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68 lines
1.8 KiB
Markdown
68 lines
1.8 KiB
Markdown
```unison
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structural ability Exception where raise : Failure -> x
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ex = unsafeRun! '(printLine "hello world")
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printLine : Text ->{IO, Exception} ()
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printLine t =
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putText stdOut t
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putText stdOut "\n"
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stdOut : Handle
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stdOut = stdHandle StdOut
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compose2 : (c ->{𝕖1} d) -> (a ->{𝕖2} b ->{𝕖3} c) -> a -> b ->{𝕖1,𝕖2,𝕖3} d
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compose2 f g x y = f (g x y)
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putBytes : Handle -> Bytes ->{IO, Exception} ()
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putBytes = compose2 toException putBytes.impl
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toException : Either Failure a ->{Exception} a
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toException = cases
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Left e -> raise e
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Right a -> a
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putText : Handle -> Text ->{IO, Exception} ()
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putText h t = putBytes h (toUtf8 t)
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Exception.unsafeRun! : '{Exception, g} a -> '{g} a
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Exception.unsafeRun! e _ =
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h : Request {Exception} a -> a
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h = cases
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{Exception.raise fail -> _ } ->
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bug fail
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{a} -> a
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handle !e with h
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```
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```ucm
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I found and typechecked these definitions in scratch.u. If you
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do an `add` or `update`, here's how your codebase would
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change:
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⍟ These new definitions are ok to `add`:
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structural ability Exception
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(also named builtin.Exception)
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Exception.unsafeRun! : '{g, Exception} a -> '{g} a
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compose2 : (c ->{𝕖1} d)
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-> (a ->{𝕖2} b ->{𝕖3} c)
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-> a
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-> b
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->{𝕖1, 𝕖2, 𝕖3} d
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ex : '{IO} ()
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printLine : Text ->{IO, Exception} ()
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putBytes : Handle
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-> Bytes
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->{IO, Exception} ()
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putText : Handle -> Text ->{IO, Exception} ()
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stdOut : Handle
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toException : Either Failure a ->{Exception} a
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```
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```ucm
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.> run ex
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```
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