September 2007 - Boost-users

A tuple performance question
by Peng Yu 05 Oct '07

05 Oct '07

Hi, It is mentioned at http://www.boost.org/libs/tuple/doc/tuple_users_guide.html#performance that the following two ways would be different in term of performance. ////////////// void f1(int&, double&); tuple<int, double> f2(); //Then, the call #1 may be slightly faster than #2 in the code below: int i; double d; ... f1(i,d); // #1 tie(i,d) = f2(); // #2 /////////////////// What about the current commonly used compiler, such as GCC? Are #1 and #2 different in GCC? Does the compiler always have some way to optimize #2 to make it as good as #1? Is it just a matter of fact whether the optimization method is implemented? Or #2 can never be made as good as #1? Thanks, Peng

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[Iostreams] Issue with mapped_file
by JD 04 Oct '07

04 Oct '07

Hello, There is something I don't get with mapped_file from the IOStreams library. Here is an example: // Code snippet #include <iostream> #include <boost/iostreams/device/mapped_file.hpp> #include <boost/iostreams/stream.hpp> using namespace boost::iostreams; int main(int argc, char **argv) { if (argc != 2) return 1; try { stream <mapped_file_sink> out; mapped_file_params p(argv[1]); p.new_file_size = 1024 * sizeof (char); out.open(mapped_file_sink(p)); } catch (const std::exception &e) { std::cout << e.what() << std::endl; return 2; } return 0; } // Code snippet When compiled, the execution goes like: c:\>test_shmem somefile c:\>test_shmem somefile failed setting file size: The handle is invalid. I tried without the new_file_size, I tried with a mapped_file... Is there something I don't get? Why are we not able to open a file that already exist? Thanks for your help. JD

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boost-users: boost enable_if
by chun ping wang 04 Oct '07

04 Oct '07

template <typename T> bool boost::pseudoprime(const T& n, const T& k) { typedef boost::operators<T> operatorT; BOOST_STATIC_ASSERT(is_integral<T>::value); // static assert 1. BOOST_STATIC_ASSERT((is_base_of<operatorT, T>::value)); // static assert 2. BOOST_ASSERT (n > T(2) && n % T(2) != 0); return modular_expo(k, n-1, n) != T(1) % n ? true : false; } now in vistual studio 2005 sp1 and visual studio 2008 beta the part "is_base_of<operatorT, T>::value" does not work if T happens to be an int or long due to "error C2803: 'operator --' must have at least one formal parameter of class type". I want to use enable_if to enable the STATIC_ASSERT only if T is NOT an arithmetic type for static assert 2. How would i go about doing that?

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Boost cookbook site (alpha)
by Kirit Sælensminde 02 Oct '07

02 Oct '07

I've spent the weekend putting together a cookbook site. I hope nobody minds. People can explore and play with it at http://www.boostcookbook.com/ Any problems, issues or suggestions can be reported at http://www.boostcookbook.com/Site:/Issues Apart from a couple of ASP pages using JavaScript the site is in C++ and makes heavy use of Boost :) Kirit

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Bjam linking problem
by desai3＠cooper.edu 02 Oct '07

02 Oct '07

Hi folks: I have successfully wrapped up a C++ program in Python. Now I want to give my libboost_python.so and server.so files to my friend, so that he can use it too. However server.so makes use of libstdc++ and ssl library files, which I have to link statically to the server.so in order to be able to give server.so to someone. However Bjam is not linking libstdc++.a or libssl.a to server.so statically. I will really appreciate if someone could give me any direction about how to link these libraries statically to server.so . Thank you very much. Maulik P.S. My Jamfile looks like this ----------------------------------------------------------------------- project-root ; import python ; extension server : server.cpp <template>@boost/libs/python/build/extension : <include>. <include>../dqp <include>/export/apps/dq/dqweb/include <library-path>/home/o066144/work_in_progress/api/SunOS-5.8-g++ <library-path>/export/apps/dq/dqweb/lib <library-path>/usr/local/lib <find-library>ssl <find-library>crypto <find-library>dl <find-library>socket <find-library>nsl <find-library>gcc <find-library>stdc++ ; ---------------------------------------------------------------------------

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Boost license / OSI approved
by Ruediger Berlich 01 Oct '07

01 Oct '07

Hi there, I noticed that the Boost license is not listed as an OSI approved license (see here: http://www.opensource.org/licenses/alphabetical ). Why is this ? The license seems to nicely comply with the Open Source definition, from what I can see (see http://www.opensource.org/docs/osd) http://www.fsf.org/licensing/licenses/ lists it as GPL-compatible. Best Regards, Ruediger

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u32regex_search crashes
by Anjaly 01 Oct '07

01 Oct '07

Hello, I am new to Boost-regex library. The libray is build with icu support.The user interface is created using wxWidgets library. I want to search a file using u32regex_search. But the program crashes and the error it shows is 'Invalid UTF-8 sequence encountered while trying to encode UTF-32 character'.I am reading the contents of the file and it is stored in char array.The program is crashing when it encounters a char with hex value 00. wxString s=SearchTxt->GetValue(); const char *start=(const char*)buffer; const char *end=(const char*)buffer+len; boost::cmatch what; boost::u32regex e1= boost::make_u32regex(s.fn_str(), boost::regex::icase); while(boost::u32regex_search(start,end, what,e, boost::match_default)) { cout << what[0] << "\n"; } ______________________________________ Scanned and protected by Email scanner

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string_algo no replace_if
by gast128 01 Oct '07

01 Oct '07

Dear all I was requesting an 'erase_if' a while ago, and now I ran into a 'replace_if' problem. So after spendig 2 hours in the documentation, I finally found on www ('[string_algo] replace repeated char with single instance?') that one should use the 'find_format_all': boost::find_format_all(str, boost::token_finder(boost::is_any_of("ab")), boost::const_formatter("c")); But wouldn't it be better to make a 'replace_if' shortcut solely for the purpose of documentation reasons: boost::replace_all_if(str, boost::is_any_of("ab"), "c"); I think that most people find the last line easier to read and comprehend than its (more powerful) 'find_format' cousin. The string_algo library is nice but I get lost more than once. Especially find, replace, erease with predicates are often used by us. However direct use seems not possible. wkr, me

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Inquiring about the feasibility of boost::mpl based statechart DSELs that generate boost::statechart based components
by Tony Turner 30 Sep '07

30 Sep '07

Greetings; I am currently experimenting with the feasibility of writing a boost::mpl based library of metaprograms that process statechart DSEL language phrases ( see ref #1 below), that then specifically generate boost::statechart based components. I would be most grateful to hear from others regarding both difficulties to this approach, as well as success stories. If this approach seems feasible, I would like to contribute the resultant code back to the open source community. Since I'm not sure how the contribution process works, I would appreciate it if someone could point me in the right direction. Reference (#1) ( the statechart developed in chap 11, "A DSEL Design Walkthrough" in Abrahams and Gurtovoy's "C++ Template Metaprogramming book".) Thankyou very much for your time; Tony Turner R&D Software Engineer

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Re: [Boost-users] How does one build the asio system library?
by console shark 30 Sep '07

30 Sep '07

Yeah I mean Boost.System, but that wasn't part of the boost download, it seems to come with Asio, right? So now that I put the /system stuff in there, how does it get built? As far as I know it wasn't there prior to me putting it in the /boost/ directory. ----- Original Message ---- From: Richard Dingwall <rdingwall(a)gmail.com> To: boost-users(a)lists.boost.org Sent: Sunday, September 30, 2007 6:04:13 PM Subject: Re: [Boost-users] How does one build the asio system library? On 10/1/07, console shark <consolejoker(a)yahoo.com> wrote: The docs say to run bjam inside /boost/libs/system/build I did this, and it claims to have built the file but I can't fine it anywhere on my hard drive. Subsequent attempts to run bjam don't seem to do anything. The Asio library is header only. You don't need to build anything. You may however need to link against the Boost.System and Boost.Regex libraries. Richard ____________________________________________________________________________________ Got a little couch potato? Check out fun summer activities for kids. http://search.yahoo.com/search?fr=oni_on_mail&p=summer+activities+for+kids&…

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