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 > > > > > > > > > > > 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