The problem with Typed Racket would come from sending a higher order value to an untyped thread. I'm pretty sure you could get unsoundness there.
On Fri, May 12, 2017, 12:00 PM Matthias Felleisen <[email protected]> wrote: > > 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 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