[racket-dev] proposed clarification to "async-apply" docs

From: Jon Rafkind (rafkind at cs.utah.edu)
Date: Tue Nov 16 17:57:36 EST 2010

FWIW I agree with John and disagree with Jay.

On 11/16/2010 03:45 PM, Jay McCarthy wrote:
> The typesetting on async-apply clearly refers to the argument rather
> than to a well-known function. This is a convention of the docs that I
> don't think merits special attention here, although this case may
> indicate we should make a "how to read the documentation" section that
> points out these conventions.
> Jay
> On Tue, Nov 16, 2010 at 1:26 PM, John Clements
> <clements at brinckerhoff.org> wrote:
>> My quick reading of the documentation for the #:async-apply argument to the _fun form led to a misunderstanding; the docs seemed to be suggesting that some built-in 'async-apply' procedure was doing all of these magical things, whereas the point was to indicate that the *user* must provide an async-apply that behaves correctly.  I wound up going through and replacing 'async-apply' with 'the given async-apply procedure' in about five places. I think the text is clearer now; let me know if I shouldn't commit these changes. Otherwise, I'll commit them locally and push them sometime soon.
>> John
>> pcp062767pcs:~/plt/collects/scribblings/foreign clements$ git diff types.scrbl
>> diff --git a/collects/scribblings/foreign/types.scrbl b/collects/scribblings/foreign/types.scrbl
>> index 9d753ac..233f48d 100644
>> --- a/collects/scribblings/foreign/types.scrbl
>> +++ b/collects/scribblings/foreign/types.scrbl
>> @@ -401,19 +401,22 @@ procedure with the generated procedure type can be applied in a
>>  foreign thread (i.e., an OS-level thread other than the one used to
>>  run Racket). The call in the foreign thread is transferred to the
>>  OS-level thread that runs Racket, but the Racket-level thread (in the
>> -sense of @racket[thread]) is unspecified; the job of
>> - at scheme[async-apply] is to arrange for the callback procedure to be
>> -run in a suitable Racket thread. The @scheme[async-apply] function is
>> +sense of @racket[thread]) is unspecified; the job of the provided
>> + at scheme[async-apply] procedure is to arrange for the callback procedure to be
>> +run in a suitable Racket thread. The given @scheme[async-apply] procedure is
>>  applied to a thunk that encapsulates the specific callback invocation,
>>  and the foreign OS-level thread blocks until the thunk is called and
>>  completes; the thunk must be called exactly once, and the callback
>> -invocation must return normally. The @scheme[async-apply] procedure
>> +invocation must return normally. The given @scheme[async-apply] procedure
>>  itself is called in atomic mode (see @scheme[atomic?] above). If the
>>  callback is known to complete quickly, requires no synchronization,
>>  and works independent of the Racket thread in which it runs, then
>> - at scheme[async-apply] can apply the thunk directly. Otherwise,
>> - at racket[async-apply] must arrange for the thunk to be applied in a
>> -suitable Racket thread sometime after @racket[async-apply] itself
>> +it is safe for the given
>> + at scheme[async-apply] procedure to apply the thunk directly. Otherwise,
>> +the given @racket[async-apply] procedure
>> +must arrange for the thunk to be applied in a
>> +suitable Racket thread sometime after the given
>> + at racket[async-apply] procedure itself
>>  returns; if the thunk raises an exception or synchronizes within an
>>  unsuitable Racket-level thread, it can deadlock or otherwise damage
>>  the Racket process. Foreign-thread detection to trigger
>> pcp062767pcs:~/plt/collects/scribblings/foreign clements$
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