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[mpl] Using at_c within find_if
by Christian Henning 29 Mar '07

29 Mar '07

Hi there, I'm trying to find a solution for looking for type vector containing a specific type. On another thread I was suggested to use at_c within the find_if algorithm. Unfortunately the code doesn't compile. #include "boost/mpl/vector.hpp" #include <boost/mpl/find_if.hpp> #include <boost/mpl/at.hpp> using namespace std; using namespace boost; typedef mpl::vector<char, char> vec_1; typedef mpl::vector<char, int> vec_2; typedef mpl::vector<vec_1, vec_2> mat; typedef mpl::find_if<mat, is_same<mpl::at_c<mpl::_1,1>, int> >::type iter; int _tmain(int argc, _TCHAR* argv[]) { BOOST_STATIC_ASSERT(( is_same< mpl::deref<iter>::type, vec_2 >::value )); return 0; } Might this be a bug in the MPL lib? Thanks for any help, Christian

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[MPL Book] FSM Question
by Ovanes Markarian 29 Mar '07

29 Mar '07

I have a question on the FSM Player from the MPL book. In the source sample you write in the main function: player p; // An instance of the FSM p.process_event(open_close()); // user opens CD player p.process_event(open_close()); // inserts CD and closes p.process_event( // CD is detected cd_detected( "louie, louie" , std::vector<std::clock_t>( /* track lengths */ ) ) ); p.process_event(play()); // etc. p.process_event(pause()); p.process_event(play()); p.process_event(stop()); This is nice but what if I have a real life case, where I don't know which event will arrive next? Then I need to dispatch the incoming event and convert it to the appropriate tag. Do I misunderstand it? When I read the book it seemed clear to me, but now I am in the situation where I could use it and I have doubts if I really understood it the way the authors thought... With Kind Regards, Ovanes

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Re: [Boost-users] boost::bind syntax with a vector of shared_ptrs and find_if usage
by Forever Kid 29 Mar '07

29 Mar '07

I was able to answer my own question after some additional reading. This: find_if(a_vector.begin(), a_vector.end(), bind(equal_to<string>(),bind(&dref,_1),string("with "))); is equivalent to: (?) find_if(a_vector.begin(), a_vector.end(), (bind(&dref, _1) == string("with "))); Please correct me if I am missing anything. There's a steep learning curve and I'm still on it. Thanks, Graham ----- Original Message ---- From: Forever Kid <foreverkid3(a)yahoo.com> To: boost-users(a)lists.boost.org Sent: Thursday, March 29, 2007 11:30:03 AM Subject: boost::bind syntax with a vector of shared_ptrs and find_if usage What is the syntax for the line below without using bind's overloaded '==' operator and instead using equal_to<>? an_iterator = find_if(a_vector.begin(), a_vector.end(), (bind(&dref, _1) == string("with "))); I am doing these as exercises in an attempt to wrap my head around boost::bind. What has me puzzled, at the moment, is how find_if 'knows' (above) to automatically compare what the share_ptrs are pointing to (the strings). Doesn't a_vector.begin() return an iterator to a shared_ptr and not a string? Thanks again, Graham Current working example: const string& dref(const shared_ptr<string> &sp) { return *sp; } int main (int argc, char *argv[]) { vector<shared_ptr<string> > a_vector; shared_ptr<string> sp1(new string("Play ")); shared_ptr<string> sp2(new string("with ")); shared_ptr<string> sp3(new string("C++!")); a_vector.push_back(sp1); a_vector.push_back(sp2); a_vector.push_back(sp3); vector<shared_ptr<string> >::iterator an_iterator; an_iterator = find_if(a_vector.begin(), a_vector.end(), (bind(&dref, _1) == string("with "))); if (an_iterator != a_vector.end()) { shared_ptr<string> sp(*an_iterator); cout << "Found " << *sp << endl; } return 0; } ----- Original Message ---- From: Jeff F <TriumphSprint2000(a)hotmail.com> To: boost-users(a)lists.boost.org Sent: Thursday, March 29, 2007 8:11:56 AM Subject: Re: [Boost-users] boost::bind syntax with a vector of weak_ptrs Forever Kid wrote: > What is the correct boost::bind syntax to use with a standard > algorithm such as find_if with an array of weak_ptrs or shared_ptrs > to an object such as a string? > > My weak attempt to figure this out is below: > > shared_ptr<string> sp1(new string("Play ")); > shared_ptr<string> sp2(new string("with ")); > shared_ptr<string> sp3(new string("C++!")); > > vector<weak_ptr<string> > a_vector; > > a_vector.push_back(weak_ptr<string>(sp1)); > a_vector.push_back(weak_ptr<string>(sp2)); > a_vector.push_back(weak_ptr<string>(sp3)); > > // What is the correct syntax here? > find_if(a_vector.begin(), a_vector.end(), (bind(&equal_to<string>(), > _1))(string("Play ")); The above has many problems unrelated to weak_ptrs. (bind(&equal_to<string>(),_1))(string("Play ")); |----------------------------||---------------| a b Part "a" above is not a properly formed bind expression: 1 - you are passing the address of an equal_to<...> instance. 2 - equal_to<...> expects two arguments you supply one. Part "b" attempts to invoke the function object resulting from Part "a", and passes the result(if part "a" were well formed); a bool to find_if. find_if then tries to apply operator() to the bool, which again is ill formed. The proper bind expression for comparing a string _value_ is: bind( equal_to<string>(), _1, string("Play ") ) To use this you'd need an indirect or transform iterator adaptor that derefs the weak ptrs. See http://www.boost.org/libs/iterator/doc/indirect_iterator.html http://www.boost.org/libs/iterator/doc/transform_iterator.html I'm not sure of the details in using an indirect iterator with weak_ptr. A transform iterator would require you to provide a deref function, and use it with the iterator adaptor library. This is untested code: std::string deref_wps( weak_ptr<string> wps ){ return /* derefed wps */; } find_if( make_transform_iterator(a_vector.begin(),&deref_wps) , make_transform_iterator(a_vector. end(),&deref_wps) , bind( equal_to<string>(), _1, string("Play ") ) ); Or using some of the nice operator overloading provided by bind, you can forego the iterator adaptors: find_if( a_vector.begin() , a_vector. end() , bind( &deref_wps, _1 ) == string("Play ") ); Jeff _______________________________________________ Boost-users mailing list Boost-users(a)lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users ____________________________________________________________________________________ Looking for earth-friendly autos? Browse Top Cars by "Green Rating" at Yahoo! Autos' Green Center. http://autos.yahoo.com/green_center/ ____________________________________________________________________________________ Be a PS3 game guru. Get your game face on with the latest PS3 news and previews at Yahoo! Games. http://videogames.yahoo.com/platform?platform=120121

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Building rc_1_34_0 (w/python)
by Kelly Burkhart 29 Mar '07

29 Mar '07

Greetings, I have downloaded the latest RC from cvs and am trying to build on Linux and Windows without success. Could someone nudge me in the right direction? On Linux (SuSE 10.1 x86-64), I've done this: cd ~/downloads/boost/rc_1_34_0_nearing_release cvs -d:pserver:anonymous@boost.cvs.sf.net:/cvsroot/boost login cvs -z3 -d:pserver:anonymous@boost.cvs.sf.net:/cvsroot/boost co -rRC_1_34_0 -P boost cd boost cd tools/jam/src/ . ./build.sh cd ../../../ I then created a user-config.jam file that looks like this: # Compiler configuration using gcc : : : <compileflags>-DBOOST_SIGNALS_NAMESPACE=tb_signals ; # Python configuration using python : 2.4 : /usr ; And then ran: > ./tools/jam/src/bin.linux/bjam --prefix=/opt/boost --build-dir=../build_dir stage Building Boost.Regex with the optional Unicode/ICU support disabled. Please refer to the Boost.Regex documentation for more information (don't panic: this is a strictly optional feature). warning: Python location is not configured warning: the Boost.Python library won't be built warning: No toolsets are configured. warning: Configuring default toolset "gcc". warning: If the default is wrong, you may not be able to build C++ programs. warning: Use the "--toolset=xxxxx" option to override our guess. warning: For more configuration options, please consult warning: http://boost.org/boost-build2/doc/html/bbv2/advanced/configuration.html <I interrupted build here> Why is python not found? I've used the following 'using python' lines in user-config.jam without success: using python ; using python : 2.4 ; using python : 2.4 : /usr ; using python : 2.4 : /usr/bin/python ; Similar steps on Windows (VS.net 2003), user-config.jam looks like this: # Compiler configuration using msvc : : : <compileflags>-DBOOST_SIGNALS_NAMESPACE=tb_signals ; # Python configuration using python : 2.5 : c:\python25 ; I've also tried: using python : 2.5 : c:\python25\python.exe ; Build command: C:\...>tools\jam\src\bin.ntx86\bjam.exe --build-dir=..\boost_build --prefix=c:\Boost Warning: "using python" expects a two part (major, minor) version number; got Python25 instead warning: No working Python interpreter found. warning: falling back to "python" Warning: "using python" expects a two part (major, minor) version number; got 0 instead Building Boost.Regex with the optional Unicode/ICU support disabled. Please refer to the Boost.Regex documentation for more information (don't panic: this is a strictly optional feature). ^C I'm sure there is some trivial thing I'm not doing correctly, however I'm not able to see it in the getting started pages. Is there some building_boost_for_non_bjam_gurus.html file that I'm not seeing? Thanks, -K

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boost::bind syntax with a vector of shared_ptrs and find_if usage
by Forever Kid 29 Mar '07

29 Mar '07

What is the syntax for the line below without using bind's overloaded '==' operator and instead using equal_to<>? an_iterator = find_if(a_vector.begin(), a_vector.end(), (bind(&dref, _1) == string("with "))); I am doing these as exercises in an attempt to wrap my head around boost::bind. What has me puzzled, at the moment, is how find_if 'knows' (above) to automatically compare what the share_ptrs are pointing to (the strings). Doesn't a_vector.begin() return an iterator to a shared_ptr and not a string? Thanks again, Graham Current working example: const string& dref(const shared_ptr<string> &sp) { return *sp; } int main (int argc, char *argv[]) { vector<shared_ptr<string> > a_vector; shared_ptr<string> sp1(new string("Play ")); shared_ptr<string> sp2(new string("with ")); shared_ptr<string> sp3(new string("C++!")); a_vector.push_back(sp1); a_vector.push_back(sp2); a_vector.push_back(sp3); vector<shared_ptr<string> >::iterator an_iterator; an_iterator = find_if(a_vector.begin(), a_vector.end(), (bind(&dref, _1) == string("with "))); if (an_iterator != a_vector.end()) { shared_ptr<string> sp(*an_iterator); cout << "Found " << *sp << endl; } return 0; } ----- Original Message ---- From: Jeff F <TriumphSprint2000(a)hotmail.com> To: boost-users(a)lists.boost.org Sent: Thursday, March 29, 2007 8:11:56 AM Subject: Re: [Boost-users] boost::bind syntax with a vector of weak_ptrs Forever Kid wrote: > What is the correct boost::bind syntax to use with a standard > algorithm such as find_if with an array of weak_ptrs or shared_ptrs > to an object such as a string? > > My weak attempt to figure this out is below: > > shared_ptr<string> sp1(new string("Play ")); > shared_ptr<string> sp2(new string("with ")); > shared_ptr<string> sp3(new string("C++!")); > > vector<weak_ptr<string> > a_vector; > > a_vector.push_back(weak_ptr<string>(sp1)); > a_vector.push_back(weak_ptr<string>(sp2)); > a_vector.push_back(weak_ptr<string>(sp3)); > > // What is the correct syntax here? > find_if(a_vector.begin(), a_vector.end(), (bind(&equal_to<string>(), > _1))(string("Play ")); The above has many problems unrelated to weak_ptrs. (bind(&equal_to<string>(),_1))(string("Play ")); |----------------------------||---------------| a b Part "a" above is not a properly formed bind expression: 1 - you are passing the address of an equal_to<...> instance. 2 - equal_to<...> expects two arguments you supply one. Part "b" attempts to invoke the function object resulting from Part "a", and passes the result(if part "a" were well formed); a bool to find_if. find_if then tries to apply operator() to the bool, which again is ill formed. The proper bind expression for comparing a string _value_ is: bind( equal_to<string>(), _1, string("Play ") ) To use this you'd need an indirect or transform iterator adaptor that derefs the weak ptrs. See http://www.boost.org/libs/iterator/doc/indirect_iterator.html http://www.boost.org/libs/iterator/doc/transform_iterator.html I'm not sure of the details in using an indirect iterator with weak_ptr. A transform iterator would require you to provide a deref function, and use it with the iterator adaptor library. This is untested code: std::string deref_wps( weak_ptr<string> wps ){ return /* derefed wps */; } find_if( make_transform_iterator(a_vector.begin(),&deref_wps) , make_transform_iterator(a_vector. end(),&deref_wps) , bind( equal_to<string>(), _1, string("Play ") ) ); Or using some of the nice operator overloading provided by bind, you can forego the iterator adaptors: find_if( a_vector.begin() , a_vector. end() , bind( &deref_wps, _1 ) == string("Play ") ); Jeff _______________________________________________ Boost-users mailing list Boost-users(a)lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users ____________________________________________________________________________________ Looking for earth-friendly autos? Browse Top Cars by "Green Rating" at Yahoo! Autos' Green Center. http://autos.yahoo.com/green_center/

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boost::format with empty string...
by Early Ehlinger 29 Mar '07

29 Mar '07

Using MS Visual C++ 2005, Express Edition, the following snippet causes an assertion failure due to a NULL pointer in the bowels of boost::format: boost::format f( "test %1%\n" ); f % ""; I traced it down to boost/format/feed_args.hpp: template<class Ch, class Tr, class Alloc> void mk_str( std::basic_string<Ch,Tr, Alloc> & res, const Ch * beg, typename std::basic_string<Ch,Tr,Alloc>::size_type size, std::streamsize w, const Ch fill_char, std::ios_base::fmtflags f, const Ch prefix_space, // 0 if no space-padding bool center) // applies centered/left/right padding to the string [beg, beg+size[ // Effects : the result is placed in res. { typedef typename std::basic_string<Ch,Tr,Alloc>::size_type size_type; res.resize(0); if( ( w<=0 || static_cast<size_type>(w) <=size)) { // no need to pad. res.reserve(size + !!prefix_space); if(prefix_space) res.append(1, prefix_space); res.append(beg, size); <<--- crashes, because beg==NULL and size==0 ... My suggested fix looks like this: template<class Ch, class Tr, class Alloc> void mk_str( std::basic_string<Ch,Tr, Alloc> & res, const Ch * beg, typename std::basic_string<Ch,Tr,Alloc>::size_type size, std::streamsize w, const Ch fill_char, std::ios_base::fmtflags f, const Ch prefix_space, // 0 if no space-padding bool center) // applies centered/left/right padding to the string [beg, beg+size[ // Effects : the result is placed in res. { typedef typename std::basic_string<Ch,Tr,Alloc>::size_type size_type; res.resize(0); if(size && ( w<=0 || static_cast<size_type>(w) <=size)) { // no need to pad. res.reserve(size + !!prefix_space); if(prefix_space) res.append(1, prefix_space); res.append(beg, size); } else { std::streamsize n=static_cast<std::streamsize>(w-size-!!prefix_space); std::streamsize n_after = 0, n_before = 0; res.reserve(w); // allocate once for the 2 inserts if(center) n_after = n/2, n_before = n - n_after; else if(f & std::ios_base::left) n_after = n; else n_before = n; // now make the res string : if(n_before) res.append(n_before, fill_char); if(prefix_space) res.append(1, prefix_space); if ( size ) res.append(beg, size); if(n_after) res.append(n_after, fill_char); } } // -mk_str(..) -- Early Ehlinger, President, ResPower, Inc.

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[bjam / mingw] filesystem, signals, serialization build error
by Cyril Delmas 29 Mar '07

29 Mar '07

Hello all, I have some trouble while building boost with mingw : I can't build neither filesystem, signals, nor serialization. "bjam -sTOOLS=mingw install" fails while linking with many "undefined reference" error messages. Am I missing something ? Thanks in advance.

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Re: [Boost-users] boost::bind syntax with a vector of weak_ptrs
by Forever Kid 29 Mar '07

29 Mar '07

Thanks Jeff. I am catching on. This code worked well: (for shared_ptrs) const string& dref(const shared_ptr<string> &sp) { return *sp; } int main (int argc, char *argv[]) { vector<shared_ptr<string> > a_vector; shared_ptr<string> sp1(new string("Play ")); shared_ptr<string> sp2(new string("with ")); shared_ptr<string> sp3(new string("C++!")); a_vector.push_back(sp1); a_vector.push_back(sp2); a_vector.push_back(sp3); vector<shared_ptr<string> >::iterator an_iterator; an_iterator = find_if(a_vector.begin(), a_vector.end(), (bind(&dref, _1) == string("with "))); if (an_iterator != a_vector.end()) { shared_ptr<string> sp(*an_iterator); cout << "Found " << *sp << endl; } return 0; } Kindly, Graham ----- Original Message ---- From: Jeff F <TriumphSprint2000(a)hotmail.com> To: boost-users(a)lists.boost.org Sent: Thursday, March 29, 2007 8:11:56 AM Subject: Re: [Boost-users] boost::bind syntax with a vector of weak_ptrs Forever Kid wrote: > What is the correct boost::bind syntax to use with a standard > algorithm such as find_if with an array of weak_ptrs or shared_ptrs > to an object such as a string? > > My weak attempt to figure this out is below: > > shared_ptr<string> sp1(new string("Play ")); > shared_ptr<string> sp2(new string("with ")); > shared_ptr<string> sp3(new string("C++!")); > > vector<weak_ptr<string> > a_vector; > > a_vector.push_back(weak_ptr<string>(sp1)); > a_vector.push_back(weak_ptr<string>(sp2)); > a_vector.push_back(weak_ptr<string>(sp3)); > > // What is the correct syntax here? > find_if(a_vector.begin(), a_vector.end(), (bind(&equal_to<string>(), > _1))(string("Play ")); The above has many problems unrelated to weak_ptrs. (bind(&equal_to<string>(),_1))(string("Play ")); |----------------------------||---------------| a b Part "a" above is not a properly formed bind expression: 1 - you are passing the address of an equal_to<...> instance. 2 - equal_to<...> expects two arguments you supply one. Part "b" attempts to invoke the function object resulting from Part "a", and passes the result(if part "a" were well formed); a bool to find_if. find_if then tries to apply operator() to the bool, which again is ill formed. The proper bind expression for comparing a string _value_ is: bind( equal_to<string>(), _1, string("Play ") ) To use this you'd need an indirect or transform iterator adaptor that derefs the weak ptrs. See http://www.boost.org/libs/iterator/doc/indirect_iterator.html http://www.boost.org/libs/iterator/doc/transform_iterator.html I'm not sure of the details in using an indirect iterator with weak_ptr. A transform iterator would require you to provide a deref function, and use it with the iterator adaptor library. This is untested code: std::string deref_wps( weak_ptr<string> wps ){ return /* derefed wps */; } find_if( make_transform_iterator(a_vector.begin(),&deref_wps) , make_transform_iterator(a_vector. end(),&deref_wps) , bind( equal_to<string>(), _1, string("Play ") ) ); Or using some of the nice operator overloading provided by bind, you can forego the iterator adaptors: find_if( a_vector.begin() , a_vector. end() , bind( &deref_wps, _1 ) == string("Play ") ); Jeff _______________________________________________ Boost-users mailing list Boost-users(a)lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users ____________________________________________________________________________________ Get your own web address. Have a HUGE year through Yahoo! Small Business. http://smallbusiness.yahoo.com/domains/?p=BESTDEAL

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How to build Boost 1.34 iostreams
by Johan Råde 29 Mar '07

29 Mar '07

In the past, when I built Boost 1.33, I used the command bjam -sTOOLS=vc-7_1 -sZLIB_INCLUDE=C:/Qt/3.3.7/src/3rdparty/zlib stage This worked fine. Now I tried to build Boost RC 1.34. The best I could come up with was bjam --toolset=msvc-7.1 --ZLIB_INCLUDE=C:/Qt/3.3.7/src/3rdparty/zlib stage This does not work. The iostreams library is not built. All other libraries are built just fine though. I searched the build log for the string iostreams and zlib, and found nothing. How do I build the iostreams library, with Boost 1.34 and the above zlib headers path? -- Johan Råde

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boost::bind syntax with a vector of weak_ptrs
by Forever Kid 29 Mar '07

29 Mar '07

What is the correct boost::bind syntax to use with a standard algorithm such as find_if with an array of weak_ptrs or shared_ptrs to an object such as a string? My weak attempt to figure this out is below: shared_ptr<string> sp1(new string("Play ")); shared_ptr<string> sp2(new string("with ")); shared_ptr<string> sp3(new string("C++!")); vector<weak_ptr<string> > a_vector; a_vector.push_back(weak_ptr<string>(sp1)); a_vector.push_back(weak_ptr<string>(sp2)); a_vector.push_back(weak_ptr<string>(sp3)); // What is the correct syntax here? find_if(a_vector.begin(), a_vector.end(), (bind(&equal_to<string>(), _1))(string("Play ")); Thanks, Graham ____________________________________________________________________________________ Never miss an email again! Yahoo! Toolbar alerts you the instant new Mail arrives. http://tools.search.yahoo.com/toolbar/features/mail/

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