I cannot turn this one into a problem with Typed Racket though. th must have type Thread and the -> Any of thread-receive requires a cast already, which covers our ‘soundness’ behind.
> On May 12, 2017, at 11:38 AM, Robby Findler <[email protected]> > wrote: > > Yeah, that's a real one. :) > > Robby > > On Fri, May 12, 2017 at 10:30 AM, Scott Moore <[email protected]> wrote: >> Reading a bit further in the docs, there is a bigger hole: >> >> (define (component-1 value channel) >> (thread-send channel value)) >> >> (define-values (component-2 channel) >> (let () >> (define main (current-thread)) >> (define th >> (thread (lambda () (thread-send main (thread-receive))))) >> (values (lambda () (thread-receive)) th))) >> >>> (component-1 (lambda () "hello world") channel) >>> ((component-2)) >> "hello world" >> >> On May 12, 2017, 11:05 AM -0400, Matthias Felleisen <[email protected]>, >> wrote: >> >> >> What your (cool little) program demonstrates is that *information* can flow >> from one thread to another, not *data*. You need to convince me that data >> flows and then we need to figure out how to protect/monitor this data. And >> at that point, you can possibly see lambdas flow too. >> >> >> >> On May 12, 2017, at 11:02 AM, Scott Moore <[email protected]> wrote: >> >> I think the interesting distinction is that threads, regexps, ports, etc, >> are communication channels, but not for higher-order values. >> >> On May 12, 2017, 10:58 AM -0400, Scott Moore <[email protected]>, >> wrote: >> >> (define (component-1 value) >> (define t >> (thread (lambda () >> (thread-suspend t) >> (for ([i (in-range value)]) >> (thread-suspend t))))) >> t) >> >> (define (component-2 thread) >> (thread-resume thread) >> (let* ([suspend-evt (thread-suspend-evt thread)] >> [dead-evt (thread-dead-evt thread)] >> [result (sync suspend-evt dead-evt)]) >> (if (eq? result dead-evt) >> 0 >> (add1 (component-2 thread))))) >> >> (define t (component-1 2)) >> (component-2 t) >> >> 2 >> >> (define t (component-1 5)) >> (component-2 t) >> >> 5 >> >> On May 12, 2017, 10:46 AM -0400, Robby Findler >> <[email protected]>, wrote: >> >> I would say that the event value is the channel of communication. But, >> if this expression: >> >> (sync (thread (lambda () 3))) >> >> returned 3, then I'd say that thread itself is a channel of >> communication. But threads give themselves back to sync, not the >> values that their thunks return. >> >> Robby >> >> On Fri, May 12, 2017 at 9:41 AM, Matthias Felleisen >> <[email protected]> wrote: >> >> >> I tend to agree though there is some information flowing from a thread to >> its context (thread CML events). I have to think whether this is a channel >> of communication. >> >> >> >> >> On May 12, 2017, at 8:57 AM, Robby Findler <[email protected]> >> wrote: >> >> This perspective suggests a gap in the design in some sense, I would >> say. The PL construct cannot, on its own, guarantee that the values >> from #:authentic structs end up behaving like those kinds of values. >> >> (also: threads and regexps don't seem problematic from the contract >> perspective, but ports do, since they are a communication channel and >> the others aren't.) >> >> Robby >> >> >> On Fri, May 12, 2017 at 7:52 AM, Matthew Flatt <[email protected]> wrote: >> >> I think a better analogy is to values like #<thread>, #<input-port>, or >> #<regexp>. Although those kinds of values are implemented with structs, >> the accessor and mutator functions are not exported (and, as Scott >> says, there's no way to get the accessors and mutations by reflection), >> so there's no way to impersonate the values. In general, it's up to the >> implementation of a new kind of value to supply impersonator/chaperone >> support for those values, and implementations usually don't. >> >> At Thu, 11 May 2017 19:00:43 -0400, Matthias Felleisen wrote: >> >> >> Oh right. >> >> >> On May 11, 2017, at 6:54 PM, Robby Findler <[email protected] >> >> wrote: >> >> >> They would be the same. We currently cannot chaperone or impersonate cons >> >> cells. We copy them. >> >> >> Robby >> >> On Thu, May 11, 2017 at 5:51 PM Matthias Felleisen <[email protected] >> >> wrote: >> >> >> Yes except that you can contract cons cells. So why couldn’t you contract >> >> authentic structs then? >> >> >> >> >> On May 11, 2017, at 6:41 PM, Robby Findler <[email protected] >> >> wrote: >> >> >> Indeed: if we did that, then these structs would be much like cons >> cells currently are. >> >> Robby >> >> >> On Thu, May 11, 2017 at 5:39 PM, Robby Findler >> <[email protected]> wrote: >> >> What if #:authentic (or whatever) were only allowed on immutable >> objects and we allowed them to be copied? Then contracts could protect >> them. >> >> Robby >> >> >> On Thu, May 11, 2017 at 5:38 PM, Matthias Felleisen >> <[email protected]> wrote: >> >> >> @ Christos >> >> #:authentic explicitly introduces a channel of communication that it is >> >> not protectable by contracts. This makes Racket’s contract system explicitly >> incomplete. It might have been incomplete in the past for other reasons. >> >> >> If the name isn’t fixed, #:no-proxy-allowed would be my preference. >> >> — Matthias >> >> >> >> >> >> On May 11, 2017, at 12:48 PM, Scott Moore <[email protected] >> >> wrote: >> >> >> I agree that generally don't want performance declarations that >> interfere with reasonable interposition. The good uses of `#:authentic` >> would be in places where the struct representation of a value is not >> exposed or where the values themselves are not exposed (so any >> interposition means being on the "inside" where you can change the >> code, anyway). >> >> >> Yes, I agree with this. I think as far as how this changes Racket’s >> >> data abstraction model, the key is “where the values themselves are not >> exposed.” >> >> #:authentic only has an interesting effect in the other case, where >> >> “outside” code gets its hands on a value of the struct type. Previously, I >> could write a program that used inspectors to impersonate this value >> regardless of the “inside” code’s intent. Now that would no longer be >> possible. >> >> >> I doubt there is much code that currently relies on being able to do >> >> this and so I would say go ahead. (Perhaps DrRacket or other debugging >> tools?) >> >> >> On the other hand, Spencer already asked if this would be something the >> >> optimization coach would recommend. I think it would be important for the >> documentation of #:authentic or the implementation of such a coach to stress >> the importance of the rules of thumb you just laid out. >> >> >> -- >> You received this message because you are subscribed to the Google >> >> Groups "Racket Developers" group. >> >> To unsubscribe from this group and stop receiving emails from it, send >> >> an email to [email protected]. >> >> To post to this group, send email to [email protected]. >> To view this discussion on the web visit >> >> https://groups.google.com/d/msgid/racket-dev/3c430798-e93a-4900-8215-198f77d9b9 >> 91%40Spark. >> >> For more options, visit https://groups.google.com/d/optout. >> >> >> -- >> You received this message because you are subscribed to the Google >> >> Groups "Racket Developers" group. >> >> To unsubscribe from this group and stop receiving emails from it, send >> >> an email to [email protected]. >> >> To post to this group, send email to [email protected]. >> To view this 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