Monad instance #22
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Monad instance #22
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Member
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It has been suggested before, but yeah rejected. It's not really the same as toMaybe (toNullable Nothing) = Nothing
toMaybe (toNullable (Just Nothing)) = Nothing |
Author
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That doesn't appear to be true.
:t toMaybe (toNullable (Just Nothing))
forall t4. Maybe (Maybe t4)
But I get the point.
toMaybe (notNull null) = Nothing
Now it is pretty obvious.
Sorry, and thanks for teaching me
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Contributor
Member
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Oops! But yeah, you got it - two layers of |
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Please excuse my ignorance, but I can't see a reason why Nullable,
effectively equal to Maybe, isn't at least a Functor or actually a Monad.
The instance definitions follow quite naturally. I can imagine
this is sort of an artificial barrier to foreign values. However,
to/from maybe conversion for the sake of using one of these instances
seems just wasteful for no particular good reason.
If I am overseeing something blatantly obvious here, it might
be good to document why this is not desireable/allowed.