[Haskell-cafe] Why isn't ArrowChoice a parent of of ArrowApply?

[Petr Pudlák]

In Control.Arrow we have:

    |leftApp  ::ArrowApply  a => a b c -> a (Either  b d) (Either  c d)|

    Any instance of |ArrowApply| can be made into an instance of
    |ArrowChoice| by defining |left = leftApp|.

So why isn't |ArrowChoice| a parent of |ArrowApply|?

Best regards,
Petr

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