Here is the latest OCaml Weekly News, for the week of December 13 to 20, 2016.
Archive: https://sympa.inria.fr/sympa/arc/caml-list/2016-12/msg00046.htmlVasilis Papavasileiou announced:
We are very happy to announce the release of Ocsigen Eliom 6.0 , which follows the recent releases of Ocsigen Server 2.8  and Ocsigen Js_of_ocaml 2.8.x . New features include a friendlier service API that retains the expressive power of our service system. Additionally, Eliom can now be used to build cross-platform Web/mobile applications (Android, iOS, ...). ## What is Eliom? Eliom is a framework for developing client/server web applications. Both the server and the client parts of the application are written in OCaml, as a single program. Communication between server and client is straightforward, e.g., one can just call a server-side function from client-side code. Eliom makes extensive use of the OCaml language features. It provides advanced functionality like a powerful session mechanism and support for functional reactive Web pages. ## Friendly service APIs Services are a key concept in Eliom, used for building the pages that are sent to the user, for accessing server-side data, for performing various actions, and so on. Eliom 6.0 provides a friendlier API for defining and registering services, thus making Eliom more approachable. The new API makes extensive use of OCaml's GADTs, and provides a single entry-point that supports most kinds of services (`Eliom_service.create`). For more information, refer to the Eliom manual . ## Mobile applications Eliom 6.0 allows one to build applications for multiple mobile platforms (including iOS, Android, and Windows) with the same codebase as for a Web application, and following standard Eliom idioms. To achieve this, we have made available the Eliom service APIs on the client . Thus, the user interface can be produced directly on the mobile device, with remote calls only when absolutely necessary. To build an Eliom 6.0 mobile application easily, we recommend that you use our Ocsigen Start  project, which provides a mobile-ready template application. Ocsigen Start is currently available in OPAM as a preview, with an 1.0 release coming soon. ## Compatibility Eliom 6.0 supports the last 3 major versions of OCaml (4.02 up to 4.04). Additionally, Eliom is compatible with and builds on the latest Ocsigen releases, including Ocsigen Server 2.8, Js_of_ocaml 2.8.x, and TyXML 4.0.x. ## Future The Ocsigen team is busy working on new features. Notably, we are developing an OCaml compiler  specifically tuned for Eliom. Additionally, we are planning a transition to the Cohttp backend. ## Support - Migration guide: https://ocsigen.org/eliom/Eliom60 - Issue tracker: https://github.com/ocsigen/eliom/issues - Mailing list: https://sympa.inria.fr/sympa/info/ocsigen - IRC: `#ocsigen` on `irc.freenode.net` : https://github.com/ocsigen/eliom/releases/tag/6.0.0 : https://github.com/ocsigen/ocsigenserver/releases/tag/2.8 : https://github.com/ocsigen/js_of_ocaml/releases/tag/2.8.3 : https://ocsigen.org/eliom/dev/manual/server-services : https://ocsigen.org/eliom/manual/clientserver-services : https://github.com/ocsigen/ocsigen-start : https://github.com/ocsigen/ocaml-eliom
Archive: https://sympa.inria.fr/sympa/arc/caml-list/2016-12/msg00073.htmlIvan Gotovchits asked:
The tabulation boxes are marked as deprecated since 4.03.0. I've tried to google for any reasons that justify the removal but found only a note by Pierre Weis in the Matis issue tracker: The proposed printf-like syntax is fine, but tabulation boxes are now deprecated. Indeed, tabulation boxes interaction with other pretty-printing boxes have never been sorted out and tabulation boxes usage is orthogonal to the rest of the Format module. If considered useful, tabulation boxes could be implemented out of the Format module. First of all the tabulation boxes can't be implemented outside of the format module since the tab stops are actually stored in the stack of tabulation boxes. If this data field would be removed from the formatter we will need to pass an extra argument to all pretty-printers that use the tabulation break, or use some global variable. Neither solution can be considered acceptable. Speaking about the usefulness. The tabulation boxes are useful for printing assembly outputs. And since compiler writing is sort of an application area for OCaml, it shouldn't be considered as a rare case. It is also very useful for printing Fortran code, that can be considered an assembler for the numeric computing. It also just allows printing nicely formatted texts, that it the main purpose of the Format library. As an example, tabulation boxes are used in BAP and CIL frameworks. To summarize, the deprecation will eventually make few project non-compilable. And there is no clear substitution for the deprecated feature. Given that, I would like to hear the justifications for the deprecation of tabulation boxes and suggested workarounds. One possible workaround, that I could see, is making the `formatter` type extensible with existential boxes or, more generally, with existential attributes. In that case, we will indeed be able to implement tabulation boxes outside of the format module. Best wishes, Ivan Gotovchits : https://caml.inria.fr/mantis/view.php?id=4665Gabriel Scherer replied:
You may be interested in the discussion https://github.com/ocaml/ocaml/pull/229 which discussed a few ways in which the proposed tabulation interface may be inconvenient. It is after this discussion that Pierre Weis decided to deprecate tabulation boxes -- I believe that the reason is that tabulation and formatting never mixed very well. Note that if you can decide in advance a maximal size for a given "column" of your formatted output, you can use the left or right-justification features of formatting conversions to print aligned text: let data = [("x", "foo"); ("loop", "bar")] let () = print_newline (); data |> List.iter (fun (lab, instr) -> Printf.printf "%5s: %s\n" lab instr) (* x: foo loop: bar *) let () = print_newline (); data |> List.iter (fun (lab, instr) -> Printf.printf "%-5s: %s\n" lab instr) (* x : foo loop : bar *) let () = let len = List.fold_left (fun m (lab, _) -> max m (String.length lab)) 0 data in print_newline (); data |> List.iter (fun (lab, instr) -> Printf.printf "%*s: %s\n" len lab instr) (* x: foo loop: bar *)Ivan Gotovchits then said:
Well, the discussion literally says, we don't understand tabulation, and it looks like nobody is using it, so let's just throw it away :) We're using tabulation, and they are quite useful. Yep, I agree, that the interface for setting the marks is kind of awkward, it would be nice if there would be a `pp_setup_tabs : _ formatter -> int list -> unit` function, that would push into the stack a new tabular box with the specified tabulations. What concerning your solution with the alignment, it is less general and doesn't work in our case. First of all, the pretty printing functions, that are printing into the columns are not specified with `%s`, but with `%a` (e.g., address, memory string, assembly string). Second, the printing functions are not actually defined in the same module. The tabs are initialized in the frontend, that defines it based on the architecture (address size, maximum length of instruction, etc), and pretty printers are registered separately, and they just rely on a fact, that we have three columns, the first is for address, the second is for memory, then assembly, etc). This design simplifies the actual instruction printers, by consolidating the common code in the formatter setup procedure. So, it is still not clear to me, why the tabulations are wrong. If they do complicate the code base and raise the support cost, then it is understandable, why you would like to remove it from the standard library. But in this case, it would be nice, to move this code out as a separate library, as just removing a feature, that was in the language for years (I would say even forever, if we will start the history from caml-light), without providing any substitution is... not nice :) : http://caml.inria.fr/pub/docs/manual-caml-light/node15.5.html
Here are links from many OCaml blogs aggregated at OCaml Planet, http://ocaml.org/community/planet/. vile 9.8s http://blog.0branch.com/posts/2016-12-18-vile-9.8s.html Merlin promoted to headline OCaml project https://ocaml.io/w/Blog:News/Merlin_promoted_to_headline_OCaml_project Coq 8.6 is out https://coq.inria.fr/news/134.html
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