January 2011 - Boost - lists.boost.org

Re: [boost] [string] Realistic API proposal
by Ivan Le Lann 29 Jan '11

29 Jan '11

----- "Artyom" <artyomtnk(a)yahoo.com> wrote : > Hello All, > > I'd like to provide a realistic string API proposal: Thanks for your contribution. I do have a naïve question: What happens to your extensions when "Char" template argument is not char? Do they still have a meaning ? Ivan

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Re: [boost] [string] proposal
by Joe Mucchiello 28 Jan '11

28 Jan '11

On Jan 28, 2011, at 12:59 PM, Dean Michael Berris wrote: > > And I stopped before I write too much -- the initial version is > already up: >https://github.com/downloads/mikhailberis/cpp-string-theory/cpp-string-theo… > > > -- I'll give it more information and the actual interfaces and > implementation as soon as I get some Z's. :) > Hi, I have a question. You keep saying that the string (or chain) has no encoding the string is "just a sequence of bytes" but that doesn't make sense. The bytes have to have some form of encoding otherwise how do the adapter classes know how to convert the sequence of bytes into an encoded sequence? When you say the string has no encoding do you simply mean the default encoding is implementation dependent? Did I miss where you said this somewhere? Oh, and I see the value in an immutable string. I just think you are still at such a high level that it's hard to see where you are going for some people. Joe

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Re: [boost] [Boost-users] Git vs SVN (was: Re: What's happened to Ryppl?)
by Dave Abrahams 28 Jan '11

28 Jan '11

[moved to developers' list] On Fri, Jan 28, 2011 at 8:48 AM, Vladimir Prus <vladimir(a)codesourcery.com> wrote: > May I suggest that to keep signal/noise ratio on the list to acceptable > level, we don't have a general VC shootout discussion. It will never lead > to anything. +1, but I don't think anyone intended to do that. > Rather, the parties interested in having Boost switch to any > version control system that is not SVN should propose a specific plan, > including hosting, administration, adjustment of all scripts, new workflows > for Boost maintainers and authors of proposed libraries, etc? > > If would be seriously not funny if 1000 messages later we'll find that > git is about to solve every problem on earth, but there's nobody to > do *complete* transition and onging maintenance. I think what you've just said is an important part of the discussion we should be having right here and now. -- Dave Abrahams BoostPro Computing http://www.boostpro.com

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[mpl] Using transform problem and solution
by Edward Diener 28 Jan '11

28 Jan '11

I have a boost::mpl::vector of nullary metafunctions and I need to transform it into a sequence of the metafunction's inner types. As in: typedef boost::mpl::vector<boost::mpl::identity<int> > tvec; typedef boost::mpl::vector<int> tvecinner; So I try boost::mpl::transform: typedef typename boost::mpl::transform<tvec,_1>::type ttrans; BOOST_MPL_ASSERT((boost::mpl::equal<tvecinner,ttrans>)); But that does not work and the assert fails. Evidently my _1 is not working by itself although it seems as if it should because it is a placeholder expression and its inner type is what I want. So I try: template <class T> struct tself : T { }; and now instead: typedef typename boost::mpl::transform<tvec,tself<_1> >::type ttrans; BOOST_MPL_ASSERT((boost::mpl::equal<tvecinner,ttrans>)); works fine and the assert succeeds. But that 'tself' hack seems like it should be really unnecessary. Have I missed something cleaner and easier ?

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Trac down?
by Beman Dawes 28 Jan '11

28 Jan '11

I'm getting a blank page when I try to access svn.boost.org/trac/boost/ That's a serious impediment to building the 1.46.0 beta. I really need the release manager's checklist from the trac. Are others able to access Trac? --Beman PS: The good news is that SVN seems to be running really well, with none of the slowness and server errors that were a problem several weeks ago.

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[Boost.Algorithm] Proposal for addition of a new algorithm: ThreeWayMerge
by Aleric Inglewood 28 Jan '11

28 Jan '11

Greetings everyone. I don't think that Boost.Algorithm exists: I only saw it refered to on mailinglists. I looked at the existing libraries, but I'm not sure where this would fit in. I'd like to propose the addition of a new algorithm, very much like std::set_union and companions, that I came up with recently. This algorithm does a three-way merge of containers. Comparing it to std::set_union, which needs five iterators to be passed, and a compare functor (two iterators for the range of input 1, two iterators for the range of input 2 and one output iterator), the three_way_merge algorithm takes three iterator ranges and one output iterator, so it takes seven iterators. The algorithm also takes two functors: a compare and an is_equal. The former should be the ordering Predicate used with the containers (they must be ordered containers, like std::set or set::map), while the is_equal functor is usd to compare the "payload" of the data (which is not part of the sorting key). The algorithm applies trivial merge rules in all cases where the merge is trivial, and calls a third functor to perform the three-way merge of the payload in those cases that a three-way merge is not trivial. In it's current form, my algorithm looks as follows: https://github.com/AlericInglewood/contribmerge/blob/master/src/three_way_m… I used it (in that project) to three-way-merge a file with a specific format: a list of contributors, each with a list of contributions. The algorithm is used recursively (which is very neatly showing it's true power, of course). For this usage example, please see https://github.com/AlericInglewood/contribmerge/blob/master/src/contribmerg… Aleric

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Re: [boost] [string] proposal
by Anders Dalvander 28 Jan '11

28 Jan '11

On Thu, 27 Jan 2011 12:51, Nevin Liber <nevin(a)eviloverlord.com> wrote: > I'd like to see this broken up into three discussions: > > 1. Immutable strings. Immutable or not, I don't see a direct use for modification of individual code-units (e.g. char, wchar_t) in a string. Too many things can go wrong. Some kind of manipulation of code-points, yes, but not code-units. Anyway, code-points are not the end either. Multiple code-points may be needed to represent a grapheme, using combining characters. And sometimes a single code-point can represent several graphemes, such as ligatures. > 2. utf8 strings. Although I personally prefer UTF-8 encoded strings, the internal encoding is more or less irrelevant for an implementation based on rope or similar non-contiguous data structure. I believe this is what Dean Michael Berris is suggesting. I think this is especially true if direct access to individual code-units are prevented. For an implementation using a contiguous data structure and providing a constant time c_str member function I'd really want to see some option to set the internal encoding of strings. Performance-wise it may be preferred to use UTF-16 internally when using for example Win32 API, if an extra copy can be avoided. > 3. Unrealistic pipe dream about replacing std::string. Replacing std::string will never happen. Deprecating std::string in favor of std::text/std::unicode/std::xstring may happen in the long run. Regards, Anders Dalvander -- WWFSMD?

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[signals2] -no instance of overloaded function
by Tal Agmon 28 Jan '11

28 Jan '11

Hi All, I get error no instance of overloading ... when using <memory> shared_ptr can anyone explain why? tested on: windows7 vc100 // not working //#include <memory> // fail to compile //using std::tr1::shared_ptr; // works #include <boost/shared_ptr.hpp> // works find using boost::shared_ptr; [code] #include <iostream> #include <boost/signals2/signal.hpp> class Reporter { public: explicit Reporter(const std::string& s) : s_(s) {} void says() const { std::cout<< "news : " << s_ << std::endl; } private: std::string s_; }; class NewsStation{ public: void displayNews(const Reporter& r) const { r.says(); } }; int main() { using namespace boost::signals2; typedef signal<void (const Reporter&) > signal_type; shared_ptr<signal_type> signalPtr(new signal_type); typedef shared_ptr<NewsStation> news_station_ptr; Reporter tal("when using std:tr1::shared_ptr --> no instance of overloaded function, matches the argument list) "); news_station_ptr newsStationPtr(new NewsStation); signal_type sigNews; sigNews.connect( signal_type::slot_type( &NewsStation::displayNews, newsStationPtr.get(), _1).track(newsStationPtr)); sigNews(tal); } [code]

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Re: [boost] [signals2] -no instance of overloaded function
by Ivan Le Lann 28 Jan '11

28 Jan '11

----- "Tal Agmon" <tal.boost(a)gmail.com> wrote : > Hi All, > > > I get error no instance of overloading ... when using <memory> > shared_ptr > can anyone explain why? > > tested on: > windows7 vc100 > > (snip) > sigNews.connect( signal_type::slot_type( > &NewsStation::displayNews, newsStationPtr.get(), > _1).track(newsStationPtr)); > sigNews(tal); > } Just a bet : I suspect the track method exspects a boost::shared_ptr. Or something a boost::shared_ptr can convert to. Ivan.

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[iterator] Unmerged changes
by Daniel James 28 Jan '11

28 Jan '11

Hi, I've been looking through the unmerged changes in the iterator library. I think it should all be merged/fixed/reverted for 1.47. These seem to be the outstanding changes: An old fix from David Abrahams: https://svn.boost.org/svn/boost/changeset/58012 function_input_iterator from Dean Michael Berris: https://svn.boost.org/svn/boost/changeset/62615 https://svn.boost.org/svn/boost/changeset/62710 The result_of changes (partially merged, but will be reverted for 1.46): https://svn.boost.org/svn/boost/changeset/62625 https://svn.boost.org/svn/boost/changeset/68205 Any comments on these? Anyone willing to take charge, or shall I deal with them? Daniel

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