November 2006 - Boost-users - lists.preview.boost.org

Boost:ASIO mailing list/group
by Stas 10 Nov '06

10 Nov '06

What is a right group/ mailing list ot ask ASIO related questions? Regards Stas

3 6

locale for lexical_cast?
by Amin Kharchi 10 Nov '06

10 Nov '06

Hello! Is it possible to set a locale for the lexical_cast? It looks like that it is only possible to convert english/us numbers to a string? Example: float a = boost::lexical_cast<float>("12,3"); This would be in english 12.3. But I get a bad_cast exception for german numbers. A locale would be very helpful. Best regards Amin Kharchi

2 1

Lambda, how difficult should it be?
by Martin Young 10 Nov '06

10 Nov '06

Hi, I've just started trying to use the Boost lambda library and I'm finding that I can't get anything much to work how I'd expect. I've read the docs and I'm none the wiser. I'm running on Cygwin using GCC 3.4.4 if that makes any difference. My problem is pretty nebulous - I can't get the non-workingness nailed down a specific issue - whenever I try something different I get several screenfulls of different error messages. So, previously I had a alot of code in the form below which performs linear searches of a vector. Clearly this is not the Right Thing, especially as I will want to change the vectors to different containers at a later point. typedef struct { int a; void* b; } foo; vector<foo*>* v = buildAndPopulateVector(); for( int i=0, iL=v->size(); i<iL; i++ ) { foo* thisFoo = (*v)[i]; if( thisFoo->a == 0 ) { thisFoo->a = 1; *(int*)(thisFoo->b) = 42; } } Instead, I'd like to use the for_each algorithm to iterate over the contents of the vector like this: foreach( v->begin(), b->end(), ### ) Where the ### would normally be a function pointer (or relative thereof). I'd like to use lambda so I can put my code inline. At first I thought I could do something like: foreach( v->being(), b->end(), if_then( _1->a == 0, ( _1->a = 1, *(int*)(_1->b) = 42 ) ) I quickly discovered that the placeholders don't work like that and a pile of bind and/or ->* operators are required to extract any interesting information. I think I've got this bit sorted now though. What I'm getting stuck on now is constructing a working version of the if/then construct. The condition expression seems okay... if_then( bind(&foo::a,_1)==0, but I just can't get the "body" part to compile. I have to enclose it in round brackets so it appears as one expression to the compiler, but then it's not a lambda expression so I need to wrap it in something to make it a lambda. I should then pass _1 in as the single parameter of my new nested lambda because the previous _1 won't be in scope anymore - is this right? Is there another (better) way to include multiple expressions in an if_then construct without making a nested lambda and thus losing the bindings from the original lambda? What should I wrap my expression in to make it a unary lambda into which I can pass _1 from the main lambda? It's not getting automatically picked up as a lambda expression because the use of _1 is in the middle of one of the comma separated sub exprssions. Can I even pass _1 into a nested lambda like that or does it need massaging first? I've found dealing with the placeholders to be very painful so far... Are there any examples of this kind of thing anywhere? All the examples I've found are incomplete or for very trivial cases, or have not been answered. Even the "Beyond the std lib/boost" book has only very simple examples and esoteric gotchas. It seems to me this ought to be a very simple thing - am I going about it in the wrong way? I've had a good Google and a read through this list's archives and there seems to be very little discussion about the lambda library. Is it moribund or am I the only person who can't make it work? Sorry for all the rather vague questions and thanks for any pointers. -Martin.

2 1

binary_to_base64 example
by Kervin L. Pierre 10 Nov '06

10 Nov '06

Hello, Does someone have an example of how to use the base64_from_binary class to convert a 'char *' buffer to base64 text in a local buffer? I believe this is probably one of the simplest uses of the function but I can't make sense of the documentation. Best regards, Kervin

2 1

no output from BOOST_MESSAGE
by Kervin L. Pierre 09 Nov '06

09 Nov '06

Hello, I wrote a few simple test cases using Boost test, and things seem to work ok except done of my BOOST_MESSAGE() calls output anything. If the predicate fails for BOOST_REQUIRE_MESSAGE() I do get the message outputed to the screen, but not for regular BOOST_MESSAGE() Is there a setting that I should tune to output BOOST_MESSAGE, or may suppress BOOST_MESSAGE? Also I saw in a message somewhere that these functions can output to other targets than the screen. If that is the case, how do I go about doing this? Best regards, Kervin

2 6

[program_options] define precedent options?
by Rui Maciel 09 Nov '06

09 Nov '06

I've just discovered boost's program_options and at first glance it looked exactly what I was searching for, which was a easy to use library which was capable of handling the command line arguments parsing in a fast and efficient way. Unfortunately one of the things which I had my mind set to was the possibility of defining precedent options. To put it in other words, enable the parser to accept some options only if they were casted in a particular order and complain if that order wasn't respected. For example, accepting something like: app --add --file but complain if the arguments are like: app --file --add or app --add One other thing that I was hoping that boost's program_options was capable of handling was some sort of semantic interpretation according to the option's orders. Take this case for example: app --add --file --remove --file What I was hoping for was that program_options was capable of interpreting the first invocation of --file as relating to --add and the second invocation relating to --remove, instead of intepreting as two distinct invocations of --file. So, is it possible to accomplish that with boost's program_options? If so, could anyone be so kind to provide a simple example? Thanks in advance Rui Maciel -- Running Kubuntu 6.10 with KDE 3.5.5 and proud of it. jabber:rui_maciel@jabber.org

1 0

efficient string to numeric conversion (and vice-versa)
by Maitre Bart 09 Nov '06

09 Nov '06

Is there a Boost lib that offers efficient string to numeric type conversion ? What about numeric to string conversion ?

3 2

Ann: Alpha release of Boost.TR1-1.34
by John Maddock 09 Nov '06

09 Nov '06

I've placed an alpha release of the TR1 subset of Boost on the sourceforge download page: https://sourceforge.net/project/showfiles.php?group_id=7586&package_id=1893… Eventually, this package will track Boost-1.34 releases, but until that happens, I wanted to test the water and see how a subset like this would be received, and how best to organise it's packaging etc. So any feedback you have would be most welcome! The subset includes: TR1 Reference Wrappers Shared_ptr result_of mem_fn Function Object Binders Polymorphic Function Wrappers Type Traits Random Numbers Tuples Array Hash Functions Regular Expressions Complex Number Algorithms Enjoy! Regards, John Maddock.

1 0

Add library to link against in Jamfile (building a Boost.python extension)
by Alexander Eisenhuth 09 Nov '06

09 Nov '06

Hello, I'm writing a Boost.python extension, that needs the Boost.thread library. I use the Jamfiles from Boost.python example (works, except of linking), and need to add the thread library. How can I do that? Jamfiele: ---------------------------------------------- # This is the top of our own project tree project-root ; # Include definitions needed for Python modules import python ; # ----- getting_started1 ------- # Declare a Python extension called getting_started1 extension getting_started1 : # sources getting_started1.cpp # requirements and dependencies for Boost.Python extensions <template>@boost/libs/python/build/extension ; ------------------------------------------------- Thanks a lot Regards Alexander

2 1

undefined reference to `boost::read_graphviz
by Teodora Miteva 09 Nov '06

09 Nov '06

Hi, i got this problem when i tried to compile the graphviz.cpp: ------------------------- undefined reference to `boost::read_graphviz(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, boost::subgraph<boost::adjacency_list<boost::vecS, boost::vecS, boost::undirectedS, boost::property<boost::vertex_attribute_t, std::map<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> > const, std::basic_string<char, std::char_traits<char>, std::allocator<char> > > > >, boost::no_property>, boost::property<boost::edge_attribute_t, std::map<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> > const, std::basic_string<char, std::char_traits<char>, std::allocator<char> > > > >, boost::property<boost::edge_index_t, int, boost::no_property> >, boost::property<boost::graph_graph_attribute_t, std::map<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> > const, std::basic_string<char, std::char_traits<char>, std::allocator<char> > > > >, boost::property<boost::graph_vertex_attribute_t, std::map<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> > const, std::basic_string<char, std::char_traits<char>, std::allocator<char> > > > >, boost::property<boost::graph_edge_attribute_t, std::map<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> > const, std::basic_string<char, std::char_traits<char>, std::allocator<char> > > > >, boost::property<boost::graph_name_t, std::basic_string<char, std::char_traits<char>, std::allocator<char> >, boost::no_property> > > >, boost::listS> >&)' --------------------------------- i saw the explanation and some previous mails but still i have the problem... i built the lib libbgl-viz.a following the instructions ( http://www.cs.brown.edu/~jwicks/boost/libs/graph/doc/read-graphviz.html<http://www.cs.brown.edu/%7Ejwicks/boost/libs/graph/doc/read-graphviz.html>) , but still doesnt work ......... could you tell me what i could i do to salve it? thanks best teodora

1 0

converting a string to a function name
by Fred J. 09 Nov '06

09 Nov '06

Hi is there a way to convert a string to a function name and fire it. like void his_fun(){ cout << "his is here" << endl; } vector<string> vec; vec.push_back("his"); vec.push_back("me"); for(i=0; i<vec.size(); i++) string var = vec[i] + _fun; fire(var); and it will fire the routine "his_fun? is so, how? what whole idea is to avoid typing vector<func_ptr> vec; vec.push_back( &func_1 ); vec.push_back( &func_n ); ... thanks --------------------------------- Everyone is raving about the all-new Yahoo! Mail.

2 1

got a bad_any_cast exception
by ClassyK_Danad 09 Nov '06

09 Nov '06

#include <iostream> #include <boost/any.hpp> template<typename A, typename B> boost::any min(const A& a,const B& b) { return a < b ? a : b; } void main() { //got a bad_any_cast exception ! std::cout << boost::any_cast<int>( min( 1, 1.1)) << std::endl; } how could this happen?

3 3

Re: [Boost-users] Socket and iostream
by Nat Goodspeed 09 Nov '06

09 Nov '06

> -----Original Message----- > From: boost-users-bounces(a)lists.boost.org [mailto:boost-users- > bounces(a)lists.boost.org] On Behalf Of Jakub Stachowski > Sent: Wednesday, November 08, 2006 2:22 AM > To: boost-users(a)lists.boost.org > Subject: Re: [Boost-users] Socket and iostream > > > nothing seems to be written nor readen to/from the socket except for > > the first getline. What am I doing wrong here ? > > Try flushing the stream after each write. [Nat] I wondered about that -- but doesn't std::endl implicitly flush?

3 2

Re: [Boost-users] Sequence of Types, What For?
by james.jones＠firstinvestors.com 09 Nov '06

09 Nov '06

From: "Andrew Holden" <aholden(a)charteroaksystems.com> > 3: Look up the value in the first array, and then look up the code block > number in the second array. > > 4: Go to the pointer you just got. > > The actual blocks of code are laid out in order right after the goto in > step 4, in the same order as the source code. Breaks become goto end of > switch. If you leave out a break, the processor really does JUST fall > through to the next case. > > All in all, if you have a monster switch statement, the > compiler-generated code probably is just about as fast as you can get. > It takes less than a dozen machine instructions to implement it, and it > has constant complexity. Actually this is not particularly good. For one thing, it's O(n), not constant time, because doing an array lookup is O(n). For many switch use-cases this is no big deal, but it certainly isn't unheard of to have a switch with dozens (or more) of cases, each of which does almost nothing (like return a value). In this case, the lookup can actually dominate your runtime. There's a theorem in hash theory (proved by Komlos, one of my old profs) that says that you can always generate a perfect hash function if you know the values you need to hash. That is, you can generate a hash function that requires exactly one lookup in every case. But I don't know any compiler that actually does this. Since all cases are known at compile time, doing this should be a beneficial runtime optimization for large switches (if the generated hash function is sufficiently cheap). Maybe this could be done using the MPL? I don't know TMP well enough to know where to begin on something like this. See http://en.wikipedia.org/wiki/Perfect_hash_function for more detail. - James Jones Administrative Data Mgmt. Webmaster 375 Raritan Center Pkwy, Suite A Data Architect Edison, NJ 08837

5 5

BOOST_FOREACH VC8 warning: change in behavior
by Nico Galoppo 08 Nov '06

08 Nov '06

Hi, I'm getting the following warning in VC8, using BOOST_FOREACH on a container of shared_ptr<>s. The container itself is also a shared_ptr. warning C4686: 'boost::foreach_detail_::make_probe' : possible change in behavior, change in UDT return calling convention The warning happens at the following line shared_ptr<Scene> scene(new Scene()); typedef shared_ptr<Character> character_ptr; BOOST_FOREACH(character_ptr & actor, *scene) { ... } Unfortunately, I can't reproduce it in a simple program, it doesn't give me the warning there. --nico

2 2

Re: [Boost-users] [Boost.Filesystem] problem to link an executabl e to boost_filesys tem static library on Windows XP
by Johan.GUIHENEUF＠external.thalesgroup.com 08 Nov '06

08 Nov '06

Hello Rush and everybody, Thank you for your answer. Unfortunately, it does NOT match the name. The name computed "by auto_link.hpp" is boost_filesystem-vc71-mt-s-1_33.lib and the name of the static library on my computer is boost_filesystem-vc71-mt-1_33.lib (without the '-s'). So my problem is a problem of name mismatch, not a problem of project configuration for linking. Thank you. Johan GUIHENEUF -----Message d'origine----- De : boost-users-bounces(a)lists.boost.org [mailto:boost-users-bounces@lists.boost.org] De la part de Rush Manbert Envoyé : mardi 7 novembre 2006 20:40 À : boost-users(a)lists.boost.org Objet : Re: [Boost-users] [Boost.Filesystem] problem to link an executable to boost_filesys tem static library on Windows XP Johan.GUIHENEUF(a)external.thalesgroup.com wrote: > Hello, > > I try to build an console executable that uses boost_fileystem library. > I have got the file boost_filesystem-vc71-mt-1_33.lib. My IDE is Visual C++ 7.1. > I set the preprocessor definition _MT. > At build step, I have this error: "could not find boost_filesystem-vc71-mt-s-1_33.lib". > I had a look to boost/config/auto_link.hpp to see what "#define" I forgot but I do not understand why it chooses "#define BOOST_LIB_RT_OPT -s". > > hat preprocessor macro should I define to make it choose "#define BOOST_LIB_RT_OPT" (i.e. empty) ? Is there a blocking problem with Visual C++ 7.1 on Windows XP ? > Hi Johan, If you have verified that the library name generated by the auto link (boost_filesystem-vc71-mt-s-1_33.lib) matches what was installed by the boost build, then it looks like you didn't define the path to the library for the linker. This should be settable via the linker preferences, but I use VS 2005, so don't know how you would do it. - Rush _______________________________________________ Boost-users mailing list Boost-users(a)lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users

3 2

unit_test_result: is it deprecated?
by Stephen Torri 08 Nov '06

08 Nov '06

Is the class unit_test_result deprecated? I have boost 1.33.1 installed and it is not a part of the installation. Is there something else I am suppose to be using? Stephen

2 5

[regex] boost, problem compiling doc example of boost::match_extra
by Rick Weiss 08 Nov '06

08 Nov '06

I am trying to use the repeat capture mechanism in regex i thought i would start with the documentation example, but im having problems compiling it. Any help is appreciated. (There is likely a problem between my seat and the keyboard) Here is my compile output: and below that is the actual example. /usr/bin/g++ -Wno-ctor-dtor-privacy -O -o file2AssocTable.o -I/afs/apd.pok.ibm.com/func/vlsi/eclipz/common/integration/OA_migration/OpenAccess/2.2.4/include/oa \ -I/afs/apd.pok.ibm.com/func/vlsi/eclipz/common/integration/OA_migration/OpenAccess/2.2.4/include -I/afs/apd.pok.ibm.com/func/vlsi/eclipz/common/integration/GNU/boost/boost_1_33_1/include/boost-1_33_1 \ -c file2AssocTable.cpp file2AssocTable.cpp: In function `void print_captures(const std::string&, const std::string&)': file2AssocTable.cpp:171: no matching function for call to ` boost::match_results<__gnu_cxx::__normal_iterator<const char*, std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<boost::sub_match<__gnu_cxx::__normal_iterator<const char*, std::basic_string<char, std::char_traits<char>, std::allocator<char> > > > > >::captures(unsigned int&)' file2AssocTable.cpp:177: no matching function for call to ` boost::match_results<__gnu_cxx::__normal_iterator<const char*, std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<boost::sub_match<__gnu_cxx::__normal_iterator<const char*, std::basic_string<char, std::char_traits<char>, std::allocator<char> > > > > >::captures(unsigned int&)' make: *** [file2AssocTable.o] Error 1 void print_captures(const std::string& regx, const std::string& text) { boost::regex e(regx); boost::smatch what; std::cout << "Expression: \"" << regx << "\"\n"; std::cout << "Text: \"" << text << "\"\n"; if(boost::regex_match(text, what, e, boost::match_extra)) { unsigned i, j; std::cout << "** Match found **\n Sub-Expressions:\n"; for(i = 0; i < what.size(); ++i) std::cout << " $" << i << " = \"" << what[i] << "\"\n"; std::cout << " Captures:\n"; for(i = 0; i < what.size(); ++i) { std::cout << " $" << i << " = {"; for(j = 0; j < what.captures(i).size(); ++j) { if(j) std::cout << ", "; else std::cout << " "; std::cout << "\"" << what.captures(i)[j] << "\""; } std::cout << " }\n"; } } else { std::cout << "** No Match found **\n"; } }

2 3

[lambda] if-then-else construct gets broken by lambda-lib
by Sebastian Weber 08 Nov '06

08 Nov '06

Hello everybody! I'm trying to store a reference to a function depending upon a condition within a function object like this: boost::function< double (std::size_t) > wf = (sIndex < m_maxIndex+1) ? ( boost::lambda::bind(boost::ref(m_cf), sDeg, boost::lambda::_1) ) : ( boost::ref(*m_wf) ); However, this does not compile. The error message is: error: no match for ternary 'operator?:' in '(sIndex < (((boost::cor_cm_iterator4<RandomGenerator, Graph>*)this)->boost::cor_cm_iterator4<RandomGenerator, Graph>::m_maxIndex + 1)) ? boost::lambda::bind(boost::ref(((boost::cor_cm_iterator4<RandomGenerator, Graph>*)this)->boost::cor_cm_iterator4<RandomGenerator, Graph>::m_cf), sDeg, boost::lambda::<unnamed>::_1) : boost::ref((*((boost::cor_cm_iterator4<RandomGenerator, Graph>*)this)->boost::cor_cm_iterator4<RandomGenerator, Graph>::m_wf))' But the lengthy code boost::function< double (std::size_t) > wf; if(sIndex < m_maxIndex+1) wf = boost::lambda::bind(boost::ref(m_cf), sDeg, boost::lambda::_1); else wf = boost::ref(*m_wf); compiles fine. Any idea? How can lambda eat up the ? : construct? How do I prevent that? My system is a ubunut edgy which means, I have g++ 4.1 and use boost 1.33.1. Greetings, Sebastian Weber

3 3

Dependencies between boost libraries
by Loïc Joly 08 Nov '06

08 Nov '06

Hello, I was curious to know wether there was somewhere available a graph of dependencies between boost libraries ? Best regards, -- Loïc

3 4

Socket and iostream
by Ivan LAURETTE 08 Nov '06

08 Nov '06

Darwin 8.8.0 Boost 1.33.1 gcc 4.0.1 Hello, I want to establish a SMTP connection through a socket, then dialog with the server using a stream. I thought I could to it like this: //-------------------------------------------- #include <boost/iostreams/stream.hpp> #include <boost/iostreams/device/file_descriptor.hpp> using namespace std; using namespace boost::iostreams; ... int theSocket = socket(AF_INET,SOCK_STREAM,0); connect(theSocket, ...); file_descriptor fdDevice(theSocket); stream_buffer<file_descriptor> fdstream(fdDevice); iostream os(&fdstream); string answer; getline(os, answer); cout << answer << endl; os << "HELO xxxxx" << endl; getline(os, answer); cout << answer << endl; os << "MAIL FROM: <xxx.xxx(a)xxx.xxx>" << endl; getline(os, answer); cout << answer << endl; ... //-------------------------------------------- But nothing seems to be written nor readen to/from the socket except for the first getline. What am I doing wrong here ? Thanks in advance for any help.

2 1

[asio] Breaking changes committed to cvs HEAD
by Christopher Kohlhoff 08 Nov '06

08 Nov '06

I have just committed some asio changes to cvs HEAD that will break application code. These changes are part of what's needed to bring the interface into sync with the TR2 proposal. The big change is to the error handling classes, as described below. An async handler of the form: void my_handler(const boost::asio::error& e); becomes: void my_handler(const boost::system::error_code& e); Synchronous error handling like this: boost::asio::error e; sock.connect(ep, boost::asio::assign_error(e)); becomes: boost::system::error_code e; sock.connect(ep, e); And where previously a boost::asio::error exception was thrown, the new exception thrown is boost::system::system_error. Error constants like boost::asio::error::eof stay as they are, i.e.: void my_handler(const boost::system::error_code& e) { if (e == boost::asio::error::eof) { ... } } Programs will now need to link against the boost.system library (which is where boost::system::error_code and boost::system::system_error reside). Once I do a few more TR2-related changes I will post regenerated doxygen documentation to the vault. Stay tuned. Cheers, Chris

1 0

[Threads]Exception-safety of thread_group::add_thread
by Ai Azuma 08 Nov '06

08 Nov '06

Hi, I have questions about `boost::thread_group::add_thread' member function. The documents don't seem to say anything about exception-safety of this function. Therefore, I have questions; 1. Is this no-throw? 2. If the answer to 1. is "no", then how does it treat the ownership of its argument when an exception is thrown? Could anyone help me? Thanks in advance. -- Ai Azuma <ai.azuma(a)gmail.com>

1 0

progress_display+CProgressBar MFC
by Gennady Khokhorin 07 Nov '06

07 Nov '06

I'm wonder what could be a schema to connect boost::progress_timer to MFC CProgressBar (msvc) gui? Thanks in advance. gok

2 1

[Boost.Filesystem] problem to link an executable to boost_filesys tem static library on Windows XP
by Johan.GUIHENEUF＠external.thalesgroup.com 07 Nov '06

07 Nov '06

Hello, I try to build an console executable that uses boost_fileystem library. I have got the file boost_filesystem-vc71-mt-1_33.lib. My IDE is Visual C++ 7.1. I set the preprocessor definition _MT. At build step, I have this error: "could not find boost_filesystem-vc71-mt-s-1_33.lib". I had a look to boost/config/auto_link.hpp to see what "#define" I forgot but I do not understand why it chooses "#define BOOST_LIB_RT_OPT -s". hat preprocessor macro should I define to make it choose "#define BOOST_LIB_RT_OPT" (i.e. empty) ? Is there a blocking problem with Visual C++ 7.1 on Windows XP ? Thank you. Johan GUIHENEUF

2 1