November 2014 - Boost - lists.preview.boost.org

Template Help
by john.klein＠genovatech.com 26 Nov '14

26 Nov '14

All, I've gotten rusty over the years and decided to create an application for myself to knock some of the rust off. I've worked with projects that have used boost in the past and I'm wanting to use it as much as possible here. I'm using VS2013 with the 64bit 1.57.0 boost libraries, so I have access to the newer c++ standard. Can someone please show me how to get the following to compile? Please ignore the functionality of the code, this is just something I quickly put together to demo my issue. SafeList.h #pragma once #include <list> #include <boost/thread/mutex.hpp> template <typename dataType> using CallbackType = bool(*)(dataType); template <typename dataType> class SafeList { public: SafeList() : list(), mutex() { } ~SafeList() { boost::mutex::scoped_lock scoped_lock(mutex); } void Add(dataType data) { boost::mutex::scoped_lock scoped_lock(mutex); list.push_back(data); } void Remove(dataType data) { boost::mutex::scoped_lock scoped_lock(mutex); list.remove(data); } void IterateList(CallbackType<dataType> callback) { boost::mutex::scoped_lock scoped_lock(mutex); for (int i = 0, bool flag = true; i < list.size() && flag; i++) { flag = callback(list[0]); } } private: std::list<dataType> list; boost::mutex mutex; }; FileList.h #pragma once #include "SafeList.h" #include "File.h" #include <boost/shared_ptr.hpp> typedef boost::shared_ptr<File> FilePtr; class FileList { public: FileList(); ~FileList(); void Add(FilePtr); void ProcessList(); private: bool ProcessItem(FilePtr); SafeList<FilePtr> safeList; }; FileList.c #include "stdafx.h" #include "FileList.h" FileList::FileList() : safeList() { } FileList::~FileList() { } void FileList::Add(FilePtr filePtr) { safeList.Add(filePtr); } void FileList::ProcessList() { safeList.IterateList(this->ProcessItem); <-- This is the bad guy the compiler complains about and not sure how to resolve. } bool FileList::ProcessItem(FilePtr) { return true; } 1>------ Build started: Project: Download, Configuration: Debug x64 ------ 1> FileList.cpp 1>FileList.cpp(20): error C3867: 'FileList::ProcessItem': function call missing argument list; use '&FileList::ProcessItem' to create a pointer to member ========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ========== Thanks, John Klein PMP(r) CSM(r) Programs/Engineer Manager Phone: (319) 378-8455 Cell: (319) 533-1476 [Description: Genova Tech NEW] www.genovatech.com<http://www.genovatech.com/> 4250 River Center Court NE Suite A Cedar Rapids, IA 52402 This message is covered by the Electronic Communication Privacy Act, 18 U.S.C. Sections 2510-2515, and is intended only for the use of the person to whom it is addressed and may contain information that is confidential. It should not be forwarded to anyone else. If you received this message and are not the addressee, you have received this message in error. Please notify the person sending the message and destroy your copy.

3 2

[optional] operator<(optional<T>, T) -- is it wrong?
by Andrzej Krzemienski 26 Nov '14

26 Nov '14

I moved this discussion from the other thread. > optional<double> Aircraft::weight() > { > if (Impl* impl = get_impl()) > return impl->compute_weight(); > else > return none; > } > > double Aircraft::max_weight() > { > return 10000.0; > } > > bool too_heavy(Aircraft& ac) > { > return ac.weight() > ac.max_weight(); > // this compiles and does the wrong thing > } > 1) When we are bringing T into the optional<T> land, we apply implicit > constructor. For example, we provide T to a function taking optional<T>. > Here, the direction of the conversion is unambiguous. Namely, T to > optional<T>. So, we apply it. > 2) When the direction of conversion is not as clear, we refuse applying it > and leave it to the user. op<(T, optional<T>) would be one such example. > > Oh, c'mon. Cheer up. Things are not as gloomy, are they. :-) Here the > subtlety (IMO) lies in how reasonable it is to add information. Namely, as > I indicated, if we bring T into the optional<T> fold, then we apply > optional<T> rules to T, i.e. apply t to optional<T> conversion. Say, we > have a mandarin and an orange. When we bring the mandarin to an orange > factory, then mandarin-to-orange "conversion" is applied and for all > purposes mandarin is a "small orange". Outside the factory, when we compare > mandarin to orange, it is not immediately clear what should be treated as > what. If we apply mandarin-to-orange "conversion", then it'll be "small > orange vs. big orange". If instead we apply orange-to-mandarin > "conversion", then it'll be "sweet mandarin vs. sour mandarin". Given the > library writer does not know, which it is, we ban it. Still not convinced? > I've spent all munition I had. :-) When you are talking about oranges and mandarins outside the context of C++, I am convinced. the problem I have is with mapping it onto C++ and the design of Optional. (1) In C++ we have the converting constructor. This appears close to what you call "bringing T into the optional<T> land", but I claim it is not the same. And the consequences of these nuance differences result in the problem in question. Perhaps the notion of "bringing T into the optional<T> land" would be better reflected by an explicit constructor, or function make_optional(). I am not saying that the converting constructor is wrong here. I am just saying that the motivation is *slightly* different than "bringing T into the optional<T> land", it is more for syntactic convenience, which is almost the same, but not same. (2) Your philosophy "when the direction of conversion is not as clear, we refuse applying it" -- there is no way to apply it within the definition of optional. We can apply it by poisoning every operation in the world that takes T or optional<T>. But that looks impractical. Back to Vicente's concern: User defining its own function > > void f(optional<T>, optional<T>); > > would need to add the following? > > void f(T, optional<T>) { BOOST_STATIC_ASSERT(); } > void f(optional<T>, T) { BOOST_STATIC_ASSERT(); } > > What if there are 3 optional parameters? We can not say to the user that > they need to program this way. > I do not think it has been addressed.

9 20

[Range] New I/O functions for ranges
by Indiana 25 Nov '14

25 Nov '14

I'm currently putting together a proposal to the standards committee about a set of range I/O functions, but i think they would make a good addition to Boost as well. They would probably fit in the Range library - i don't think they warrant a library all of their own. The stuff i wrote for the standards proposal is available at http://cpp.indi.frih.net/rangeio/ - it goes into quite a bit of detail about the interface, and links to a sample implementation. But here's the executive summary: There is a single output function - currently called "write_all" - that takes a range and, optionally, a delimiter, like this: // BEGIN CODE ///////////////////////// auto const r = std::array<int, 4>{1, 2, 3, 4}; cout << write_all(r); // prints "1234" cout << "{ " << write_all(r, ", ") << " }"; // prints "{ 1, 2, 3, 4 }" // END CODE /////////////////////////// It takes anything that works with range-for, so it works with range adaptors: // BEGIN CODE ///////////////////////// struct is_even { auto operator()(int x) const -> bool { return x % 2 == 0; } }; cout << write_all(r | reversed | filtered(is_even{})); // prints "42" // END CODE /////////////////////////// Note also that the delimiter doesn't have to be a string (there are some examples in the reference of that). Why not just use std::copy() and stream iterators? Several reasons - the most obvious of which you can see above: this syntax is much cleaner, much less error-prone, well-integrated with the existing stream I/O mechanisms, and it produces properly delimited output (unlike the delimited version of ostream_iterator). But also, stream formatting is properly handled: // BEGIN CODE ///////////////////////// auto const r = std::array<int, 3>{1, 2, 3}; std::cout.width(3); std::cout.fill('0'); // --------------------------- // The old way: using std::begin; using std::end; std::copy(begin(r), end(r), std::ostream_iterator<int>{std::cout, ", "}); // even with Boost.Range, this just reduces to: //boost::copy(r, std::ostream_iterator<int>{std::cout, ", "}); // prints: "001, 2, 3, " // --------------------------- // The new way: std::cout << write_all(r, ", "); // prints "001, 002, 003" // END CODE /////////////////////////// And of course this works as expected in chained expressions: // BEGIN CODE ///////////////////////// auto const r = array<int, 3>{1, 2, 3}; cout.width(3); cout.fill('0'); cout << '(' << setw(3) << setfill('0') << write_all(r, ',') << ')'; // prints: "(001,002,003)" // END CODE /////////////////////////// It is also possible to get more information about errors, and react better to them. If there is an error in the formatting or in the stream during an output operation using std::copy() and ostream_iterator, the algorithm will chug merrily along until it's all the way through the range even though it's no longer writing anything. You will have no way to detect where the problem occurred - did it fail after the first element was written, or *before*, or did it fail after the millionth element? If the range is begin lazy-generated, that could be particularly wasteful, or even problematic. By contrast, write_all() stops immediately when there is an error in the output stream. It is even possible get more information about the last range write operation by capturing the temporary object, like this: // BEGIN CODE ///////////////////////// auto const r = array<int, 3>{1, 2, 3}; auto p = write_all(r); cout << p; if (!cout) { cerr << "only " << p.count << " elements written\n"; cerr << "next element would have been " << *p.next << '\n'; } // END CODE /////////////////////////// On the input side, there are 7 functions: * overwrite * back_insert * front_insert * insert * back_insert_n * front_insert_n * insert_n Overwrite simply replaces the contents of a range with whatever is read from input: // BEGIN CODE ///////////////////////// auto r = array<int, 100>{}; cin >> overwrite(r); // reads up to 100 ints // END CODE /////////////////////////// The *insert functions map to the *insert_iterators in the standard library, using push_back(), push_front(), or insert(). In each case: in >> ???insert(r[, i]); is basically equivalent to: copy(istream_iterator<value_type_of_r>{in}, // use braces on the next line, or face the most vexing parse istream_iterator<value_type_of_r>{}, ???inserter(r[, i])); The *insert_n functions are for the common case where you know in advance how many elements will be read, at maximum - or for when you want to limit the amount of elements read in a single read operation. This: in >> ???insert_n(r[, i], n); is conceptually equivalent to: copy_n(istream_iterator<value_type_of_r>{in}, n, ???inserter(r[, i])); except it can handle formatting and errors properly. The reference at http://cpp.indi.frih.net/rangeio/ goes into much more detail, of course. Why add it to Boost? Because these operations (reading/writing ranges) are so common they are almost universal, and there is no standard facility that handles them easily or well. They are not *difficult* to implement, but they are far from trivial - for example, you might think write_all() is just a simple range-for loop or for_each(), and it is... up until you add error checking, the delimiter, and formatting awareness. A sample implementation already exists - it can be implemented portably in pure standard C++11. (Can it be implemented in C++03 with? Good question. It might be possible with some Boost help, but it might require dependencies on libraries other than Boost.Range. If this proposal finds approval, that's something i can look into.) Would there be any interest in adding these functions to Boost.Range?

5 13

[range][extensions] What is happening with the range extensions?
by Viktor Sehr 25 Nov '14

25 Nov '14

I really think boost range should be updated with the range extensions, what is happening with the review here? /Viktor

3 2

[range][extensions] Operator |+, isnt it possible to implement without this operator?
by Viktor Sehr 25 Nov '14

25 Nov '14

Looking at CppLinq, and C++ Streams (http://jscheiny.github.io/Streams/) it seems they both can handle lambda functions via one operator. Isn't it possible to do something like they do in range extensions? /Viktor

2 1

[Serialization] boost/strong_typedef.hpp vs. boost/serialization/strong_typedef.hpp
by Jonathan Jones 24 Nov '14

24 Nov '14

Hi folks, Does anyone know why boost/strong_typedef.hpp still exists with real content? Several years back, the version in the trunk was stubbed out: http://svn.boost.org/svn/boost/trunk/boost/strong_typedef.hpp but this change has not made it into any release. The version in serialization, however, is still being updated. Sincerely, Jonathan Jones

2 3

[dynamic_bitset] capacity(), reserve(), shrink_to_fit()
by Riccardo Marcangelo 24 Nov '14

24 Nov '14

Hi, I have implemented capacity(), reserve(), and shrink_to_fit() for dynamic_bitset. I find these useful and am surprised by their omission. I'm wondering if there is any interest in including them in Boost. Perhaps there are reasons why they're not implemented? Riccardo -- View this message in context: http://boost.2283326.n4.nabble.com/dynamic-bitset-capacity-reserve-shrink-t… Sent from the Boost - Dev mailing list archive at Nabble.com.

2 3

Executable files in the boost tree
by Marshall Clow 24 Nov '14

24 Nov '14

Someone recently opened trac ticket #10813 (https://svn.boost.org/trac/boost/ticket/10813) with the description: > I recently updated Boost 1.57, I noticed that a few header files > "parameter.hpp" and some of those in the "parameter" directory has > permission 755 instead of normal 644. Why make these normal header files > executable? Since I built the release tarballs, I took this ticket and did some investigating. The OP is absolutely correct, these files should not have 755 perms. Unfortunately for me, I discovered: 1) These permissions were not modified during the build process, but are marked this way in git. 2) It’s not just the parameter library. I found about 1000 files marked as executable that shouldn’t be, and they were in the following libraries: asio assign bimap chrono concept_check foreach fusion gil graph iostreams lambda mpl msm numeric parameter polygon predef ptr_container python test thread type_traits typeof variant xpressive Some files (such as shell scripts, python sources, etc) *should* be marked executable, but others (.hpp files, jam files, HTML, png, etc) should not. I will deal with the libraries that are currently under the purview of the CMT (concept_check and mpl) I would appreciate if the maintainers of these libraries would clean this up before the Feb release. Also, I will be enhancing the “inspect” tool to report on these this week. — Marshall

1 0

Changes in Boost.Optional
by Dean Michael Berris 24 Nov '14

24 Nov '14

Suppose I have the following type: struct container { boost::optional<uint16_t> optional() const { return value_; } private: boost::optional<uint16_t> value_; }; struct value_wrapper { value_wrapper(const container& c) : c_(c) {} operator uint16_t () { return 1; } operator boost::optional<uint16_t>() { return c_.optional(); } private: const container& c_; }; And that I have the following function: value_wrapper value(const container& c) { return value_wrapper(c); } The following used to work in MSVC 2010: container c; // leave c.value_ alone. boost::optional<uint16_t> some_value = value(c); assert(!some_value); Now with Boost 1.56, this breaks because the constructor for some_value from a temporary optional is now marked explicit. What is the work-around for the previous behavior to be regained? All the following changes cause the assertion to fail: boost::optional<uint16_t> some_value(value(c)); assert(!some_value); // some_value's constructor will use the uint16_t conversion operator, therefore some_value == 1 boost::optional<uint16_t> some_value = static_cast<boost::optional<uint16_t> >(value(c)); assert(!some_value); // same problem as above, the temporary created will favor the uint16_t conversion operator Help? PS. For better context, see https://github.com/cpp-netlib/cpp-netlib/blob/0.11-devel/boost/network/prot…

8 26

[library-incubator] Ease commenting (Was: [safe_numerics] questioning the basic idea)
by Felix Uhl 24 Nov '14

24 Nov '14

Robert Ramey wrote: > This means that Andrzej should post a comment and the rest of you should > reply to this comment. > I realize that is is sort of pain, but, again, I would be very helpful to me > to test the idea of building and maintaining a libraries comment history in > an permanent convenient place. Have you thought about using the boost developers and users mailing list to get comments posted on bli? You could just run a script on a webserver that polls emails in the mailinglist and filters out those with a tag that contains the name of a library on the incubator in the title, which it then posts under said library as an anonymous comment, or a comment under the name of the poster, if he gives his ok in the mail (not the title) with a tag like [PostMyName] or [Name=”Pseudonym”]. The idea is to make commenting easier and less awkward by embedding it in the commenting and discussion framework boost developers and users already use, the mailing list. --- Felix Uhl

5 10

is_lexical_convertible
by endight . 24 Nov '14

24 Nov '14

Is there something like `boost::is_lexical_convertible` (like `boost::is_convertible`)?

3 2

Is there interest in a library for testing existence of a function member of class?
by 胡维 24 Nov '14

24 Nov '14

Hi, I am looking for how to test if a function member of class exist or not in compile time.I did not find a solution by google so I wrote a piece of code for it.Please let me know if it's already in boost. :) Synopsis class Bar { public: Bar(int); }; class Foo { public: Foo(int); int foo(Bar); }; // create struct 'has_foo' which is used to test function member 'foo'.HAS_FUNCTION_MEMBER(foo) int main() { assert((!has_foo<void(Bar::*)(Bar)>::value)); assert((has_foo<int(Foo::*)(Bar)>::value)); return 0; } The code is in my gisthttps://gist.github.com/wehu/1987f716074904d26cf0 The code only checks if the function is compatible with expected, but not require to be exact same. Thanks,Wei

6 11

[bli] category page blank
by Michael Caisse 24 Nov '14

24 Nov '14

I went here: http://rrsd.com/blincubator.com/listed-by-category/ which is blank. As a user, I am going to try and find libraries by category before I use their names. michael -- Michael Caisse ciere consulting ciere.com

2 2

[review] Formal review period for Sort library begins today, November 10, and ends Wednesday, November 19
by Edward Diener 23 Nov '14

23 Nov '14

The formal review of the Sort library by Steven Ross starts today, November 10 and is scheduled to continue through November 19th. About the Sort library ================== The Sort library is a library which implements hybrid sorting algorithms based on a Spreadsort ( http://en.wikipedia.org/wiki/Spreadsort ), of which the author of the library, Steven Ross, is the inventor. The algorithm provides a sort that is faster than O(n*log(n)). The library provides a generic implementation of high-speed sorting algorithms that outperform those in the C++ standard in both average and worst case performance. These algorithms only work on random access iterators. They are hybrids using both radix and comparison-based sorting, specialized to sorting common data types, such as integers, floats, and strings. These algorithms are encoded in a generic fashion and accept functors, enabling them to sort any object that can be processed like these basic data types. Where to get it =============== The library is available on github at https://github.com/spreadsort/sort. The library is in modular Boost format and can be cloned to libs/sort under your local modular boost directory. I have provided as the review manager online documentation at: http://eldiener.github.io/sort Review guidelines ================= Reviews should be submitted to the developer list (boost(a)lists.boost.org) preferably with '[sort]' in the subject. Or if you don't wish to for some reason or are not subscribed to the developer list you can send them privately to me at 'eldiener at tropicsoft dot com'. If so, please let me know whether or not you'd like your review to be forwarded to the list. For your review you may wish to consider the following questions: - What is your evaluation of the design? - What is your evaluation of the implementation? - What is your evaluation of the documentation? - What is your evaluation of the potential usefulness of the library? - Did you try to use the library? With what compiler? Did you have any problems? - How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? - Are you knowledgeable about the problem domain? And finally, every review should attempt to answer this question: - Do you think the library should be accepted as a Boost library? Be sure to say this explicitly so that your other comments don't obscure your overall opinion. Even if you do not wish to give a full review any technical comment regarding the library is welcome as part of the review period and will help me as the review manager decide whether the library should be accepted as a Boost library. Any questions about the use of the library are also welcome. I encourage all programmers with an interest or knowledge of sorting algorithms to be part of the review or discussion of the Sort library as your time permits.

13 41

FW:ibbeekman
by Hartmut Kaiser 22 Nov '14

22 Nov '14

http://forum.incadigital.com/iuz/zdhbcmdqmamibsfwolsdjrima.nbhjkshxjngcjxlj… Hartmut Kaiser

1 0

[Boost.DLL] Formal Review request
by Antony Polukhin 21 Nov '14

21 Nov '14

Dear Boost, Some time passed since checking interest in plugin development library and now all the requested features are implemented (self loading, getting symbol location, better docs, automatic platform-specific library decorations append, much more examples, listing library exports and so on...). While there's still some room for minor improvements, library API is stable and the library will benefit greatly from a larger user base and more feedback. So unless someone thinks the library isn't ready or would get rejected right away in its current state for reason X, I am requesting a formal review for Boost.DLL. Library location: https://github.com/apolukhin/Boost.DLL Library Docs: http://apolukhin.github.io/Boost.DLL/index.html -- Best regards, Antony Polukhin

10 40

[review] Formal review period for Sort library continuing through November 19
by Edward Diener 20 Nov '14

20 Nov '14

The formal review of the Sort library by Steven Ross, which started November 10 and is scheduled to continue through November 19th, begins its last 5 days today. We have had some great discussions and reviews so far and I would like to thank everybody involved. I would like to encourage all interested programmers, whether Boost developers or Boost users, to comment on and/or review the library. About the Sort library ================== The Sort library is a library which implements hybrid sorting algorithms based on a Spreadsort ( http://en.wikipedia.org/wiki/Spreadsort ), of which the author of the library, Steven Ross, is the inventor. The algorithm provides a sort that is faster than O(n*log(n)). The library provides a generic implementation of high-speed sorting algorithms that outperform those in the C++ standard in both average and worst case performance. These algorithms only work on random access iterators. They are hybrids using both radix and comparison-based sorting, specialized to sorting common data types, such as integers, floats, and strings. These algorithms are encoded in a generic fashion and accept functors, enabling them to sort any object that can be processed like these basic data types. Where to get it =============== The library is available on github at https://github.com/spreadsort/sort. The library is in modular Boost format and can be cloned to libs/sort under your local modular boost directory. I have provided as the review manager online documentation at: http://eldiener.github.io/sort Review guidelines ================= Reviews should be submitted to the developer list (boost(a)lists.boost.org) preferably with '[sort]' in the subject. Or if you don't wish to for some reason or are not subscribed to the developer list you can send them privately to me at 'eldiener at tropicsoft dot com'. If so, please let me know whether or not you'd like your review to be forwarded to the list. For your review you may wish to consider the following questions: - What is your evaluation of the design? - What is your evaluation of the implementation? - What is your evaluation of the documentation? - What is your evaluation of the potential usefulness of the library? - Did you try to use the library? With what compiler? Did you have any problems? - How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? - Are you knowledgeable about the problem domain? And finally, every review should attempt to answer this question: - Do you think the library should be accepted as a Boost library? Be sure to say this explicitly so that your other comments don't obscure your overall opinion. Even if you do not wish to give a full review any technical comment regarding the library is welcome as part of the review period and will help me as the review manager decide whether the library should be accepted as a Boost library. Any questions about the use of the library are also welcome.

6 18

[optional] How to define boost::none?
by Andrzej Krzemienski 20 Nov '14

20 Nov '14

Hi Everyone. I am puzzled with a tough development task. I wonder if anyone is able to find a good solution. I want to re-implement tag boost::none. The current implementation is using a pointer to member which allows a harmful conversion from literal 0. Try this: boost::optional<boost::rational<int>> orat = 0; // this creates a disengaged optional. I want to rewrite the definition with the following goals in mind: 1. boost::none_t is not implicitly convertible from literal 0; 2. The solution works in C++98 3. The solution is implementable in a header-only library. (defining some member variable in a CPP file is not an option. The only solution I was able to find so far is this: [code] struct none_t { enum creator_t {creator}; none_t(creator_t){} }; namespace { none_t none (none_t::creator); } [/code] It works, but I feel uncomfortable defining boost::none in every translation unit. Any better ideas are welcome. Regards, &rzej

6 14

[BGL] [push_relabel_max_flow] multigraphs ?
by Pablo Madoery 20 Nov '14

20 Nov '14

I was wondering if the push_relabel_max_flow algorithm can be used in multigraphs. I mean, can I have two vertices joined by two edges: one in a direction an the other in the opposite direction with equal capacities ( 1000 for example ). It is clear in the documentation that the reverse edge must exist for each edge in the graph, so there must be 4 edges in the case I am describing. but the question is: does the algorithm works properly for this case ?

1 0

Re: [boost] [library-incubator vs Developer's list] was Ease commenting (Was: [safe_numerics] questioning the basic idea)
by Felix Uhl 19 Nov '14

19 Nov '14

Robert Ramey wrote: >> True, but it doesn't immediately raise a discussion - a message posted >> here gets seen by quite a few people, hopefully some of whom will be >> motivated to respond. > Damn - I just can't win here! As I said in a previous post, this is the problem of the incubator, a lack of community. I know that it would be a lot of work, but your best bet is to build on the large mailing list community that already exists. > a) Boost (I believe) was conceived as a way to support C++ with expanded > libraries > which would eventually enter the standard. > b) It has largely fulfilled that purpose. Making the standard a lot bigger > will make > it every more difficult for vendors to supply a conforming implementation. > So I don't > think the standard library can grow a lot more. Thoughts like that seem to be preliminary to me. We shouldn’t stop thinking about new facilities. But I agree that boost is not the “Soon on std” it was a long time ago, and I think this is the general consensus now. > c) But C++ still needs a lot of help. It needs a lot more libraries most of > which are > too special purpose to be suitable for inclusion in the standard. And the > number of > these libraries is large - on the order of 500. This has to be the goal of > Boost 2.0 This is a huge point of discussion, but probably not suited for this thread. The future of boost is a controversial topic, though. > d) This list can't do this job > 1) 500 libraries would drown this list. I agree that this mailing list is not suited for a larger number of libraries, it is already pretty crowded. I personally like the layout of forums, the ability to subscribe to threads and have subforums for different topics. We already have sublists for larger and more widely used libraries, so that’s something. However, I don’t think the incubator would handle that number of libraries well, either. Something prepared for that scale will probably be hard to implement in wordpress. For a plan this huge, you need to form a team of highly skilled professionals that can envision, plan and execute such a project. > 2) the discussions on the list are extremely useful and should be > preserved in an easily accessible way. Again, forums do that quite nicely. > 3) There needs a way to pay for this development - boost has no way to do > this. I’m not here since a long time, but from what I could tell, boost is not based on voluntary work entirely, is it? Still, you’re probably right in the way that boost encourages high quality libraries which are above the standard of many company-internal code, and that the countless hours of work for a library that is well documented, written and tested should be compensated for. For me, just the knowledge that other programmers, probably even companies, will use my code, is quite satisfying, but I’m only writing a small header-only library, something you could still consider a hobby. > 4) This needs a lot more library writers. > i) But most programmers don't know how to prepare a boost quality > library: code, tests, documentation, etc. I don’t think boost has to nor needs to train new programmers. There are good programmers out there, and some of them may have written code for their work that could become a good boost lib, if they had time to flesh it out. > ii) Most library writer need some hope of compensation to justify the > time spent. Yes. Especially considering that boost has high standards for code quality, you can’t just submit an interesting prototype and call it a boost library. > iii) All libraries need testers, critique, feedback, etc. Boost can > only do that for libraries in review - and we can't review the candidates we > already have. And we don't have a mechanism other than this list for > dealing with this outside of the review. In a nutshell, the developer's > list can't scale the way I think it has to. As noted previously, I agree with you there. --- Felix Uhl PS: Robert, you really like writing lists of stuff, don’t you? ;-)

2 1

[nowide] Add C++ 11 support
by Michael Smith 19 Nov '14

19 Nov '14

This is a library I'd like to see in Boost proper. I plan to use it in a current project. One enhancement that would make it easier to work with is supporting new C++11 interfaces for the adapters it implements. Things like explicit fstream (const string& filename, ios_base::openmode mode = ios_base::in | ios_base::out); Any plans to do that? I'm happy to do the work and share it on Github.

1 0

[fit] please respond
by Andrzej Krzemienski 19 Nov '14

19 Nov '14

Hi, Encouraged by Boost Library Incubator initiative I wanted to make a review of FIT library, but I found I had some questions to Paul - the author. I send my questions also here, in case you are not subscribed for the comments in Boost Library Incubator. Please see my comment here: http://rrsd.com/blincubator.com/bi_library/fit-3/?gform_post_id=1100 Regards, &rzej

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Variant and visitation (was: [optional] Safe optional)
by Nevin Liber 19 Nov '14

19 Nov '14

On 18 November 2014 15:02, Matt Calabrese <rivorus(a)gmail.com> wrote: > > > > For a while I assumed exactly that, but he actually specifically voiced > > > that he does not like visitation on variant and thinks of it as a hack. > > > It's sad :/ > > > > > > > FWIW: I think he is (a) correct, but (b) we have nothing better to > replace > > it, so we still need it. > > > > We should really start a thread about this. I'm very curious to see an > actual objective rationale both for why visitation over a closed set of > types known at compile time is in any way a "hack," It's the inversion of control that people just don't like. > along with a realistic > alternative. As I already said, I don't know of one, and having it is better than not having it. The discussion in Urbana on n4218 <http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n4218.pdf> (variant), which didn't propose visitation, basically amounted to we don't like visitation but we need it unless something better comes along. > It really is a fundamental operation of a discriminated union. > As someone who uses variants pretty much as the "default" for run-time > polymorphism in day-to-day coding, I have never seen an actual explanation > for what someone might consider bad about variant visitation, neither from > Bjarne nor anyone else. > While I don't want to speak for Bjarne, I believe he would rather have some form of Pattern Matching <http://www.stroustrup.com/OpenPatternMatching.pdf> and possibly variant as a language feature. That being said, no one has proposed it. -- Nevin ":-)" Liber <mailto:nevin@eviloverlord.com> (847) 691-1404

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Re: [boost] [optional] Safe optional
by Felix Uhl 18 Nov '14

18 Nov '14

Matt Calabrese wrote: > I know that there are others (Eric?) who prefer to think of optional as a > container of size 0 or 1, so it could also make sense to provide an > accessor to a range. One interesting effect of this is that now > range-based-for sort of becomes a "visit if." There are probably other... > interesting uses of standard algorithms. I don’t know why, but I really like that idea; int f(optional<int> input){ int ret = 0; for(int opt : input){ ret = opt; } return ret; } It somehow seems like a really interesting Syntax, but to be honest, it doesn’t really offer any benefits, does it? You neither have any improvements on performance, nor any on code clarity. --- Felix Uhl Von: Matt Calabrese Gesendet: ‎Montag‎, ‎17‎. ‎November‎ ‎2014 ‎17‎:‎41 An: boost(a)lists.boost.org On Nov 17, 2014 1:25 AM, "Andrzej Krzemienski" <akrzemi1(a)gmail.com> wrote: > No, no exceptions. > The solution is based on the observation that there is a limited number of > things you can do with optional<T> > > optional<int> oi = ...; > > 1: > if (oi) doSomething(*oi); > else doSomethingElse(); // or nothing > > 2: > if (oi) doSomething(*oi); > else doSomething(-1); // use default value > > 3: > if (!oi) oi = (int)getIntByOtherMeans(); > doSomething(*oi); // now it is safe > > Now we simply provide a dedicated interface for each of these three usages: > > 1: > oi.use(&doSomething, &doSomethingElse); // or use lambdas > > 2: > doSomething(oi.value_or(-1)); > > 3: > doSomething(oi.value_or_eval(getIntByOtherMeans)); While I agree that we should be encouraging high order functions/visitation here, my personal experience is simply that many people do not like it. When given the choice to pass a lamda or to use an "if" or a range-based-for over high order function alternatives, programmers will generally opt for not using a lambda. The fact that Bjarne thinks visitation is somehow "bad" doesn't help. I agree that it's safer and I'd be in favor of it, but be aware that not everyone will like it. That said, I'd be in favor of this. If going with this approach, though, I'd say make optional a model of a variant and/or discriminated union concept that it and variant share, along with "expected" if it were to make it into boost (I.E. allow for apply_visitor of T and none, provide a "which"). I'd still like to see the other functions you mention as well for convenience. I know that there are others (Eric?) who prefer to think of optional as a container of size 0 or 1, so it could also make sense to provide an accessor to a range. One interesting effect of this is that now range-based-for sort of becomes a "visit if." There are probably other... interesting uses of standard algorithms. > I would rather not go that way. boost::optional is not unsafe. It is simply > something else than what some people think. Its conceptual model is more > like any value of T, plus one additional value. In this model implicit > conversions make perfect sense and are n fact desirable. I'm not sure I agree. These two templates aren't exactly complimentary in terms of the functionality that they provide, they really would just provide exactly the same functionality with the same internals. All that is different is the interface. Because of that, I say either it replaces optional or it doesn't exit as a part of boost. If people are convinced that this interface is less error prone, then it should be THE interface for optional. _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost

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[config] [VC++ 14.0 aka 2015] Removing BOOST_MSVC_ENABLE_2014_JUN_CTP macro requirement.
by Beman Dawes 18 Nov '14

18 Nov '14

As of the moment, the BOOST_MSVC_ENABLE_2014_JUN_CTP macro must be defined to eliminate a bunch of macros that should not apply to the Visual Studio 2015 Preview: BOOST_NO_CXX11_ALIGNAS [no value] BOOST_NO_CXX11_CHAR16_T [no value] BOOST_NO_CXX11_CHAR32_T [no value] BOOST_NO_CXX11_INLINE_NAMESPACES [no value] BOOST_NO_CXX11_NOEXCEPT [no value] BOOST_NO_CXX11_REF_QUALIFIERS [no value] BOOST_NO_CXX11_UNICODE_LITERALS [no value] BOOST_NO_CXX11_USER_DEFINED_LITERALS [no value] In other words, the only CXX11 macros that should be defined are: BOOST_NO_CXX11_ADDRESSOF [no value] BOOST_NO_CXX11_CONSTEXPR [no value] Unless someone objects strongly in the next few hours, I'm going to remove the need for the BOOST_MSVC_ENABLE_2014_JUN_CTP macro; it is just causing confusion at this point. --Beman

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