||
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| instance Field1 (Unit a) (Unit b) a b where | |||
| _1 f (Unit a) = Unit <$> f a | |||
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Or should this be lazy???? I think all the tuple instances should be strict, but I know others disagree...
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I'd vote to keep it the way you've written it, as it's consistent with the other Field1 instances that are currently defined. If others feel strongly about changing this convention, then I think it would be best to leave that to a separate issue.
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Other Field1 insances are inconsistent. See Pair f g a and (a, b).
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Oops, I'm not sure what I was thinking when I wrote https://github.com/ekmett/lens/pull/878/files#r306307359, as the tuple instances are indeed implemented using irrefutable pattern matches. Hrm. I don't personally have a strong opinion on this, but for the sake of avoiding this PR from being bogged down by bikeshedding, it might be wise to stick to the current convention for now and raise a separate issue about how to reconcile the strictness of the instances for tuples and Product.
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We have _1' for when you want to reduce leaks
| @@ -110,6 +111,9 @@ class Field1 s t a b | s -> a, t -> b, s b -> t, t a -> s where | |||
| instance Field1 (Identity a) (Identity b) a b where | |||
| _1 f (Identity a) = Identity <$> f a | |||
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| instance Field1 (Unit a) (Unit b) a b where | |||
| _1 f (Unit a) = Unit <$> f a | |||
There was a problem hiding this comment.
I'd vote to keep it the way you've written it, as it's consistent with the other Field1 instances that are currently defined. If others feel strongly about changing this convention, then I think it would be best to leave that to a separate issue.
| @@ -63,6 +63,7 @@ import Data.Profunctor (dimap) | |||
| import Data.Proxy (Proxy (Proxy)) | |||
| import GHC.Generics ((:*:) (..), Generic (..), K1 (..), | |||
| M1 (..), U1 (..)) | |||
| import GHC.Tuple (Unit) | |||
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Based on the CI failures, I think this should be (Unit(..)).
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We could depend on |
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