37 lines
1.3 KiB
Markdown
37 lines
1.3 KiB
Markdown
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X-Date: 2024-10-15T22:54:31Z
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X-Note-Id: e2abd2ec-c537-4e15-a4a1-7eb374d48a06
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Subject: Reraising continuations
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X-Slug: reraising_continuations
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Reraising errors/continuations caused me some serious head-scratching, but now it's complete.
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You can reraise errors from the guard handler, and the continuation will be reattached to
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the place where it's been taken from as if nothing has happened, and the stack unwinding will
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proceed from the current guard handler and up.
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An example:
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```
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(fn main()
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(println "one")
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(println "two")
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(error "three")
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)
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(guard main
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(fn handler (err cont)
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(if (task? err)
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(reraise cont)
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(println "caught error" err)
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)))
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```
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Here, `main` calls 2 functions that cause side-effects and raise continuations. But the
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guard handler checks if this is a task and just reraises it, pretending that the handler
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never happened. It only will return from the handler upon receiving an error.
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The `reraise` building block will be very important when I start implementing a better-looking
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`try` macro. But for now it's already pretty convenient to be able to let the debug prints
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"fall through" the error handler.
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Check out [Valeri language](https://git.knazarov.com/knazarov/valeri) if you're interested.
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