[racket-dev] Implementing contracts for async channels

I think they should probably all be exported from racket/async-channel.

Unless there is some reason to modify the internals of racket/contract
to support them?

Robby

On Thu, Jan 15, 2015 at 4:50 PM, Alexis King <lexi.lambda at gmail.com> wrote:
> Sorry, I wasn’t clear. The chaperone/impersonate-async-channel functions are exported from racket/async-channel. The async-channel contracts, however, are exported from racket/contract.
>
>> On Jan 15, 2015, at 14:41, Robby Findler <robby at eecs.northwestern.edu> wrote:
>>
>> Just a small nit: why export that function from racket/contract and
>> not an async-channel library?
>>
>> Robby
>>
>>
>> On Thu, Jan 15, 2015 at 3:33 PM, Alexis King <lexi.lambda at gmail.com> wrote:
>>> As an update, I’ve made a bit more progress on this. I’ve implemented an
>>> impersonate-async-channel function, and I’ve actually included this in the
>>> exports from racket/contract. I also realized the blame information is
>>> correct, it works fine. Most of the other issues remain, as well as a few
>>> new questions:
>>>
>>> There is no impersonate-evt function, so I’m not sure that my implementation
>>> will work. What should I do about this?
>>> I’d assume this needs to be documented/tested as well. Where should those
>>> things be located?
>>>
>>>
>>> On Jan 14, 2015, at 23:44, Alexis King <lexi.lambda at gmail.com> wrote:
>>>
>>> Currently, async channels do not have contracts to check their contents.
>>> This is a problem for Typed Racket, and it prevents typed code from
>>> interacting with code that produces async channels.
>>>
>>> I started looking into how to add contracts to the language, and it seems to
>>> use the chaperones/impersonator system, as I suspected. However, async
>>> channels obviously cannot be impersonated, so I needed to implement that as
>>> well.
>>>
>>> I modified the async-channel struct to use generics to allow it to be
>>> impersonated or chaperoned, which I have exposed by implementing
>>> chaperone-async-channel. I then tried implementing async-channel/c. The
>>> internals of the contract system are a little beyond me, but I got a working
>>> solution by following the example of the box contracts.
>>>
>>> My work thus far can be found here:
>>> https://github.com/lexi-lambda/racket/commit/84b9f3604891f3f2061fb28ed4800af8afa4751b
>>>
>>> First of all, is this a correct approach? Have I done anything wrong, or
>>> should I have done anything differently? I didn’t find much documentation on
>>> the internals of either of these systems, so I mostly went about things as I
>>> found them.
>>>
>>> Second, obviously, not everything is implemented here. Among the additional
>>> necessary changes are:
>>>
>>> I need to implement support for impersonators and impersonator contracts
>>> (right now I’ve only bothered to do chaperones).
>>> I need to implement async-channel/c-first-order and
>>> async-channel/c-stronger. I can probably figure out the latter, but I’m not
>>> even sure what the former is supposed to do.
>>> I need to implement a wrap-async-channel/c macro for the export. I’m not
>>> sure how this works, either. From looking at wrap-box/c, it seems to add
>>> some syntax properties, but I’m not sure what they do or how they work.
>>> Somehow, the blame information has to be correct. Is that what the wrap
>>> function does? Or do the async-channel functions need to be updated to
>>> assign blame?
>>>
>>>
>>> I’d really like to get this working, and I think I’m close, but I’m a little
>>> inexperienced. I’d appreciate any help, even if it’s just pointing me in the
>>> right direction.
>>>
>>> Thanks!
>>>
>>>
>>>
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>>>  http://lists.racket-lang.org/dev
>>>
>