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[wave] trace doesn't output errors.
by Adrian_H 07 May '13

07 May '13

I've got a really annoying and difficult to track down PP error. I'm attempting to use wave to see the expansion, but it is slow going. The output is correct, in both the g++ PP and the wave parser. g++ states: *error: macro "BOOST_PP_SEQ_ELEM_III" requires 2 arguments, but only 1 given*, wave states *warning: too few macro arguments: BOOST_PP_SEQ_ELEM_III*, but when I try using the tracer it doesn't say when this occurs. Is it possible to turn this on? Or is there no 'on' and I have to go into the wave code and code it on? If the latter, where would I do this? Thanks, Adrian -- View this message in context: http://boost.2283326.n4.nabble.com/boost-wave-trace-doesn-t-output-errors-t… Sent from the Boost - Dev mailing list archive at Nabble.com.

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Git Modularization Ready for Review
by Niall Douglas 07 May '13

07 May '13

> After substantial work, including massive changes by me and Daniel Pfeifer to > KDE's svn->Git conversion tool, we have captured every Boost SVN commit in a > Git repository. You can view the results at > > http://github.com/boostorg > http://bitbucket.org/boostorg > > Daniel and I are ready to accept your feedback on the results of modularization, > and especially your pull requests containing edits to the ruleset. I will the > steering committee to establish a formal review period, though. I'm a bit confused. This looks like a hand written map of parts of Boost SVN onto multiple GIT repos. Am I understanding correctly? I'm far more confused as to why? Surely the conventional approach is to convert a SVN repo to GIT. Then people hive off their particular bits into submodules as and when they themselves decide and they are ready. It looks here that Boost has decided on skipping the intermediate stage and going straight to submodules. That sounds awfully fraught: it also demands a lot from those library maintainers not familiar with Git. Submodules are extremely different to SVN externals - they're a very light link, and in many occasions Git does not auto-update submodules even when you tell it (i.e. it'll fetch, but silently not checkout head if it thinks you might lose data). Also, how is Boost going to manage dependency breakage across multiple submodules? Are you planning to keep headers in one monolithic repo but keep anything resulting in a DLL/SO in a submodule? Or are you planning to break out the headers into submodules too? I can see it becoming quite easy for submodules or branches or forks thereof to get out of step with one another. I can see the present submodule heavy approach introducing a lot of anti-Git workflow because those submodules inside the boostorg organization are treated as special compared to other submodules. I'm confused. Sorry. I'm probably not making any sense. Is there a design rationale document somewhere? I can't see one up to date on Google. Niall --- Opinions expressed here are my own and do not necessarily represent those of BlackBerry Inc.

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Re: [boost] Live read-only GIT mirrors of Boost trunk SVN
by Niall Douglas 07 May '13

07 May '13

> > All branches and tags, as far as I can tell, are mirrored correctly. I've > > set a cron job every 24 hours. Theoretically if we had an authors mapping > > file it would work in the opposite direction too i.e. be read-write. > > Nice. You can find a complete author mapping here: > https://github.com/ryppl/Boost2Git/blob/master/authors.txt Arse. I only rebuilt the mirror this weekend because it wasn't mirroring tags/release/* which has obvious value. Fixed now. > > My next task is to live mirror a github repo into Boost Sandbox. Currently > > SubGit segfaults on this due to the complex SVN properties auto-translation > > which requires a specially marked up .gitattributes, but the author is very > > keen to fix the problem. In theory then it ought to just work. > > > > Any mistakes in my Boost mirror, or any problems, or even thoughts are > > gratefully received. > > Don't put too much effort into this; Boost SVN->Git modularization is > just about ready for review :-) My experience with SubGit has been very, very good. I would *strongly* recommend it over git2svn. The company which develops it has been very impressive in response rate and going the extra mile to help me figure out problems. BTW Dave with much help from the same company I've figured out the opposite flow: automated Git => Boost SVN. It took a lot of trial and error to work around Boost's MIME type and EOL conventions, but you can see an exact automated mirror of https://github.com/ned14/TripleGit at http://svn.boost.org/svn/boost/sandbox/triplegit/. I had to squash history because of the MIME type problems though :( but from now on it should be live. I think it would be quite easy to set up a live perfect Git mirror of all Boost SVN, do a transition period where SVN is writeable but GIT read only, and then one day the switch is flipped and it goes the other way round. That way anyone dependent on SVN keeps on working, but without write access. Niall --- Opinions expressed here are my own and do not necessarily represent those of BlackBerry Inc.

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[chrono/date] Unit specifiers arithmetic
by Vicente J. Botet Escriba 07 May '13

07 May '13

Hi, Moving from checked dates to unchecked ones by default and forcing to user the Unit specifiers year/month/day in any date constructor (even the unchecked ones) has some ugly consequences. Note that I was able to build an unchecked date as date d(2013,5,6, no_check); Given year y; month m; day d; the following will not compile now as the constructors expects a year but y+1 is an int. date d(y+1, m, d); The user needs to type date d(year(y+1), m, d); Is this what we want to provide to the user or should we add basic arithmetic on these unit specifiers? Best, Vicente

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Re: [boost] [gsoc-2013] Boost.Thread/ThreadPool project
by Niall Douglas 07 May '13

07 May '13

> Le 30/04/13 17:16, Niall Douglas a ?crit : > >> Le 29/04/13 21:35, Niall Douglas a ?crit : > >> Could you explain me what a central asynchronous dispatcher is? > > An asynchronous procedure call implementation. Here's Microsoft's: > > http://msdn.microsoft.com/en- > us/library/windows/desktop/ms681951(v=vs.85).as > > px. Here's QNX's: > http://www.qnx.com/developers/articles/article_870_1.html. > > Boost.ASIO is the same thing for Boost and C++ but implemented by > > application code. It is *not* like asynchronous POSIX signals which are a > > nearly useless subset of APCs. > I don't see the term "central asynchronous dispatcher" used in any of > the links. Could you clarify what it is? I have to admit I'm struggling to see where your block is, but Dave Abrahams often found the same with me, so it must be me. A central asynchronous dispatcher is the loop which sends callbacks/events to be invoked/processed by other execution contexts. Every OS has at least one in the kernel. Most GUI toolkits like Qt have one. Boost has at least one in the form of Boost.ASIO. The central means one execution context does the dispatch. The asynchronous means that callbacks are processed by recipients asynchronous to the dispatcher. And dispatcher, well that dispatches. > >> If not, please could you elaborate what kind of optimizations can be > >> obtained? > > If you have transactional memory in particular, you gain multi-CAS and the > > ability to (un)lock large ranges of CAS locks atomically, and a central > > dispatcher design can create batch lists of threading primitive operations > > and execute the batch at once as a transaction. Without TM, you really need > > the kernel to provide a batch syscall for threading primitives to see large > > performance gains. > I'm really lost. Multi-word Compare-And-Swap (MCAS) is one of the biggest gains from Transactional Memory. Indeed WG21 has SG5 dedicated to integrating TM into C++17. Some models of Intel's Haswell come with hardware TM assist. I'd take a reasonable guess that MCAS will benefit centralized kernel-based threading primitives architectures such as Windows NT more than decentralized threading primitive architectures such as POSIX. That said, I could see Linux using TM for batch multi-kernel-futex ops, though I'd have to say implementing that without breakage would be daunting. Either way, a central asynchronous dispatcher has information a decentralized implementation does not. That opens more scope for optimization. > > Boost.ASIO's core is boost::asio::io_service. That is its dispatcher > > implementation which each dispatch execution context being executed via > > boost::asio::io_service::run() which is effectively an event loop. Third > > parties then enqueue items to be dispatched using > > boost::asio::io_service::post(). You don't have to run Boost.ASIO using > > multiple threads: it can be single threaded. > > I could not comment until I understand what Boost.ASIO provides and it > can interact with thread_pools :( Boost.ASIO provides a per-thread capable event loop implementation. That automatically makes it an example of a thread pool manager. You may find N3562 Executors and schedulers coproposed March 2013 for Bristol by Google and Microsoft of use to you in understanding the relation between thread pools and Boost.ASIO (http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2013/n3562.pdf) My proposed Boost.AFIO library is an implementation of that same N3562 idea, albeit I extend Boost.ASIO which is IMHO more C++-y whereas Google and Microsoft have gone with proprietary implementations. Also, they include timing and many other more general purpose features, and mine does not (currently) as it's mainly aimed at maximising input/ouput with highly jittery random latency storage. Niall --- Opinions expressed here are my own and do not necessarily represent those of BlackBerry Inc.

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[heap] van Emde Boas tree
by Jeremy Murphy 07 May '13

07 May '13

Should I contact Tim Blechmann directly about the idea of adding a van Emde Boas tree to Boost.Heap, or is proposing it here the appropriate way to go about it? Thanks, cheers. Jeremy

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[any] Divergence between Boost.Any and standard library proposal
by Beman Dawes 07 May '13

07 May '13

A fresh draft of the proposal is up at http://beman.github.com/dot16/any-proposal.html In testing new any_cast examples, Boost.Any is handling one case differently from the proposal: any x; ... x = "Meow"; // x holds const char* This works fine with the Adobe implementation, but with the Boost implementation g++ 4.7.0 -std=c++11 reports: In file included from any_cast_test.cpp:5:0: c:\boost\trunk/boost/any.hpp: In instantiation of 'boost::any::holder<ValueType>::holder(c onst ValueType&) [with ValueType = char [5]]': c:\boost\trunk/boost/any.hpp:52:49: required from 'boost::any::any(const ValueType&) [wi th ValueType = char [5]]' c:\boost\trunk/boost/any.hpp:124:13: required from 'boost::any& boost::any::operator=(Va lueType&&) [with ValueType = const char (&)[5]; boost::any = boost::any]' any_cast_test.cpp:79:7: required from here c:\boost\trunk/boost/any.hpp:169:27: error: array used as initializer VC++ 2012 gets the same error, albeit with a much longer set of messages. AFAICS, the Adobe (and the proposed standard) behavior is preferred. The type does need to decay. Comments? --Beman

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[chrono/date] date conversion and arithmetic with unvalidated dates
by Vicente J. Botet Escriba 07 May '13

07 May '13

Hi, Note that N3344 suggest only day arithmetic for a day representation (which is always valid) and suggest only only a date representation. Could we apply arithmetic operations on a unvalidated date (without striving on UB)? e.g. day arithmetic on a ymd_date ymd_date d1(year(2013), may, day(66)); ymd_date d2 = d1 + day(1); If defined, which must be the value of d2? Could we convert a date representation to another one if the source date is unvalidated (without striving on UB)? e.g. ymd_date -> days_date ymd_date d1(year(2013), may, day(66)); days_date d2 = d1; If defined, which must be the value of d2? Best, Vicente

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[chrono/date] validated versus valid dates
by Vicente J. Botet Escriba 07 May '13

07 May '13

Hi, Allowing to build dates that are not validated doesn't mean that they are not valid. A validated date is always valid. E.g date d(year(2013), may, day(5)); d is not a validated date but is valid. Having a is_validated() function in addition to is_valid() could have its uses assert( ! d.is_validated() && d.is_valid() ); is_validated() function forces to use a bit to store this information on the date representation, but it improves the performances of the is_valid() function. Moving from a possible unvalidated to a validated one would need date d1; ... date d2(d1.year(), d1.month(), d1.day(), check); Instead of this a validate factory makes this clearer date d1; ... date d2 = validate(d1); date validate(date const& dt) { if (dt.is_validated()) return *this; else if (dt.is_valid()) { date res(dt); res.set_validated_(); // this is private return res; } throw bad_date(); } Best, Vicente

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Am I missing something or is Boost: String dictionary?
by david.hagood＠gmail.com 06 May '13

06 May '13

One of the libraries I work with (libXML2) has a very useful concept called a string dictionary, and I am surprised this doesn't appear to be in either STL or Boost. Am I missing something, or is Boost missing something? The basic idea is: Given you have a string and an instance of a dictionary, you can: 1) check if the string is already in the dictionary. 2) Add the string to the dictionary and return the dictionary entry (if the string is already present, return existing entry). The dictionary entries contain a copy of the string. Entries may be compared for equality/inequality in O(1) time. The lifespan of the strings in the entry is managed by the entry. This really simplifies writing parsers and the like, and is such a useful concept that I'm really surprised not to see it in STL or Boost.

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[GitHelp]github.com/boostorg/sandbox comment confusing
by Larry Evans 06 May '13

06 May '13

At: https://github.com/boostorg/sandbox there's a comment by Beman from 10 yrs ago saying: Removed as obsolete - use Boost.Random instead which makes no sense to me. Also, are any of the sandbox files from svn going to be moved to this github sandbox? TIA. -regards, Larry

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Fwd: GSOC:2013 Multiprecision Proposal Review
by Siddharth Jain 06 May '13

06 May '13

Please have a look at my proposal. The link to my proposal is http://www.google-melange.com/gsoc/proposal/review/google/gsoc2013/siddhart… and I have worked a lot on this proposal. Please suggest any changes which could be incorporated to improve this project. Regards Siddharth Jain

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Re: [boost] [gsoc-2013] Boost.Thread/ThreadPool project
by Niall Douglas 06 May '13

06 May '13

> Le 02/05/13 18:01, Niall Douglas a ?crit : > >> That's orthogonal. Boost.Asio provides the funding blocks. A nicer > >> interface that doesn't require an explicit continuation passing style > >> transformation can be built with Boost.Context or a similar library. > >> But it probably needs a future implementation that integrates with > >> ASIO, which is one of the point of Niall Douglas. > > Spot on. Especially as parts of ASIO are due to enter with TR2. I worry that > > a thread pool designed without ASIO in mind would become an orphan isolate. > What a ThreadPool must provide to satisfy the ASIO requirements? That's a very good question. And for me to answer in specifics I'd need to think deeply about the issue, and study examples, neither of which time currently allows given C++Now is just around the corner. All I can say right now - and I agree this isn't very helpful - is make it compatible with opaque third party event loop dispatchers such as Qt's QCoreApplication and QRunnable. Because Qt's implementation details iare opaque to external code, if you can meet compatibility with that you'll probably be compatible with anything Boost.ASIO can come up with, especially as most of Boost.ASIO is header defined. I appreciate that isn't very helpful. Thread pool design is hard :( Niall

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[config/multiprecision/units/general] Do we have a policy for user-defined-literals?
by John Maddock 06 May '13

06 May '13

Folks, I've been experimenting with the new C++11 feature "user-defined-literals", and they're pretty impressive ;-) So far I've been able to write code such as: auto i = 0x1234567890abcdef1234567890abcdef_cppi; and generate value i as a signed 128-bit integer. It's particulary remarkable because: * It actually works ;-) * The value is generated as a constexpr - all evaluation and initialization of the multiprecision integer is done at compile time. * The actual meta-code is remarkably short and concise once you've figured out how on earth to get started! Note however my code is limited to hexadecimal constants, because it can't do compile time radix conversion - that would require a huge meta-program for each constant :-( This is obviously useful to the multiprecision library, and I'm sure for Units as well, but that leaves a couple of questions: 1) We have no config macro for this new feature (I've only tested with GCC, and suspect Clang is the only other compiler with support at present). What should it be called? Would everyone be happy with BOOST_NO_CXX11_USER_DEFINED_LITERALS ? 2) How should libraries handle these user defined suffixes? The essencial problem is that they have to be in current scope at point of use, you can never explicitly qualify them. So I suggest we use: namespace boost{ namespace mylib{ namespace literals{ mytype operator "" _mysuffix(args...); }}} Then users can import the whole namespace easily into current scope right at point of use: int main() { using namespace boost::mylib::literals; boost::mylib::mytype t = 1234_mysuffix; } 3) How should the suffixes be named? There is an obvious possibility for clashes here - for example the units lib would probably want to use _s for seconds, but no doubt other users might use it for strings and such like. We could insist that all such names added to a boost lib are suitably mangled, so "_bu_s" for boost.units.seconds, but I'm not convinced by that. Seems to make the feature much less useful? Many thanks in advance for your thoughts, John.

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[chrono/date] Performance goals and design summary
by Vicente J. Botet Escriba 05 May '13

05 May '13

Hi, After the discussion on other threads I would like to summarize some of my performances goals while refactoring the H.H chrono/date library, just to see if I was wrong and going on the bad direction: 1. *Be able to build dates without validating them.* 2. *I wanted the library to be as efficient as possible when the user uses constant objects or literals, no need to validate at runtime what has already been validated by the compiler*. 3. *Possibility to reassign a date if the parameters represent a valid date.* 4. *No a single date class is better than the others on all the algorithms*. 5. *No additional meta-data in absolute dates so that you don't pay for the relative dates overhead when using absolute dates.* 6. *The user must be able to get all the date related informations at once.* Do you have other? The way I have managed with these goals is 1. *P*rovide an unchecked date construction interface with a no_check_t parameter and an is_valid() function. 2. *T*he date parts day/month/year need to be validated or constructed with no_check_t. 3. dt.set_if_valid(year, month, day) 4. Define the Date requirements all the dates must satisfy, implement ymd_date, days_date, ... 5. Separate the absolute and the relative Date requirements into two Date concepts AbsoluteDate and RelativeDate. Provide at least a relative_date class based on the ymd representation. 6. Conversion between different concrete date classe. H.H approach respond to these goals in a different way 1. date and its parts provide constructors that are not validated, the validation is provided by factories as operator/. 2. I don't think this can be achieved when the date must be validated. 3. No problem, this could be added to H.H approach (at least for its YMD date). 4. Same approach. H.H proposes two classes chrono::day_point (only unchecked) and YMD date. 5. I'm not sure the date YMD class doesn't include meta data (Howard could you clarify your point here) 6. same approach. I have some questions for followed by my personal answer; * *Do you see some unnecessary goals, in particular, is the goal 2**necessary?* IMO, yes. Not providing an interface that allows compiler optimizations is against the C++ philosophy. The question is as always, what would be the gain? In the best case we could avoid 6 comparisons. * *Does the introduction of no_check to achieve goal 1 and 2 results in a uglier date interface?* IMO, yes, but I don't know how to achieve goal 2 without. * *Should a concrete date class provide just the functionalities it is able to do efficiently?* IMO, yes. This would prevent the user of non efficient services (Note that my current design doesn't follows this) * *Do we need a Date concept that a concrete date must model**?* IMO, yes. SO we need two levels, level one provides the most efficient service, level two provides an homogeneous interface. * *Do we need to make the separation between absolute and relative dates?* IMO, yes. While relative dates are powerful they incur on unwanted overhead when absolute dates are needed. Best, Vicente

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[build] Conditional sources and compiler options
by Andrey Semashev 05 May '13

05 May '13

Hi, I'm trying to add some SIMD support to my library and I'm having problems with setting up my Jamfile properly. Basically, I have a number of source files that only need to be compiled when the compiler is of a specific version or later (say, gcc >= 4.7 or msvc >= 12 or intel >= X.Y on x86 but not for other compilers/architectures and not for older versions of the mentioned compilers). Next, I need to add special compiler options (specific for each compiler) just for these files. Natuarlly, I also have other source files that need not these tricks and should be compiled normally, without any special options. All source files have to be compiled into a single library (static or dynamic). Is there any way to do it in Boost.Build? I've read about alternatives in the docs, but they require duplicating the library target, which I'd like to avoid. I also read about conditional requirements, but as I understand they don't allow to specify version conditions (like <toolset>gcc >= 4.7). Also I didn't find any way to specify special build options for particular files. Thanks in advance.

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[boost.preprocessor.iteration] relative file iteration not supported
by Adrian H 05 May '13

05 May '13

Hello, I have used Boost in the past and do like the use of the preprocessor as a way of making repetitious code. However, I found that in a project that I was working on, I needed the ability to iterate over a file relative to the file I was iterating from, and that file wasn't relative to any of the include directories. I thought about this and it makes sense to why it didn't work, but I can see that it can prove to be inconvenient sometimes when someone wishes to make library header files relative to each other to allow for flexible positioning of the related files in the source tree or not have to add new items to the include directory set. I have written a preprocessor library to fill this need, but was wondering if such a library would be of interest to the Boost community. I deliberately tweaked it to be similar to the Boost Preprocessor Iterator library, and can be acquired at https://sourceforge.net/projects/relativeiterate/, including documentation and an example located in the README.txt file. I would appreciate any feedback you may have on this and would be more than willing to make changes to accommodate what would be needed for it to be included into the Boost set. Thank you for your time. Adrian -- ======================================== Adrian Hawryluk BSc. Computer Science ---------------------------------------- Specialising in: OOD Methodologies in UML OOP Methodologies in C, C++ and more RT Embedded Programming GUI Development ========================================

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[chrono/date] constructor, factories and validation
by Vicente J. Botet Escriba 05 May '13

05 May '13

Hi all, Two approaches to checking date validation have been proposed Howard approach: * date constructors build unchecked dates (provide the same order of parameters that the date factories. * date factories (expression using operator/()) build checked dates. * could be completed with make_date that will build checked dates. Advantages: * avoids the ugly no_check (that could be replaced by no_throw) Drawbacks * The 3 sets of date constructor factories must provide all the same order of parameters. * Creating a new factory will mean creating a new constructor on each concrete date class. * The factories must be friend of the concrete dates. My original approach complemented with make_date factory: * constructors without no_check build checked dates, and with no_check parameter build well unchecked ones. Provides only decreasing lexicographic order of arguments e.g. date(year,month,day), date(year,month,day,no_check_t). * make_date provides the usual combinations as provided by factory using operator/() and no_check. * date factories (expression using operator/()) build checked dates Advantages: * There are less date constructors. * We can add as many factories as we are able to construct with checking or not. Drawbacks * the no_throw/no_check/unchecked parameter is ugly and a source of conflict. Alternative approach (reverse the defaults): * constructors without check build unchecked dates, and with check parameter build well checked ones. Provides only decreasing lexicographic order of arguments e.g. date(year,month,day), date(year,month,day,check_t). * make_date provides the usual combinations as provided by factory using operator/() and check. * a make_checked_date could have also a sens. * date factories (expression using operator/()) build checked dates Best, Vicente

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[operators] The Dangling Reference Polarization
by Daniel Frey 05 May '13

05 May '13

I see some good discussion going on, thanks to everyone participating! Rest assured that I value both side's contributions, it is important for me (and those agreeing with my perspective) to be able to defend this position and also to keep looking for improvements. If our side can not be defended, it's probably not good enough :) That said, here's what I hope can serve as a first summary, let's first look at it from a technical perspective: If an operator returns an rvalue reference (T&&), it is safe for all use-cases except binding the result to an rvalue- or const-lvalue-reference: T r = a + b + c; // no problem const T r = a + b + c; // no problem T& r = a + b + c; // compile-time error const T& r = a + b + c; // problem (P1) T&& r = a + b + c; // problem (P2) It seems that this is consistent behavior across at least GCC, Clang and VC++. If a compiler shows a different behavior, its likely a compiler-bug. Technically, there is no doubt that the above is a bug, but that doesn't answer the question of whether this is a bug of the user who wrote the above code or if it's a bug of the operator to return an rvalue reference instead of an rvalue. This is where we leave the technical-aspects-land and enter the minefield of opinions, expectations and decisions. I am of the opinion that the above problematic use-cases are a bug on the users side, my line-of-thoughts and my arguments are: a) The above code is explicit, you can spot it in the users code. It's not something that happens silently. b) The above code always looked suspicious to me anyways, it has a code-smell that I just don't like. c) It rely's on the fact that it extends the lifetime of a returned temporary value. The rules of the C++ standard that allow this are quite clear, and hence it's the users responsibility to make sure that there actually is a temporary value whose lifetime can be extended. It has always been an error if the expression returned a reference and not a value. Consider const std::string& oops = std::vector<std::string>(1, "hello, world" ).front(); This compiles are creates a dangling reference, as the standard says that front() returns a reference and not a value. It's not 100% comparable as in this case the standard guarantees a bug, but the main point for C++ has always been which guarantees are given and not about a certain expectation one might have. As an example: static_assert( std::is_empty< std::tuple<> >::value, "Expectation 1 broken" ); static_assert( std::is_empty< std::array< T, 0 > >::value, "Expectation 2 broken" ); // with any valid T The first case is certainly a reasonable expectation and it currently works for all implementations of std::tuple that I know of, but it is not guaranteed! If your code relies on it and it breaks in the future, you can not blame the person who modified std::tuple. The second case is also a reasonable expectation, but it breaks everywhere and AFAIK there is no standard-conforming way to implement std::array so that std::array<T,0> is empty. For the curious, here's the StackOverflow question I asked about it: <http://stackoverflow.com/q/15512827/2073257>. Another example about how to properly handle expectations vs. guarantees: <http://stackoverflow.com/q/14882588/2073257>. d) I fail to see any valid use-case for binding the result of the expression to a reference. Can someone please provide a convincing example of why (P1) or (P2) are needed/useful? Keep in mind that in the context of operator+ (or any other operator in question), we already require that the type T is copy-/moveable and that copy-elision most likely takes place if you use "T r = …" instead of "const T& r = …". e) The alternative needs to prove its claimed/theoretical efficiency in practice. Too often I have heard about "sufficiently smart compilers", but I'm more the prove-it-in-the-real-world type. So summarizing it once again: For a) and b), this is just an observation and my personal opinion. c) means it's important to talk about guarantees, not just about expectations (no matter how reasonable they are). d) poses the question if we loose something if we don't guarantee that (P1) and (P2) are allowed. I currently have several ideas/option of how we could improve Boost.Operators, some of which I already mentioned, some which only recently occurred to me. Before I will discuss these, I'd like to resolve (if possible) the Dangling Reference Polarization and gather more opinions/feedback. So far, I found the discussion both challenging and very helpful, again thanks to everyone participating! Best regards, Daniel

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[gsoc] Boost.Multiprecision Proposal
by Saurav 04 May '13

04 May '13

Hi, I have attached my proposal for the Boost.Multiprecision project. It has been provided in PDF format for better readability. Please have a look and give your feedback. Best regards, Saurav

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[Boost.ThreadPool] GSOC 2013 Proposal
by Ian Forbes 04 May '13

04 May '13

Hi, I am submitting my Google Summer of Code proposal for review. My proposal is for the Boost.ThreadPool library. It will be based on work done here: https://svn.boost.org/trac/boost/wiki/SoC2013#Boost.ThreadThreadPool The current proposal can be found at: http://cs.mcgill.ca/~iforbe/gsoc2013.html The original proposal can be found here: http://www.google-melange.com/gsoc/proposal/review/google/gsoc2013/en4bz/1 , although it has broken HTML tags and is ill formatted. Thanks goes to Vicente J. Botet Escriba for pointing out that Boost does in fact has LockFree concurrent data structures. Please feel free to respond with any questions or criticism. I will try to respond to the best of my ability. Thanks, Ian Forbes

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[chrono/date] year/day/week literals
by Vicente J. Botet Escriba 04 May '13

04 May '13

Hi, on the GSoC discussion about Boost.Chrono/Date proposal we were discussing about date construction. Some of us think that we need to use named types for day, month, year and week so that the date constructors are not ambiguous. Everyone agree with the constant object for month. date dt(year(2013), may, day(3)); But having to use day(3) or year(2013) seems to wordy. I was wondering if we can not add some literals for day, year and week so that we can just write date dt(2013y, may, 3d); The advantage I see in addition to been less wordy, is that we will have a compile error when the year, day or week is out of range. What do you think? Vicente

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Live read-only GIT mirrors of Boost trunk SVN
by Niall Douglas 04 May '13

04 May '13

The live GIT mirrors of Boost trunk SVN have become a bit stale in recent months: https://github.com/ryppl/boost-svn, long time favourite of many, now 4 months stale. https://github.com/Beman/boost-trunk-git-svn is now 2 months stale. https://github.com/alexanderkjeldaas/boost-mirror is fresh, but has no branches nor tags. They all generally use git-svn, which tends to be brittle and not translate commits perfectly unfortunately e.g. SVN eol properties and other such metadata. So I decided to try out a new Subversion <=> Git mirroring tool, SubGit v2.0 EAP (http://subgit.com/eap/) whose author very kindly gave me a free open source licence and the result is at: https://github.com/ned14/boost-trunk All branches and tags, as far as I can tell, are mirrored correctly. I've set a cron job every 24 hours. Theoretically if we had an authors mapping file it would work in the opposite direction too i.e. be read-write. My next task is to live mirror a github repo into Boost Sandbox. Currently SubGit segfaults on this due to the complex SVN properties auto-translation which requires a specially marked up .gitattributes, but the author is very keen to fix the problem. In theory then it ought to just work. Any mistakes in my Boost mirror, or any problems, or even thoughts are gratefully received. Niall

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Specific-Width Floating-Point Typedefs
by Paul A. Bristow 04 May '13

04 May '13

There has recently been some discussion on improving portability of programs using floating-point. Drawing on the benefits from definition of typedefs for int32_t, int64_t, int128_t . we have drawn up a proposal to add similar typedefs for floating-point. Our draft document (in both html and pdf) is at https://svn.boost.org/svn/boost/sandbox/precision/libs/precision/doc/html/i… https://svn.boost.org/svn/boost/sandbox/precision/libs/precision/doc/precis… We hope to propose this to the SG6 Numerics subgroup of WG21 ISO C++ standards body. But would welcome comments from Boosters to help us improve this proposal. Thank you. Paul --- Paul A. Bristow, Prizet Farmhouse, Kendal LA8 8AB UK +44 1539 561830 07714330204 pbristow(a)hetp.u-net.com

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date libary construction
by Shamsher Siddiqui 04 May '13

04 May '13

i am deeply regretting for not responding your Question and for not posting the google summer of code Proposal . my pre semester exams are going on so i was busy in preparing which is ending on 7 may which is coming tuesday so i will be always not active during this period but i will try to respond to discussion which happening on the mailing list . i am finally sending only the proposal part . Proposal for DATE LIBRARY 1)Construction of Date: According to paper [2] there were many benchmark set but date should be represented in both ways i.e field and serial .Field and serial representation have their advantage over each other under certain operation . No invalid dates can be entered considering range cheaking ,non existent date if entered bad_date exception is thrown during the time of constructing the date. Constructing constant object for day,week_day. Date construction concrete structure <template class date_concrete> class date_pre { //year, month,week day //constructors //basic accessors declaration //conversion accessors //airthematic operation //camparison operator for date camparison } 2) Arithematic Operation On date Date airthematic can be done on three units i.e day,month,year.In chrono date ::calendar(Gregorian calendar) length of month and year is not fixed : day arithematic Adding number of days to date until range doesn’t exceed Implementing last day arithmetic to avoid the bad date excepti Eg. aug/last/2011 +months(1)= sep/30/2011 aug/31/2000 +months(1)=sep/31/2000 //invalid date bad date excep thrown month arithmetic Month arithmetic is quite complex compared to day arithmetic since number of are not fixed . (month day <=28 || month day =last day ) always add month month day =29 cheak for leap year and than add month Month day>=30 add but don’t add if resulting month is feb Using constant objects for month arithmetic. year arithematic Always add year to date considering the condition of leap year Reversal of date back to original date Usage of last day during year arithematic 3) InterConversion field representation & serial representation Some operation are quite fast on field but airthematic operation are much faster on serial campared field representation .So it is necessary to provide the inter-coversion so that it can be easily converted from one representation to another. Constructing bi-directional conversion of serial and field by making use of memoization optimization techinique. 4)Gregorian calendar implementation This Gregorian calendar will be a hybrid calendar that support both Julian and Gregorian calendar with a single discontinuity(the day on which Gregorian calendar was adopted ).The only difference between gregorian and julian is leap year calculation and before day of adoption of Gregorian calendar ,Julian calendar is implemented in this date library. The concrete draft for implementation for calendar template< typename ymd_type ,type name date _int _type > class gregorian_calendar { public : typedef ymd_type ymd _ type ; typedef typename ymd_type : : month_type month_ type ; typedef typename ymd_type : :day_type day_type ; typedef typename ymd_type : : year_type year_type ; typedef date_ int _type date_int_type ; static unsigned short day_of_week (const ymd _type &ymd ) ; static int week_number (const ymd_type &ymd ) ; static date_int_type day_number(const ymd_type &ymd ) ; static ymd_type from_day_number(date_int_type) ; static date_int_type julian_day_number(const ymd_type &ymd) ; static bool is_leap_year(year_type) ; static unsigned short end_of _month_day( year_type y ,month_type m ) ; static ymd _ type epoch() ; static unsigned short days _ i n _week(); }; 5)Building date iterator ,date output and date input Date Iterator will generate the date based on initial condition and end.Bidirectional iterator will do all the generation of series of date.Various iterators which will be implemented are day ,week ,month ,year Iterator. date output same as H. Hinnant. Questions: 1)could you explain us why do you think a class template date is a good alternative? i am using the template class since it will implement the user extensibility .This is very important feature for developer but not for normal user because developer likes to customise code it will give them to add or modify without removing features. 2) What is the expected service of the concrete classes? Which concrete representations would you provide? i have made the concrete class to show some of details of the date library which i am going to implement . <template date_concrete> class date_pre { /*year, month,week day construction of date_field i.e serial and field based reprasentation*/ /*details of constructor 1)date_pre(); //default constructor to initialise the date with the initial default value set 2)date_pre(year_type year,month_type month,day_type day); /*this constructor will initialize the date with values given by the user . but the constructor argument arrangement can be differ according to user or the country date format used */ 3)date_pre(year_type year,month_type month,week_of_month_type week_number,weekday_type wd); //this will constructs the date like monday in week 20 of 2013 4)date_pre(special day sp); //this will day construct the date with the special values like mothers day ,christmas in year //basic accessors declaration //conversion accessors //airthematic operation //camparison operator for date camparison //Coversion of calendar }; these all same as in H. Hinnant proposal except the conversion of Julian calendar to gregorian calendar . 3) How would you implement the memoizer for conversions? Would it be thread safe? Could you post an example how your date_pre and gregorian claendar classes are used? in summary, how your proposal improc-ves H.H implementation or my prototype? since pre semester are going so can i answer to this 2 question after coming tuesday ie 7 may 2013 sorry again for not answering ur questions i will try to be active on the mailing list during my pre semester xam Thanking You Shamsher Ahmed

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