Here is the latest OCaml Weekly News, for the week of June 28 to July 05, 2016.
Archive: https://sympa.inria.fr/sympa/arc/caml-list/2016-06/msg00139.htmlDeep in this thread, Jeremy Yallop said:
> It is hard for me to judge because I came through RWO, but it appears to me > that the lack of consensus on standard library comes up pretty quickly. I think the standard library situation is much less of a concern than it once was, now that it's easy to distribute small OCaml packages and manage dependencies. In the past distribution difficulties discouraged dependencies: for example, even though many people prefer the design of ocaml-re and ocaml-pcre to the regular expression facilities in the standard library, the administrative overhead of an additional dependency made the standard library the easier choice overall. In that situation it's desirable for the standard library to be large and featureful. Nowadays there's much less benefit to having regular expression support in the standard library, since depending on ocaml-re or ocaml-pcre is just a matter of adding a line to an opam file and a few lines to the build configuration. The standard library still has a useful role to play, since it's easier to make libraries interoperate if they can communicate via common types, and several recent and proposed changes have that kind of role in mind. For example, the latest release of OCaml added a 'result' type to the standard library, which was previously defined in incompatible but essentially equivalent ways in several libraries: https://github.com/ocaml/ocaml/pull/147 and there's a proposal for adding iterators to various container types for the next release currently under discussion: https://github.com/ocaml/ocaml/pull/635Dean Thompson then said and Yaron Minsky replied:
> From my understanding so far, it seems to me that mixing and matching Core > and not-Core would be tough? Everything from result types to Lwt vs Async? > Given the inspirational and educational power of Real World OCaml, many > newcomers will face this issue. A few thoughts: As Anil said, we're working on an updated RWO, which should resolve the camlp4 issue. As for mixing and matching between libraries that do and don't depend on Core, there's actually little difficulty here. Core sticks to the standard interchange types (array, string, option, list, char, and now result) that are provided by the stdlib, so whether you use Core (or Core_kernel) becomes more a matter of personal preference, and shouldn't hinder interoperability. One remaining problem with Core is the minimal executable size, which is currently much bigger if you use Core. We're considering some work in three next few months to make this much better. Async and Lwt are a real problem. They provide very similar functionality, and mixing and matching between two schedulers is not so easy. I'd love to see some resolution here, but it's not clear what the solution would be. Perhaps once we resolve the executable size issues of Core, there will be more appetite for some kind of merger of the two libraries. In the meantime, we're highly committed to continuing development and support for Async.Ivan Gotovchits then said:
The solution would be to use the same approach as with standard types. We need a common base inductive type for `Lwt.t` (aka `Ivar.t`), which will represent a value which is defined in some point in the future (hence a `future` is a good name). Another type is for capturing a concept of a variable that can have multiple values in the future, that is represented as `Lwt_stream.t` or `Pipe`. Currently in both Lwt and Async the main thread type is tightly coupled with the underlying implementation, especially in Async (Lwt.t can be easily decoupled).Yaron Minsky then said:
I'm not at all sure that the decoupling is possible or wise for Async. My intuition is that this is too complex of a problem with too much need for careful optimization to be able to have a simple, shared generic data structure for this. The solution that seems most plausible to me is to settle on one implementation, and port the API of one library to run on top of the other. There was indeed an experiment in this direction that was done by Jeremie Dimino: https://github.com/janestreet/lwt-async That said, until we resolve the binary size issues with Core and therefore Async, I doubt that this solution would be appealing to the full community of lwt users.Hendrik Boom asked and Yaron Minsky replied:
> What are the conceptual differences between Async and lwt? Does either > of them manage to take advantage of a shared-heap multicore system? The conceptual differences are pretty thin; there are some error handling differences, but they're not huge. As for the shared heap question: Async greatly improves the programmers ability to reason about concurrent code by providing clear bounds on when interleaving can happen. In particular, a given job scheduled to run as part of Async can never be interrupted by another async job. That means interleavings can effectively only happen where you use a bind operator to string two closures together, and so one is rarely exposed to race conditions. That means that Async program typically don't need to think much about locking, and race conditions stop being your primary source of bugs. Using Async in the context of shared heap parallelism gives up these guarantees, and puts you back in mutex/sempahore/condition-variable hell. My guess is that we'll end up taking advantage of the multicore GC by running multiple Async schedulers, one per domain (e.g., OS thread), and having carefully written primitives for sharing data-structures and efficiently sending immutable messages between these domains. But I think just freely scheduling Async jobs across multiple physical threads seems like a disaster from the point of view of producing comprehensible, reliable code.
Archive: https://sympa.inria.fr/sympa/arc/caml-list/2016-07/msg00015.htmlhugo announced:
Here are links from many OCaml blogs aggregated at OCaml Planet, http://ocaml.org/community/planet/. Minimising the virtual machine monitor https://hannes.nqsb.io/Posts/Solo5 Behavioural types http://kcsrk.info/ocaml/types/2016/06/30/behavioural-types/ Software Engineer (ClojureScript, F#) at Xledger (Full-time) https://functionaljobs.com/jobs/8934-software-engineer-clojurescript-f-at-xledger FP Meetup: OCaml, Facebook and Docker at Jane Street https://ocaml.io/w/Blog:News/FP_Meetup:_OCaml,_Facebook_and_Docker_at_Jane_Street
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