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 >>> https://groups.google.com/d/msgid/racket-dev/D688771A-C477-40D8-B209-D9506362C5 >>> CB%40ccs.neu.edu. >>>>>>> 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 >>> https://groups.google.com/d/msgid/racket-dev/1AFE0571-C48C-4B22-B445-D96B283C68 >>> 85%40ccs.neu.edu. >>>> 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 >>> https://groups.google.com/d/msgid/racket-dev/77B4F4BC-74B9-4838-AFC1-B65BCF8BE6 >>> 95%40ccs.neu.edu. >>> 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 >> https://groups.google.com/d/msgid/racket-dev/5915b006.5639620a.b51d4.83dcSMTPIN_ADDED_MISSING%40gmr-mx.google.com. >> 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 > https://groups.google.com/d/msgid/racket-dev/CAL3TdOPTT8-8CuJt86VE-_z%3DnZ%2B-Hxf92HyNW%3DvUtiVy9-5yAg%40mail.gmail.com. > 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. 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