2018-08-16 19:42:38 +03:00
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effect State s where
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get : {State s} s
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set : s -> {State s} ()
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effect Console where
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read : {Console} (Optional Text)
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write : Text -> {Console} ()
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fst x = case x of Pair.Pair a _ -> a
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2018-11-13 02:56:27 +03:00
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--TODO type is wrongly being inferred (or at least displayed) as `Pair a (Pair a b) ->{} a`
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2018-08-16 19:42:38 +03:00
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snd x = case x of Pair.Pair _ (Pair.Pair b _) -> b
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namespace Console where
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2018-08-23 21:56:50 +03:00
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state : s -> Effect (State s) a -> a
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state s c = case c of
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{State.get -> k} -> handle state s in k s
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{State.set s' -> k} -> handle state s' in k ()
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{a} -> a
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simulate : Effect Console d -> {State ([Text], [Text])} d
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2018-08-16 19:42:38 +03:00
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simulate c = case c of
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{Console.read -> k} ->
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io = State.get
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ins = fst io
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outs = snd io
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State.set (drop 1 ins, outs)
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2018-08-17 20:07:14 +03:00
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-- this really should typecheck but doesn't for some reason
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-- error is that `simulate` doesn't check against `Effect Console c -> r`,
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2018-09-24 21:38:03 +03:00
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-- but seems like that `r` should get instantiated as `{State (..)} c`.
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2018-08-16 19:42:38 +03:00
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handle simulate in k (at 0 ins)
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{Console.write t -> k} ->
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io = State.get
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ins = fst io
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outs = snd io
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2018-09-24 21:38:03 +03:00
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-- same deal here
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2018-08-16 19:42:38 +03:00
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handle simulate in k (State.set (ins, cons t outs))
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2018-08-23 21:56:50 +03:00
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{a} -> a
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2018-08-16 19:42:38 +03:00
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2018-09-24 21:38:03 +03:00
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(++) = (Text.++)
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2018-08-16 19:42:38 +03:00
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2019-02-12 22:10:33 +03:00
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x = handle Console.state ([],[]) in
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handle Console.simulate in
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use Console read write
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use Optional Some None
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write "What's your name?"
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case read of
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Some name -> write ("Hello" ++ name)
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None -> write "Fine, be that way."
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> x
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