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 discussion on the web visit > > 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