Pike-devel August 2019

pike-devel@lists.lysator.liu.se

7 participants
18 discussions

Pike conference 2019
by Tobias S. Josefowitz 30 Aug '19

30 Aug '19

Hi, we invite you to this year's Pike developer conference on the weekend of the 2nd and 3rd of November 2019. Opera will host the conference in its offices in Linköping. On Saturday and Sunday we meet at the Opera offices (Repslagaregatan 21) starting from 10:00. Just call "Opera Software" using the fancy door-bell-replacement technology at the entrance (or follow instructions as posted on the door, if any). Even though asking for this has traditionally proved somewhat pointless with our crowd, why don't you drop me an email to let me know should you want to join. On Friday the 1st of November 2019, Roxen invites everyone who is already in town and available at 15:00 to the traditional pre-conference fika at the Roxen office at S:t Larsgatan 22a. If you want to schedule an item on the conference agenda or have any other questions, please just send me an email. On behalf of the 2019 conference committee, Tobi

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Broken online documentation
by Tomasz Jamroszczak 27 Aug '19

27 Aug '19

There's no System.Tiem in the documentation. I can access it via Google Search cache: https://webcache.googleusercontent.com/search?q=cache:5nqNuHyJgzAJ:https://… Best Regards, Tomasz Jamroszczak

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Re: Comments/thoughts requested: Generators and async functions in Pike
by Chris Angelico 27 Aug '19

27 Aug '19

On Tue, Aug 27, 2019 at 3:26 AM Henrik Grubbström (Lysator) @ Pike (-) developers forum <10353(a)lyskom.lysator.liu.se> wrote: > > > Pike now (8.1) has a decent promise/future subsystem. It's always had > > great handling of multiple asynchronous operations (GUI, socket, time > > delay, etc) with the convenience of just returning -1 from main. > > Interested in people's opinions on whether it would be of value to > > introduce generators and (built on them) asynchronous functions. > > > > I'm borrowing terminology heavily from Python and ECMAScript here, and > > both of them have drawn from prior art. > > > > A *generator function* is a function that can be partially run, then > > set aside until resumed. Effectively, its stack frame can be > > encapsulated in an object for future use. It would look something like > > this: > > > > int get_numbers() { > > write("Starting\n"); > > yield 1; > > write("Continuing\n"); > > yield 2; > > write("Finishing\n"); > > return 3; > > } > > > > Calling get_numbers would prepare an execution context, but not > > actually begin running the function at all. The caller would get back > > a *generator object*. Asking this generator object to produce its next > > value would begin executing the function, triggering the call to > > write, and would stop at the first yield point, returning that value > > (1). Asking for another value resumes the function, triggering the > > second write, and returns the next yielded value. The third time you > > request a value, it would run the function to completion, and report > > that it returned (not yielded) 3. > > > > (The types yielded don't have to match the type of the return value. > > I'm not sure if there's a good way to declare the yielded types, or if > > it's best to just assume 'mixed'.) > > Not matching the declared type seems like a bad idea. They're two quite separate types, and there's currently no way to declare that distinction. The type yielded and the type returned could be completely different. For example, when being used for asynchronous code, the yielded type would be some sort of awaitable (a Concurrent.Future or similar), and the returned type would be the actual data to be produced. > > A generator object would be an Iterator, allowing you to loop over the > > yielded values easily: > > This is a separate issue. Note that iterators have both indices and values. Yes, I'm aware of that; would it be a problem if the indices are just all zero? Generators don't have any useful concept of "indexing". > > foreach (get_numbers() ;; int num) > > > > The 'yield' keyword would be an expression/operator, allowing you to > > send a value back into the generator function as the result of the > > yield expression. > > This seems to be something entirely different?? It's the way to elevate generators to coroutines. You produce a value out of the generator, and then either get one back in, or just get a zero that you ignore. > Anyway, I have a proof of concept implementation of the first use: > > --- generator_test.pike --- > > continue int foo(int start, int end) > { > while (start <= end) > continue return start++; > } > > int main(int argc, array(string) argv) > { > function(:int) bar = foo(4, 8); > > int i; > do { > i = bar(); > if (zero_type(i)) break; > werror("%d\n", i); > } while (1); > } > > --------------------------- > > $ ./pike generator_test.pike > 4 > 5 > 6 > 7 > 8 > 0 > > Note that the ending 0 is due to the implicit return 0 at the end of > Pike functions. Yes, which is why the returned value can plausibly be different from the "continue return" intermediate values - you don't use them the same way. Going back to my original async I/O example and recasting it into your syntax: string show_channel_info(string name) { int id = continue return get_channel_id(name); mapping data = continue return query_channel(id); write("Status: %s\n", data->status); mapping stream = continue return get_stream_info(id); if (stream) return sprintf("%s is online, %s", name, stream->uptime); return name + " is offline."; } The intermediate values would be Concurrent.Futures; the caller would get one of them, wait on it, and then send the returned value back in. The final return value is a string. ChrisA

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Use of ::_destruct() in arbitrary objects
by Chris Angelico 26 Aug '19

26 Aug '19

In digging into a problem with Protocols.HTTP.Promise, I came across an issue with inheritance and destructors. #ifdef HTTP_PROMISE_DESTRUCT_DEBUG # define PROMISE_DESTRUCTOR \ protected void _destruct() { \ werror("%O()._destruct()\n", object_program(this)); \ } #else # define PROMISE_DESTRUCTOR #endif Activating this debug flag actually prevents the parent destructors from being called. And simply adding ::_destruct() into there doesn't work either, as that will break for anything that DOESN'T have a _destruct in its parent. How can this be solved generically? The symbol ::_destruct simply can't be looked up (at compile time) if the parent doesn't have one. ChrisA

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Comments/thoughts requested: Generators and async functions in Pike
by Chris Angelico 26 Aug '19

26 Aug '19

Pike now (8.1) has a decent promise/future subsystem. It's always had great handling of multiple asynchronous operations (GUI, socket, time delay, etc) with the convenience of just returning -1 from main. Interested in people's opinions on whether it would be of value to introduce generators and (built on them) asynchronous functions. I'm borrowing terminology heavily from Python and ECMAScript here, and both of them have drawn from prior art. A *generator function* is a function that can be partially run, then set aside until resumed. Effectively, its stack frame can be encapsulated in an object for future use. It would look something like this: int get_numbers() { write("Starting\n"); yield 1; write("Continuing\n"); yield 2; write("Finishing\n"); return 3; } Calling get_numbers would prepare an execution context, but not actually begin running the function at all. The caller would get back a *generator object*. Asking this generator object to produce its next value would begin executing the function, triggering the call to write, and would stop at the first yield point, returning that value (1). Asking for another value resumes the function, triggering the second write, and returns the next yielded value. The third time you request a value, it would run the function to completion, and report that it returned (not yielded) 3. (The types yielded don't have to match the type of the return value. I'm not sure if there's a good way to declare the yielded types, or if it's best to just assume 'mixed'.) A generator object would be an Iterator, allowing you to loop over the yielded values easily: foreach (get_numbers() ;; int num) The 'yield' keyword would be an expression/operator, allowing you to send a value back into the generator function as the result of the yield expression. The awesomeness of this becomes more apparent when combined with Concurrent.Future objects. An asynchronous function would be a generator which yields Futures until it is ready to return a value. Calling such a function automatically returns a ready-to-go Future, set up such that it is automatically transform_with'd the next yielded Future, or transform'd into the returned value. It would be used somewhat thus: void show_channel_info(string name) { int id = yield get_channel_id(name); mapping data = yield query_channel(id); write("Status: %s\n", data->status); mapping stream = yield get_stream_info(id); if (stream) write("%s is online, %s\n", name, stream->uptime); else write("%s is offline.\n", name); } This is WAY more readable than the equivalent with a bunch of lambda functions to capture the intermediate values. Thoughts? Concerns? Questions? ChrisA

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Re: SSL cert for pike.lysator.liu.se has expired
by Chris Angelico 23 Aug '19

23 Aug '19

On Fri, Aug 23, 2019 at 11:59 PM Peter Bortas @ Pike developers forum <10353(a)lyskom.lysator.liu.se> wrote: > > I guess that's me. Fixed. Thanks! I was doing some Pike coding on live-stream today and one of my viewers mentioned it. Appreciate the quick fix! ChisA

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SSL cert for pike.lysator.liu.se has expired
by Chris Angelico 23 Aug '19

23 Aug '19

Going to https://pike.lysator.liu.se/ shows a big warning about the certificate having expired. Who's in charge of this? ChrisA

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Broken online documentation
by Tomasz Jamroszczak 02 Aug '19

02 Aug '19

When I look for for "Timer" in the "Site search" box on http://pike.lysator.liu.se/generated/manual/modref/ex/predef_3A_3A/System.h… page, I can see link to System.Timer http://pike.lysator.liu.se/generated/manual/modref/ex/predef_3A_3A/System/T… but it returns HTTP 404. Best Regards, Tomasz Jamroszczak

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Pike-devel August 2019