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23 lines
731 B
Plaintext
23 lines
731 B
Plaintext
--handle inference
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structural ability State s where
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get : ∀ s . () -> {State s} s
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set : ∀ s . s -> {State s} ()
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state : ∀ a s . s -> Request (State s) a -> a
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state s = cases
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{a} -> a
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{State.get _ -> k} -> handle k s with state s
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{State.set s -> k} -> handle k () with state s
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-- modify : ∀ s . (s -> s) -> {State s} ()
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-- modify f = State.set (f (State.get()))
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ex : () -> {State Nat} Nat
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ex blah =
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State.get() Nat.+ 42
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-- note this currently succeeds, the handle block
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-- gets an inferred type of ∀ a . a, it appears that
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-- the existential `a` which gets instantiated for the
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-- state call never gets refined, most likely due to
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-- missing a subtype check in handle
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y : Text
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y = handle ex () with state 5
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()
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