April 2011 - Boost - lists.preview.boost.org

Re: [boost] [Filesystem] Linking problem with 1_46_1
by Max Moorkamp 05 Apr '11

05 Apr '11

> Max Moorkamp wrote: >> > Hi, >> > >> > I have recently upgraded to boost 1_46_1 and since then I am >> > experience linking problems with the filesystem library. >> > >> > I have performed a standard install using ./bootstrap.sh; bjam; bjam >> > install under Ubuntu 10.04 with the default gcc (4.4.3). >> > I can boil the problem down to this test program: >> > >> > #include<boost/filesystem.hpp> >> > #define BOOST_FILESYSTEM_VERSION 3 >> > #define BOOST_FILESYSTEM_NO_DEPRECATED >> > >> > int main() >> > { >> > boost::filesystem::copy_file("a", "b"); >> > } >> > >> > compiling this with >> > >> > g++ test.cpp -lboost_system -lboost_filesystem >> > > It might be as simple as the order you link to the libraries. The boost > filesystem library depends on the boost system library, so you should > probably put "-lboost_system" after "-lboost_filesystem" on the command > line to link your program. That was my first thought, but the linking error does not come from boost_system, plus all of g++ test.cpp -lboost_filesystem -lboost_system g++ test.cpp -lboost_system -lboost_filesystem g++ test.cpp -lboost_filesystem give the same /tmp/cc9OO6P2.o: In function `boost::filesystem3::copy_file(boost::filesystem3::path const&, boost::filesystem3::path const&)': test.cpp:(.text._ZN5boost11filesystem39copy_fileERKNS0_4pathES3_[boost::filesystem3::copy_file(boost::filesystem3::path const&, boost::filesystem3::path const&)]+0x2a): undefined reference to `boost::filesystem3::detail::copy_file(boost::filesystem3::path const&, boost::filesystem3::path const&, boost::filesystem3::copy_option::enum_t, boost::system::error_code*)' collect2: ld returned 1 exit status Regards Max -- Max Moorkamp IFM-GEOMAR Wischhofstr. 1-3 24148 Kiel Tel.: Germany - 431 - 600 2570 FAX.: Germany - 431 - 600 2915

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[lexical cast] Performance improvements
by Antony Polukhin 05 Apr '11

05 Apr '11

Working with Boost Lexical Cast library found that some casts are working really slow. For example, cast from short to int is done via cast from short to char[], and cast from char[] to int. Cast from char* to string is done via string() constructor call and string`s append function call (instead of string constructor call with char array as a parameter). So I wrote patch to Boost Lexical Cast library, that returns Target directly constructed from Source in cases, when: 1) Source and Target are arithmetics (and not char or wchar_t), and all values of Source are in range of Target 2) Source and Target are both char or both wchar_t 3) Source is array of CharT and Target is std::basic_string<CharT, ...> 4) Source and Target are std::basic_string with same template parameters It gives performance boost more than 10 times in case 1) , about 7 times in case 2), and about 1.5 times in cases 3) and 4). Existing tests for Boost Lexical Cast library cover considered cases. Patch was successfully tested on Intel 11.1.072, g++-4.4.5, VC++9 compilers. P.S.: I`m a newbie here, so where shall I send this patch? Shall I test it on other compilers?

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[Filesystem] Linking problem with 1_46_1
by Max Moorkamp 05 Apr '11

05 Apr '11

Hi, I have recently upgraded to boost 1_46_1 and since then I am experience linking problems with the filesystem library. I have performed a standard install using ./bootstrap.sh; bjam; bjam install under Ubuntu 10.04 with the default gcc (4.4.3). I can boil the problem down to this test program: #include <boost/filesystem.hpp> #define BOOST_FILESYSTEM_VERSION 3 #define BOOST_FILESYSTEM_NO_DEPRECATED int main() { boost::filesystem::copy_file("a", "b"); } compiling this with g++ test.cpp -lboost_system -lboost_filesystem results in this error message /tmp/ccBuSw7s.o: In function `boost::filesystem3::copy_file(boost::filesystem3::path const&, boost::filesystem3::path const&)': test.cpp:(.text._ZN5boost11filesystem39copy_fileERKNS0_4pathES3_[boost::filesystem3::copy_file(boost::filesystem3::path const&, boost::filesystem3::path const&)]+0x2a): undefined reference to `boost::filesystem3::detail::copy_file(boost::filesystem3::path const&, boost::filesystem3::path const&, boost::filesystem3::copy_option::enum_t, boost::system::error_code*)' collect2: ld returned 1 exit status I had a look at this thread http://boost.2283326.n4.nabble.com/Filesystem-problems-with-g-std-c-0x-td26… but adding or removing -std=c++0x does not change anything. I also tried to see whether any special compiler options were used during the build of boost, so here is the line for operations.hpp "g++" -ftemplate-depth-128 -O3 -finline-functions -Wno-inline -Wall -pthread -DBOOST_ALL_NO_LIB=1 -DBOOST_SYSTEM_STATIC_LINK=1 -DNDEBUG -I"." -c -o "bin.v2/libs/filesystem/build/gcc-4.4.3/release/link-static/threading-multi/v3/src/operations.o" "libs/filesystem/v3/src/operations.cpp" There is nothing there that strikes me as special, any ideas anyone. Regards Max -- Max Moorkamp IFM-GEOMAR Wischhofstr. 1-3 24148 Kiel Tel.: Germany - 431 - 600 2570 FAX.: Germany - 431 - 600 2915

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[trac] Phoenix Component
by Thomas Heller 04 Apr '11

04 Apr '11

Hi, Can someone please add a Phoenix component to trac and add me and JdG as maintainer? Thanks, Thomas

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[GSoC] coerce (previously construe_cast)
by Jeroen Habraken 04 Apr '11

04 Apr '11

Hi, Some time ago I've announced construe_cast as a library which builds upon boost.spirit to create a cast-like operator aiming to provide an alternative to lexical_cast providing greater speed and flexibility. It has since been renamed to boost.coerce (it's the last rename, I promise) and it has found its way to the boost sandbox where development will continue. For the original email I'd like to point you to http://boost.2283326.n4.nabble.com/construe-cast-call-for-interest-and-feed…. Due to an internship I haven't been able to get much done on this project lately. I would still very much like to see this through and because of this I would like to propose this as a GSoC project. There is quite a bit to be done to get this to the level expected from a potential boost library, however I believe I can get it in a state where it can be reviewed within the timespan set for the GSoC. The request for feedback stands, and please be expecting my proposal! Regards, Jeroen Habraken

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[serialization]Can I pass the grandparent class to BOOST_SERIALIZATION_BASE_OBJECT_NVP?
by Takatoshi Kondo 04 Apr '11

04 Apr '11

Hi, I'd like to check that my approach is correct or not. Condition: There are three classes A, B and C. The class A is the base class of B. The class B is the base class of C. Requirements: 1.The class A and B shouldn't depend on the serialization library. 2.The class C should be serialized via the base class A (Polymorphic). My approach: Applying non intrusive version serialize function to the class A and B. In the class C, using the macro BOOST_SERIALIZATION_BASE_OBJECT_NVP with the argument A (not B). I skip the class B in the class hierarchy on purpose. If I pass it B instead of A, the following exception would be occurred. "unregistered void cast struct C<-struct A" I believe that my approach is correct. (using A) But I suspect that it might work correctly by accident. #include <boost/serialization/serialization.hpp> #include <boost/archive/xml_oarchive.hpp> #include <boost/archive/xml_iarchive.hpp> #include <boost/serialization/nvp.hpp> #include <boost/serialization/export.hpp> #include <fstream> struct A { virtual ~A() {} }; // non intrusive serialize namespace boost { namespace serialization { template<class Archive> void serialize(Archive& /*ar*/, A&, unsigned int const /*version*/) {} }} struct B : public A {}; // non intrusive serialize namespace boost { namespace serialization { template<class Archive> void serialize(Archive& /*ar*/, B&, unsigned int const /*version*/) {} }} struct C : public B { friend class boost::serialization::access; template<class Archive> void serialize(Archive& ar, unsigned int const /*version*/) { ar & BOOST_SERIALIZATION_BASE_OBJECT_NVP(A); // My approach // ar & BOOST_SERIALIZATION_BASE_OBJECT_NVP(B); } }; BOOST_CLASS_EXPORT(C) int main() { { std::ofstream ofs("test.xml"); C c ; A* a(&c); boost::archive::xml_oarchive oa(ofs); oa << boost::serialization::make_nvp("a", a); } { std::ifstream ifs("test.xml"); boost::archive::xml_iarchive ia(ifs); A* a; ia >> boost::serialization::make_nvp("a", a); assert(dynamic_cast<C*>(a)); delete a; } } Regards, Takatoshi Kondo

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[local] files organization
by Vicente Botet 04 Apr '11

04 Apr '11

Hi, While installing Boost.Local I observed that there are 3 directories under Boost to update; detail, local and utility. To make easier the update, it will be worth to move all the detail and utility parts under the local directory. local/ detail/ preprocessor/ keyword/ variadic_macro_data utility/ BTW, if you just copy files from other libraries waiting from them to be released, shouldn't you preserve the copyright (VMD)? Shouldn't the utility identity go to the detail/preprocessor directory? Best, Vicente -- View this message in context: http://boost.2283326.n4.nabble.com/local-files-organization-tp3424684p34246… Sent from the Boost - Dev mailing list archive at Nabble.com.

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Re: [boost] [lexical-cast] version of lexical_cast in 1.46.1 is quite older than in trunk
by Antony Polukhin 04 Apr '11

04 Apr '11

> "SergV"<serge-voropaev(a)yandex.ru> wrote in message > news:loom.20110329T052451-354@post.gmane.org... > We discovered lexical_cast from 1.43 and 1.46.1 versions do not work in > our > program. But version of lexical_cast from trunk work very well. Version > information: > 1.46.1 - rev. 56161 13.09.2009 > trunk - rev.65279 5.09.2010 > > 1) Is there any reason that release does not include last version > lexical_cast > from trunk? > 2) May be there are a lot of such forgotten files in trunk? There is also some mess with tickets for lexical_cast : some tickets are in bug database for months (and even years). > On Wed, 2011-03-30 at 18:16 +0300, Matthew Chambers wrote: >> Does that mean lexical_cast is orphaned? I'd like to see lexical_cast have optimized conversions for >> string->number and number->string (template specializations using strtol/strtod; or optionally using >> the spirit-based construe_cast). Being able to pass ios flags to control the format (i.e. boolalpha) >> would be nice too [...] >> Which reminds me - lexical_cast error messages are not very >> informative[...] > >Agreed. This should be added as well[...] > >-Matt I can take care about some of this issues, but if lexical_cast is orphaned and not maintained any more it`ll be just wasting time. - Antony

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Re: [boost] [MSM] feature request stop(const event& event_)
by Christophe Henry 03 Apr '11

03 Apr '11

Hi Richard, >> While big improvements were made, there will always be a limit, >> especially with VC9. Did you try with VC10? It'd be interesting to know. >I will try this for you when I will have a spare 10 minutes. >I did use for some time VC10 in the past and I did not observe too >much difference in the heap usage during compilation Thanks. I personally didn't notice big improvements either :( >The public start has a limitation that I can't tell during runtime what >event is triggering the start e.g I can't specify the initial event in >runtime for the initial transitions. > >I want to use start to cause the same behavior as an entry transaction >causes on a composite state machine. I just committed a new version into the trunk (70961) where you will find: - a stop() method - like for the initial event, you have the possibility to define your own event by adding a typedef inside the front-end: typedef my_final_event final_event; - a start and stop method with an event as parameter. I'm not sure it's a great idea as you have the typedef but we can give it a try. Please notice that this version calls on_entry so you shouldn't do it yourself. I didn't update the doc yet, I'll do it for 1.47. Regards, Christophe

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[GSoC] Distinct check, hash and block cipher library ?
by Pierre Talbot 03 Apr '11

03 Apr '11

Hello everyone. My name is Pierre Talbot and I'm a Belgian student who'd like to work with the Boost community in the context of GSoC, and if it's possible I hope much more. I'm also (note the "also") interested in the checks and hashes projects. I tried to code an interface of the checks and hashes projects and actually I thought we could split this project into two distinct projects. Actually, the checks and the hashes are different in many ways. Indeed I though we could address them : the check project : - Control redundancy check : CRC 16/32/64 - Checksums : Fletcher, Adler, Luhn, and Verhoeff algorithm - Credit card checks : VISA, Mastercard, AMEX, ... - International number : ISBN, ISSN, EAN, IBAN, ... the hash project : - MD family : MD5, MD6 (optionnal). - SHA-1 and SHA-2 family : SHA-224, SHA-256, SHA-384, SHA-512 - SHA-3 as Black or Groslt,... - Tiger - RIPEMD family (RIPEMD-128, RIPEMD-160, RIPEMD-256) - RadioGatun - Very Smooth Hashing (VSH) - Optionnal(?) : Non cryptographic hash function Why so many different algorithms ? I think the users need a larger range of hashing functions. Some hashes are quicker, lighter or more resistant to collision. Others are better for the micro-controllers, and some systems use other hashes than SHA-1 or MD5. Why split one project into two distinct ones? Because I think that in the GSoC context, these two projects are too much work for a single person to provide a complete documentation. Indeed if you think it's impossible to split it, I think that the hashes should be limited to the SHA-1/2 and MD5 algorithms (because there are the most widespread). Furthermore, the documentation of the hash project should be even more complete if we want to provide details about the speed/ usage of an algorithm. I also want to discuss the possibility of building a Block Cypher Algorithm Library. Firstly I would like "to share a plan of a library" : - The three 128 bits algorithms recognized by ISO : AES (Rijndael), Camellia, and SEED. - Two very powerful algorithms : Blowfish (currently resistant to cryptanalysis) and Twofish (finalist to the AES contest). - Serpent (finalist to the AES contest). - The old DES and Triple-DES algorithms I read about the timing attacks on this kind of algorithms. In the first place, I think we could ignore those attacks because the attackers need to know details about the server configuration (processor, amount of RAM, ...). They also need to know the precise time of each algorithm's instruction in the processor. So this attack needs to be carried out in a "local context" and not on the internet. (Considering that packets have a variable latency). It's for these reasons that I think these attacks are highly theoretical. I think we should improve this library later. What do you think about all of this ? Thank you very much for reading me. Pierre Talbot.

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[config] Purpose of compiler identification macros
by Edward Diener 03 Apr '11

03 Apr '11

In select_compiler_config.h there are a number of compiler identification macros of the form BOOST_CXX_SOMECOMPILER. I can find nowhere in boost where these are being used. What is the purpose of these macros ?

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Re: [boost] GSoC idea - interval trees, ITL tie in
by Brestin Seby 03 Apr '11

03 Apr '11

>> Phil Endecott wrote: >>> Andrew Sutton wrote: >>>>> While reading Boost documentation, and reviews on XInt, I though >>>>> about the possibility of implementing for Boost some new data >>>>> structures that are not yet implemented not even in STL like >>>>> interval trees, binary indexed trees. >>> >>>> These seem like interesting data structures, but I'm not sure that >>>> there's a large demand for them. >>> >>> Brestin, please have a look at the reviews for Joachim Faulhaber's >>> Interval library. Andrew is right that there is not much demand for >>> interval trees. Personally I would still like to have them, though. >> >> Joachim could mentor the GSOC project and the interval tree could >> be an enhancement to his library rather than a new boost library. >> It might be best to reduce the scope to the single data structure. >Hi Sebastian, >interval_tree is still on my todo list for Boost.ICL and didn't make >it to materialize as real code yet. So an implementation would be a >welcome contribution, that is also expected by some boosters ;) I >haven't been active as GSoc mentor yet but it would obviously make >sense. Thank you for your replies. This helps me a lot on writing my proposal. By the way could I add more than one idea to the proposal?

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[testsystem] broken?
by Joachim Faulhaber 03 Apr '11

03 Apr '11

It looks like the tests on boost/trunk and release branch stopped to be updated since Thu, 31 Mar 2011 20:23:30. Is someone able to do anything about it? Regards, Joachim -- Interval Container Library [Boost.Icl] http://www.joachim-faulhaber.de

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GSoC idea - interval trees, binary indexed trees, permutation
by Brestin Seby 02 Apr '11

02 Apr '11

Hello, my name is Sebastian Brestin. I am a student from Romania. While reading Boost documentation, and reviews on XInt, I though about the possibility of implementing for Boost some new data structures that are not yet implemented not even in STL like interval trees, binary indexed trees. I also have an other idea about implementing (Boost:Permutation) a Permutation Class that allows operations on permutations. What do you think?

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Data / String Ref library
by Olaf van der Spek 02 Apr '11

02 Apr '11

Hi, A lot of functions take a const void*, size_t pair as two parameters. This is then cast to a const unsigned char* for further processing. Two parameters means you can't easily pass the result of an expression or function call. One parameter would be handier. const std::string& is also used frequently. However, this forces the caller to use (or construct) std::string, which is undesirable and unnecessary. A solution seems simple: data_ref and string_ref, which represent a pointer pair (void/unsigned char and char respectively). string_ref can replace const std::string&, data_ref can replace const void*, size_t. I think this would be a nice addition to Boost. Is there any interest in a library that solves this problem? -- Olaf

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GSoC XML
by Brestin Seby 02 Apr '11

02 Apr '11

Hello my name is Sebastian Brestin. I am a student from Romania. After another few hours of browsing through Boost's libraries I was thinking: What about implementing DOM into Boost? XML is the most used "data storage mechanism" over the internet. Yet Boost does not have it. I say: Let me code it! Let me now what do you think about it and which of my proposals would bring more utility to Boost.

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Re: [boost] [MSM] feature request stop(const event& event_)
by Christophe Henry 01 Apr '11

01 Apr '11

> Hi Christophe and all > > Now I have to put some effort to residing out code using MSM because > one of our module where we use MSM has reached it's limits and we > won't be able to compile it any more with VC9 32 bit compiler. > In our implementation we have several sub state machines (around 20 > per main state machine instance at the moment) ( nested in 4 level > deep) and over time as we extend the functionality we introduce new > sub state machines which are covering new functionality ... > > We now can not add any more new sub state machines because we can not > compile any more :(. While big improvements were made, there will always be a limit, especially with VC9. Did you try with VC10? It'd be interesting to know. > So I have decided to split the big state machines with a lot of subs > state machines to stand alone small state machine instances and use > our dispatching framework to dispatch events between them. This way I > will get small compile units. Sounds good. > I'm managed to complete a job apart form one problem I have now. > I'm not able to generally trigger the exit functions on the current > active states of a state machine when it is finished it's execution > like when a sub state machine exists to the outer state machine. If you mean in the fsm destructor, it's true. I'd be surprised though if on_exit was not called when leaving a submachine to its outer. > Is it possible to implement something like stop method on the back end > which would call exit on each region current state and than an exit of > the state machine whit an event passed as an argument. ? > > this would help me a lot and it would be similar to the start. Ah yes I remember thinking about it in the early phase of MSM. Unfortunately I don't remember why it was not done, just that I had a reason at that time. Actually I think it'd be even better to automatically call on_exit in the destructor. The start method is there only because you might not want to start a state machine immediately upon creation, but I have never had a very good feeling about it, so I'd prefer not repeating this. Is there a reason why you want a stop method or the calls of on_exit inside the destructor would suffice (provided I don't hit again the issue I mentioned above)? > other minor thing is it possible to make public this version of start > methode in the back_end ? > > template <class Event> > void start(Event const& incomingEvent) I'm not sure you'd be happy with this because on_entry is not called in this version (it's meant to be called from the outer machine, which itself calls on_entry), so you'd have to call it yourself. What are you trying to achieve? Regards, Christophe > > Br. > Richard

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Boost.Serialization issue loading 1.37 binary archive.
by Brandon Kohn 01 Apr '11

01 Apr '11

Hello, I've been using Boost.Serialization for some time, and have found a break while upgrading to 1.46.1 (from 1.37). The problem seems to be the size of the integral type which stores v. 1.37 has: BOOST_ARCHIVE_VERSION(){ return 5; } When saving to the binary_oarchive: // basic_binary_oarchive.hpp void save_override(const class_id_type & t, int){ // upto 32K classes const int_least16_t x = t.t; * this->This() << x; } 1.46.1 has: void load_override(class_id_type & t, int version){ library_version_type lvt = this->get_library_version(); if(boost::archive::library_version_type(7) < lvt){ this->detail_common_iarchive::load_override(t, version); } else if(boost::archive::library_version_type(6) < lvt){ int_least16_t x=0; * this->This() >> x; t = boost::archive::class_id_type(x); } else{ int x=0; * this->This() >> x; t = boost::archive::class_id_type(x); } } The salient point is that on the load in 1.46.1 an int is used to read the value which was stored as int_least16_t in version 5 archives. The trunk seems to have this as well. Regards, Brandon Kohn

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[gsoc] Interest in BGL v2?
by Michael Lopez 01 Apr '11

01 Apr '11

Hello all, My name is Michael and, if there is enough interest from the mailing list, I will be submitting an application for GSoC 2011 to work on the BGL v2. I have been working on a project called Origin ( http://code.google.com/p/origin/) when time permits, that houses the code that I intend to integrate into boost. The project was started by Andrew Sutton and I have taken an active role in its creation. The new library focuses on ease of use, replacement of property maps for labels, data structures with more concise and clear semantics, a new graph concept hierarchy, implementing graph algorithms to align with STL abstractions, and, finally, integrate C++0x into the BGL. I have already worked on the existing BGL back in 2009 for GSoC. While working on the BGL, I started seeing opportunities to bring the BGL more in-line with modern techniques and practices. I found that the library, though robust and quite mature, was lacking in some areas. The most unavoidable being C++0x support. The other design concern was that some of the data structures felt more like meta-programs. This is no good since a meta-program generates types that may model one of many concepts. Another feature that has been on BGL's want list is the implementation of algorithm objects. Some of the algorithm objects are already present in Origin. I realize that this is not a 3 month project. I fully understand that. However, I plan to continue maintaining this library in Origin, as I have been, until it is mature enough for a release and integration into other libraries. Hopefully there is enough interest to get this off of the ground. Please respond with your interests, questions and/or doubts. Michael Lopez

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[lexical-cast] version of lexical_cast in 1.46.1 is quite older than in trunk
by SergV 01 Apr '11

01 Apr '11

We discovered lexical_cast from 1.43 and 1.46.1 versions do not work in our program. But version of lexical_cast from trunk work very well. Version information: 1.46.1 - rev. 56161 13.09.2009 trunk - rev.65279 5.09.2010 1) Is there any reason that release does not include last version lexical_cast from trunk? 2) May be there are a lot of such forgotten files in trunk? Sergey Voropaev

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[MSM] feature request stop(const event& event_)
by Richard Szabo 01 Apr '11

01 Apr '11

Hi Christophe and all Now I have to put some effort to residing out code using MSM because one of our module where we use MSM has reached it's limits and we won't be able to compile it any more with VC9 32 bit compiler. In our implementation we have several sub state machines (around 20 per main state machine instance at the moment) ( nested in 4 level deep) and over time as we extend the functionality we introduce new sub state machines which are covering new functionality ... We now can not add any more new sub state machines because we can not compile any more :(. So I have decided to split the big state machines with a lot of subs state machines to stand alone small state machine instances and use our dispatching framework to dispatch events between them. This way I will get small compile units. I'm managed to complete a job apart form one problem I have now. I'm not able to generally trigger the exit functions on the current active states of a state machine when it is finished it's execution like when a sub state machine exists to the outer state machine. Is it possible to implement something like stop method on the back end which would call exit on each region current state and than an exit of the state machine whit an event passed as an argument. ? this would help me a lot and it would be similar to the start. other minor thing is it possible to make public this version of start methode in the back_end ? template <class Event> void start(Event const& incomingEvent) Br. Richard

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Re: [boost] [submission] STL-compliant containers with copy-on-write
by Alexandr Sterligov 01 Apr '11

01 Apr '11

I'm working with embedded software and we have to use COW containers pretty often. I haven't found any COW container implementation which may replace STL containers and had to implemented it. It is not possible to make STL containers with COW keeping all semantics of the STL containers. For example, almost any member-function may throw, because copy ctor may throw. It is not always safe to replace std::vector with mine cow_vector, but in most cases it is safe. For example, it is not safe if you have saved constant pointer or constant reference from constant cow_vector. But with std::vector saving addresses is not a good idea as well, because resize, push_back and others may cause address change. In my implementation iterators are safe, for example: cow_vector<int> a; a.push_back( 1 ); cow_vector<int> b; b.push_back( 2 ); cow_vector<int>::const_iterator itA = a.begin(); assert( *itA == 1 ); cow_vector<int>::const_iterator itB = b.begin(); assert( *itB == 2 ); b = a; assert( itA == a.begin() ); assert( itB == b.begin() ); assert( *itA == 1 ); assert( *itB == 1 ); a[0] = 3; // or *a.begin() = 3 assert( itA == a.begin() ); assert( itB == b.begin() ); assert( *itA == 3 ); assert( *itB == 1 ); You example: int* p = &v[1]; // copying is done here v[0] = 1; assert( p == &v[1] ); // still valid as copying was done before. But in following case it won't work now: void test( const cow_vector<int>& a ) { const int *a = &v[1]; v[0] = 1; assert( p != &v[1] ); // sorry, another pointer if internal buffer was shared. } Please note, that it's possible to do copying if any reference or pointer is taken from iterator or container itself, but my current implementation doesn't do it. That's easy to change. > IMO it isn't possible to really make that work anyway since STL > containers expose references to their elements *and* make guarantees > about iterator stability and element layout. For example, if v is a > vector and I do > > v[0] = 1; > > it's not allowed to change the address of v[1] > -- > Dave Abrahams > BoostPro Computing > http://www.boostpro.com ---- Best regards, Alexander Sterligov

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GSOC2011 (Introduction)
by Harinderpal Singh 01 Apr '11

01 Apr '11

Hi My name is Harinderpal Singh. I am from Lovely Professional University, Punjab, India. I am a fourth year B.Tech student. I have worked on c++. I also have basic knowledge of Mysql. I have competed in various inter college level competitions. I work on linux(ubuntu) and also have knowledge of windows. I don't have any experience with open source previously.I am interested in Checks & Hashes module Regards Harinderpal Singh Website; http://www.iyouth.in Blog: http://codelinguist.wordpress.com/ <http://codelinguist.wordpress.com/> +91-9888573505

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