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31 lines
746 B
Plaintext
31 lines
746 B
Plaintext
--State2 ability
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structural type Optional a = None | Some a
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structural ability State s where
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put : s -> {State s} ()
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get : {State s} s
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state : s -> Request (State s) a -> (s, a)
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state s = cases
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{ State.get -> k } -> handle k s with state s
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{ State.put snew -> k } -> handle k () with state snew
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{ a } -> (s, a)
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modify3 : (s -> s) -> ()
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modify3 f =
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s = State.get
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s2 = f s
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State.put s2
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---
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limitation here is that inferred ability vars can't refer to universal vars in
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the same type signature
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the inferred abilities are existentials, which are allocated up front, so
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they can't bind to the universals nor does that really make sense
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would need some nondeterminism or multiple phases in the typechecking process to
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do better
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