Create GCoercible class, analogous to GEq
#46
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Ericson2314
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GCoercible class, analogous to GEq --- contains #45
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It could be a superclass of `GEq`, but this would be a breaking change and interferes with Safe Haskell, so we refrained from making it one.
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GCoercible class, analogous to GEq --- contains #45GCoercible class, analogous to GEq
| gcoercible (InR x) (InR y) = gcoercible x y | ||
| gcoercible _ _ = Nothing | ||
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| instance (GCoercible a, GCoercible b) => GCoercible (Product a b) where |
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This is weird (also in existing GEq instance. Either side would be enough, won't it?
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Huh? It is possible for one to fail and the other to succeed, is it not?
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For TestEquality yes only one is sufficient.
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Yes, I was thinking of TestEquality, and it doesn't seem to have instance for Product so all is fine.
(btw, that's another point not to have TestEquality as a super-class for GEq).
| return Coercion | ||
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| instance GCoercible IORef where | ||
| gcoercible x y = |
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I'll be more welcome to add this and STRef instance if the implementation for this function were in base, and I could use Safe (or at least Trustworthy) interface. (This package takes Safe Haskell seriously for time being).
Turns out there is for heterogenous equality for StableName (eqStableName), so figuring out coercion based on STRef equality kind of belongs to base as well.
As maintainer I'll be happy if burden of tracking GHC internals is in GHC-provided lib.
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I just had the same thought. The unsafe function should be where the implementation is, as those must be kept in sync?
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N.B. would be subsumed by #67. |
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