December 2004 - Boost-users

boost::serialize on Codewarrior 8.3 (Mac)
by Ryan Wilcox 22 Dec '04

22 Dec '04

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hello all, I would like to use boost::serialize for one of my projects, using Codewarrior 8.3 (going to CW 9 may or may not be in the picture), on Mac OS X (10.3.x) Anyway, I've been working on getting the unit tests for boost::serialize up and running inside the Codewarrior IDE. I created a new project file (C++, Mac OS Carbon, Console), included a serialize unit test, set the paths correctly, included the files I thought I would need for boost::test stuff, all that jazz. The test that I'm trying out now, in the serialization test suite, is test_binary.cpp. Trying to compile it gave me some immediate compiler errors (which I fixed by #including some additional source files: "binary_archive.hpp", "stdio.h" (tmpnam is in stdio.h in CW, and not cstdio). At the end I have just one error which I don't understand (both because the error message is hard to parse, and I'm fairly new to the boost libraries in general). Here, for completeness, is the error message: Error : illegal use of abstract class ('boost::archive::detail::basic_iserializer::load_object_data(boost::archive::detail::basic_iarchive &, void *, const unsigned int) const') ~ (point of instantiation: 'test_main(int, char **)') ~ (instantiating: 'boost::archive::detail::interface_iarchive<boost::archive::binary_iarchive>::operator>><boost::serialization::nvp<A>>(const boost::serialization::nvp<A> &)') ~ (instantiating: 'boost::archive::binary_iarchive_impl<boost::archive::binary_iarchive>::load_override<boost::serialization::nvp<A>>(boost::serialization::nvp<A> &, int)') ~ (instantiating: 'boost::archive::basic_binary_iarchive<boost::archive::binary_iarchive>::load_override<boost::serialization::nvp<A>>(boost::serialization::nvp<A> &, int)') ~ (instantiating: 'boost::archive::load<boost::archive::binary_iarchive, boost::serialization::nvp<A>>(boost::archive::binary_iarchive &, boost::serialization::nvp<A> &)') ~ (instantiating: 'boost::archive::detail::load_non_pointer_type<boost::archive::binary_iarchive, boost::serialization::nvp<A>>::invoke(boost::archive::binary_iarchive &, boost::serialization::nvp<A> &)') ~ (instantiating: 'boost::archive::detail::load_non_pointer_type<boost::archive::binary_iarchive, boost::serialization::nvp<A>>::load_only::invoke(boost::archive::binary_iarchive &, boost::serialization::nvp<A> &)') ~ (instantiating: 'boost::serialization::serialize_adl<boost::archive::binary_iarchive, boost::serialization::nvp<A>>(boost::archive::binary_iarchive &, boost::serialization::nvp<A> &, const unsigned int)') ~ (instantiating: 'boost::serialization::serialize<boost::archive::binary_iarchive, boost::serialization::nvp<A>>(boost::archive::binary_iarchive &, boost::serialization::nvp<A> &, const unsigned int)') ~ (instantiating: 'boost::serialization::access::serialize<boost::archive::binary_iarchive, boost::serialization::nvp<A>>(boost::archive::binary_iarchive &, boost::serialization::nvp<A> &, const unsigned int)') ~ (instantiating: 'boost::serialization::nvp<A>::serialize<boost::archive::binary_iarchive>(boost::archive::binary_iarchive &, const unsigned int) const') ~ (instantiating: 'boost::archive::detail::interface_iarchive<boost::archive::binary_iarchive>::operator&<A>(A &)') ~ (instantiating: 'boost::archive::binary_iarchive_impl<boost::archive::binary_iarchive>::load_override<A>(A &, int)') ~ (instantiating: 'boost::archive::basic_binary_iarchive<boost::archive::binary_iarchive>::load_override<A>(A &, int)') ~ (instantiating: 'boost::archive::load<boost::archive::binary_iarchive, A>(boost::archive::binary_iarchive &, A &)') ~ (instantiating: 'boost::archive::detail::load_non_pointer_type<boost::archive::binary_iarchive, A>::invoke(boost::archive::binary_iarchive &, A &)') ~ (instantiating: 'boost::archive::detail::load_non_pointer_type<boost::archive::binary_iarchive, A>::load::invoke(boost::archive::binary_iarchive &, A &)') ~ (instantiating: 'boost::archive::detail::iserializer<boost::archive::binary_iarchive, A>::instantiate()') iserializer.hpp line 142 static iserializer instance; _____ I don't, really, understand why there's an error here, as iserializer is ~ a non-abstract type (as far as I can see), but it looks like there's plenty of template stuff going on, and there may be a clue in there. Does anyone have any pointers, or ideas on how I can fix this error? Thanks, _Ryan Wilcox ================================================================ Wilcox Development Solutions: http://www.wilcoxd.com Toolsmiths for the Internet Age PGP: 0x2F4E9C31 -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.6 (Darwin) Comment: Using GnuPG with Thunderbird - http://enigmail.mozdev.org iD8DBQFBx1BUbYO0qC9OnDERAtAcAJ4nR0Zff4hFRNQJzyVybmIO1DF7IwCff2LK 1KAnmA4JtS6AOvLgrJxVkF4= =/7gM -----END PGP SIGNATURE-----

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program_options custom type problem
by Jacques Kerner 22 Dec '04

22 Dec '04

Hi, I am trying to use a custom type with the program_options library, but I get the "invalid option value" error when running my application, although inline parameters are correctly read. Here is what I do : I define a class ApplicationLocator consisting of two integer members, "site" and "application" and the corresponding >> and << operator towards and from stringstream. The following method in lexical_cast.hpp returns false : bool operator>>(InputStreamable &output) { return !is_pointer<InputStreamable>::value && stream >> output && (stream >> std::ws).eof(); } which results in an exception being thrown eventually, by this code (also in lexical_cast.hpp) : template<typename Target, typename Source> Target lexical_cast(Source arg) { detail::lexical_stream<Target, Source> interpreter; Target result; if(!(interpreter << arg && interpreter >> result)) throw_exception(bad_lexical_cast(typeid(Target), typeid(Source))); return result; } The problem is that my >> operator returns true alright. Maybe I am wrong, but apparently what returns false is (stream >> std::ws).eof(); which I do not quite understand, let alone know how to avoid. Could someone kindly give me guidance on this ? Here is my custom type related code : #include <strstream> #include <boost/algorithm/string/split.hpp> #include <boost/lambda/lambda.hpp> class ApplicationLocator { public: ApplicationLocator() : site(0), application(0) {} ApplicationLocator(const int & aSite, const int & anApplication) : site(aSite), application(anApplication) {} int site; int application; }; bool operator>>(const std::stringstream & input, ApplicationLocator &output) { std::vector<std::string> splitString; boost::algorithm::split( splitString, std::string(input.str()), boost::lambda::_1=='.' ); if (splitString.size() > 1) { output.site = atoi(splitString[0].c_str()); output.application = atoi(splitString[1].c_str()); return true; } else { return true; } return true; } std::stringstream & operator<<(std::stringstream & output, const ApplicationLocator & input) { output << input.site << "." << input.application << '\0'; return output; } and the program_options related code : boost::program_options::positional_options_description positional; boost::program_options::variables_map configurationVariablesMap; try { boost::program_options::options_description desc("Allowed options"); desc.add_options() ("help,h", "produce help message") ("self-id,s", boost::program_options::value<ApplicationLocator>()->default_value(ApplicationLocator(1,1)), "This application's DIS identifier : site.application (separated by a dot)") ("instructor-id,i", boost::program_options::value<ApplicationLocator>()->default_value(ApplicationLocator(2,1)), "This instructor's DIS identifier : site.application (separated by a dot)") ; boost::program_options::store(boost::program_options::command_line_parser(argc, argv).options(desc).run(), configurationVariablesMap); boost::program_options::notify(configurationVariablesMap); if (configurationVariablesMap.count("help")) { std::cout << "Usage: options_description [options]\n"; std::cout << desc; return 0; } } catch(exception& e) { std::cout << e.what() << std::endl; return 1; } Thank you all in advance. Jacques Kerner

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filtered graph
by Matthias Linkenheil 22 Dec '04

22 Dec '04

2 1

multi_index : performance issue
by Stanislas RENAN 22 Dec '04

22 Dec '04

Hi, I've got a performance problem during a test I've done with multi_index on MSVC 6.0 SP 6. I'm using BOOST 1.32.0 . The search performance is comparable with several maps, but insertion is dramatically slow : 5mn 30s for 10 000 employees. Here is my test code : === /* Boost.MultiIndex basic example. * * Copyright 2003-2004 Joaquín M López Muñoz. * Distributed under the Boost Software License, Version 1.0. * (See accompanying file LICENSE_1_0.txt or copy at * http://www.boost.org/LICENSE_1_0.txt) * * See http://www.boost.org/libs/multi_index for library home page. */ #include "stdafx.h" #if !defined(NDEBUG) #define BOOST_MULTI_INDEX_ENABLE_INVARIANT_CHECKING #define BOOST_MULTI_INDEX_ENABLE_SAFE_MODE #endif #include <boost/multi_index_container.hpp> #include <boost/multi_index/member.hpp> #include <boost/multi_index/ordered_index.hpp> #include <algorithm> #include <iostream> #include <iterator> #include <string> #include <cstdlib> #include <map> #include <vector> #include <ctime> #include <sstream> #include <iomanip> using boost::multi_index_container; using namespace boost::multi_index; /* an employee record holds its ID, name and age */ struct employee { int m_id; std::string m_name; int m_age; employee(int id_,const std::string& name_,int age_):m_id(id_),m_name(name_),m_age(age_){} void set(int id_,const std::string& name_,int age_) { m_id=id_; m_name=name_; m_age=age_; } const employee& operator =(const employee& e) { set(e.m_id, e.m_name, e.m_age); return *this; } employee(const employee& e) { set(e.m_id, e.m_name, e.m_age); } int id() const { return m_id; } // impossible d'appeler la fonction et l'index "id" const std::string& name() const { return m_name; } int age() const { return m_age; } friend std::ostream& operator<<(std::ostream& os,const employee& e) { os<<e.m_id<<" "<<e.m_name<<" "<<e.m_age<<std::endl; return os; } }; /* tags for accessing the corresponding indices of employee_set */ struct id{}; struct name{}; struct age{}; /* see Advanced topics: Use of member_offset for info on * BOOST_MULTI_INDEX_MEMBER */ /* Define a multi_index_container of employees with following indices: * - a unique index sorted by employee::int, * - a non-unique index sorted by employee::name, * - a non-unique index sorted by employee::age. */ typedef multi_index_container< employee, indexed_by< ordered_unique< tag<id>, BOOST_MULTI_INDEX_MEMBER(employee,int,m_id)>, ordered_non_unique< tag<name>,BOOST_MULTI_INDEX_MEMBER(employee,std::string,m_name)>, ordered_non_unique< tag<age>, BOOST_MULTI_INDEX_MEMBER(employee,int,m_age)> > > employee_set; template<typename Tag,typename MultiIndexContainer> void print_out_by( const MultiIndexContainer& s, Tag* =0 /* fixes a MSVC++ 6.0 bug with implicit template function parms */ ) { /* obtain a reference to the index tagged by Tag */ const typename boost::multi_index::index<MultiIndexContainer,Tag>::type& i= get<Tag>(s); typedef typename MultiIndexContainer::value_type value_type; /* dump the elements of the index to cout */ std::copy(i.begin(),i.end(),std::ostream_iterator<value_type>(std::cout)); } // Un conteneur qui permet de contenir des employee // triés sur 3 index. class EmployeeMapper { std::map<int, employee *> m_byId; std::map<std::string, employee *> m_byName; std::map<int, employee *> m_byAge; typedef std::map<int, employee *>::iterator EMIdIt; typedef std::map<std::string, employee *>::iterator EMNameIt; typedef std::map<int, employee *>::iterator EMAgeIt; public: EmployeeMapper() {} ~EmployeeMapper() { // Deux lignes pour éviter que ces objets ne contiennent // des pointeurs invalides pendant la destruction va un // autre conteneur. m_byName.clear(); m_byAge.clear(); std::map<int, employee *>::iterator it; while ((it=m_byId.begin()) != m_byId.end()) { delete it->second; m_byId.erase(it); } } void add(const employee& e) { employee * e2 = NULL; try { e2 = new employee(e); } catch(...) { delete e2; throw; } m_byId[e2->id()] = e2; m_byName[e2->name()] = e2; m_byAge[e2->age()] = e2; } employee* byId(int id) { EMIdIt it = m_byId.find(id); if (it == m_byId.end()) return NULL; else return it->second; } employee* byName(const std::string& name) { EMNameIt it = m_byName.find(name); if (it == m_byName.end()) return NULL; else return it->second; } employee* byAge(int age) { EMAgeIt it = m_byAge.find(age); if (it == m_byAge.end()) return NULL; else return it->second; } private: // fonctions inhibées EmployeeMapper(const EmployeeMapper&); const EmployeeMapper& operator=(const EmployeeMapper&); }; // Retourne un entier tq : 0 <= entier < maximum int alea(int maximum) { return int(std::min(maximum, RAND_MAX) * rand() / (RAND_MAX + 1.0)); } int main() { // Init aléatoire srand( (unsigned)time( NULL ) ); employee_set es; EmployeeMapper em; const int tailleEnsemble = 10000; const int tailleEchantillon = 10; const int moduloEchantillon = tailleEnsemble / tailleEchantillon; const int nbRecherches = 10000; std::vector<std::string> noms; noms.push_back("Alphonse"); noms.push_back("Éléonore"); noms.push_back("Gaston"); noms.push_back("Séverine"); noms.push_back("Zorglub"); std::vector<employee> jeuDeDepart; std::vector<employee> jeuARechercher; int i=0; for (i=0; i < tailleEnsemble; ++i) { std::ostringstream os; // Construction d'un nom unique avec un caractère aléatoire // Cela reflète le type de données gérées en réalité. // L'ajout de i implique l'unicité. os << noms[alea(5)] << std::setw(5) << std::setfill('0') << alea(30000) << std::setw(5) << std::setfill('0') << i; employee e(i, // index numérique unique os.str(), // nom, chaîne unique alea(100)); // valeur potentiellement dupliquée jeuDeDepart.push_back(e); // On conserve un échantillon à rechercher plus tard if (0 == i % moduloEchantillon) { //employee_set::iterator it=get<id>(es).find(i); //if (it != es.end()) jeuARechercher.push_back(jeuDeDepart[i]); } } clock_t tes1, tes2; tes1 = clock(); for (i=0; i < tailleEnsemble; ++i) { es.insert(jeuDeDepart[i]); } tes2 = clock(); clock_t tem1, tem2; tem1 = clock(); for (i=0; i < tailleEnsemble; ++i) { em.add(jeuDeDepart[i]); } tem2 = clock(); clock_t t1_1, t2_1; t1_1 = clock(); // Accède à un certain nombre d'éléments précis selon // plusieurs index for (i=0; i < nbRecherches; ++i) { for (std::vector<employee>::iterator it = jeuARechercher.begin(); it != jeuARechercher.end(); ++it) { // Les fonctions membres template qui permette de trouver les // index par tag ne fonctionnent pas avec MSVC 6 employee_set::iterator eit = get<id>(es).find(it->id()); nth_index_iterator<employee_set,1>::type eit2 = get<1>(es).find(it->name()); nth_index_iterator<employee_set,2>::type eit3 = get<2>(es).find(it->age()); } } t2_1 = clock(); clock_t t1_2, t2_2; t1_2 = clock(); // Deuxième méthode : avec des maps et des news. for (i=0; i < nbRecherches; ++i) { for (std::vector<employee>::iterator it = jeuARechercher.begin(); it != jeuARechercher.end(); ++it) { em.byId(it->id()); em.byName(it->name()); em.byAge(it->age()); } } t2_2 = clock(); double d1, d2; d1 = t1_2 - t1_1; d2 = t2_2 - t2_1; std::cout << "Insertion" << std::endl; std::cout << "multi = " << (tes2-tes1) << std::endl << "STL = " << (tem2-tem1) << std::endl; std::cout << "Recherche" << std::endl; std::cout << "multi = " << d1 << std::endl << "STL = " << d2 << std::endl; return 0; } === Here are the results displayed : === Insertion multi = 329125 STL = 156 Recherche multi = 735 STL = 625 === Am I doing something wrong ? Note that I do not instanciate anything explicitely during insertion loop. Regards -- Stanislas RENAN

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Building with Mingw under XP
by Ken Perry 22 Dec '04

22 Dec '04

I am not sure if this has been asked before I tryed searching the archives but there was no search function and a whole bunch of topics. My problem is I am using Mingw under windows xp Pro. I am trying to get the libraries to compile and install in c:\boost which from what I have read is the default directory. when I do bjam --install -sTOOLS=mingw It seems to compile the libraries of corse I think 88 of them fail but it doesn't move the libraries over. What am I doing wrong? Oh one more thing it complains that I don't have python installed at the beginning do I have to have that library because I don't use it in the source I am porting from Linux I just need the boost libraries to get the software ported. Ken

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Re: [Boost-users] boost::serialize on Codewarrior 8.3 (Mac)
by Ryan Wilcox 22 Dec '04

22 Dec '04

On 12/21/04, at 10:09 PM, Ryan Wilcox said: >-----BEGIN PGP SIGNED MESSAGE----- >Hash: SHA1 > > >>--- At Mon, 20 Dec 2004 17:21:11 -0500, Ryan Wilcox wrote: > >>>I would like to use boost::serialize for one of my projects, using >>>Codewarrior 8.3 (going to CW 9 may or may not be in the picture), on >>>Mac OS X (10.3.x) > >I reproduced this error with the following Simplest Sample That Will >(for me) Fail To Compile. [snip] >Part of the error message (the beginning and the end) are still inline >(although just a copy from the OP, it is 999.95% the same as what I get >when I try to compile this sample. Oh wait, no it's not. Same result, differnt path, the header and the footer of the error message are the same, but the body is slighly different. It Might Be Useful to folk, so I've included it again. (somewhat sorry if I violated list policy here) See below: Error : illegal use of abstract class ('boost::archive::detail::basic_iserializer::load_object_data(boost::archive::detail::basic_iarchive &, void *, const unsigned int) const') (point of instantiation: 'main()') (instantiating: 'boost::archive::detail::interface_iarchive<boost::archive::text_iarchive>::operator>><boost::serialization::nvp<std::vector<int, std::allocator<int>>>>(const boost::serialization::nvp<std::vector<int, std::allocator<int>>> &)') (instantiating: 'boost::archive::text_iarchive_impl<boost::archive::text_iarchive>::load_override<boost::serialization::nvp<std::vector<int, std::allocator<int>>>>(boost::serialization::nvp<std::vector<int, std::allocator<int>>> &, int)') (instantiating: 'boost::archive::basic_text_iarchive<boost::archive::text_iarchive>::load_override<boost::serialization::nvp<std::vector<int, std::allocator<int>>>>(boost::serialization::nvp<std::vector<int, std::allocator<int>>> &, int)') (instantiating: 'boost::archive::load<boost::archive::text_iarchive, boost::serialization::nvp<std::vector<int, std::allocator<int>>>>(boost::archive::text_iarchive &, boost::serialization::nvp<std::vector<int, std::allocator<int>>> &)') (instantiating: 'boost::archive::detail::load_non_pointer_type<boost::archive::text_iarchive, boost::serialization::nvp<std::vector<int, std::allocator<int>>>>::invoke(boost::archive::text_iarchive &, boost::serialization::nvp<std::vector<int, std::allocator<int>>> &)') (instantiating: 'boost::archive::detail::load_non_pointer_type<boost::archive::text_iarchive, boost::serialization::nvp<std::vector<int, std::allocator<int>>>>::load_only::invoke(boost::archive::text_iarchive &, boost::serialization::nvp<std::vector<int, std::allocator<int>>> &)') (instantiating: 'boost::serialization::serialize_adl<boost::archive::text_iarchive, boost::serialization::nvp<std::vector<int, std::allocator<int>>>>(boost::archive::text_iarchive &, boost::serialization::nvp<std::vector<int, std::allocator<int>>> &, const unsigned int)') (instantiating: 'boost::serialization::serialize<boost::archive::text_iarchive, boost::serialization::nvp<std::vector<int, std::allocator<int>>>>(boost::archive::text_iarchive &, boost::serialization::nvp<std::vector<int, std::allocator<int>>> &, const unsigned int)') (instantiating: 'boost::serialization::access::serialize<boost::archive::text_iarchive, boost::serialization::nvp<std::vector<int, std::allocator<int>>>>(boost::archive::text_iarchive &, boost::serialization::nvp<std::vector<int, std::allocator<int>>> &, const unsigned int)') (instantiating: 'boost::serialization::nvp<std::vector<int, std::allocator<int>>>::serialize<boost::archive::text_iarchive>(boost::archive::text_iarchive &, const unsigned int) const') (instantiating: 'boost::archive::detail::interface_iarchive<boost::archive::text_iarchive>::operator&<std::vector<int, std::allocator<int>>>(std::vector<int, std::allocator<int>> &)') (instantiating: 'boost::archive::text_iarchive_impl<boost::archive::text_iarchive>::load_override<std::vector<int, std::allocator<int>>>(std::vector<int, std::allocator<int>> &, int)') (instantiating: 'boost::archive::basic_text_iarchive<boost::archive::text_iarchive>::load_override<std::vector<int, std::allocator<int>>>(std::vector<int, std::allocator<int>> &, int)') (instantiating: 'boost::archive::load<boost::archive::text_iarchive, std::vector<int, std::allocator<int>>>(boost::archive::text_iarchive &, std::vector<int, std::allocator<int>> &)') (instantiating: 'boost::archive::detail::load_non_pointer_type<boost::archive::text_iarchive, std::vector<int, std::allocator<int>>>::invoke(boost::archive::text_iarchive &, std::vector<int, std::allocator<int>> &)') (instantiating: 'boost::archive::detail::load_non_pointer_type<boost::archive::text_iarchive, std::vector<int, std::allocator<int>>>::load::invoke(boost::archive::text_iarchive &, std::vector<int, std::allocator<int>> &)') (instantiating: 'boost::archive::detail::iserializer<boost::archive::text_iarchive, std::vector<int, std::allocator<int>>>::instantiate()') iserializer.hpp line 142 static iserializer instance(); Thanks, _Ryan Wilcox

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boost::posix_time::ptime - Parsing time - clarification
by Rakesh Kumar 22 Dec '04

22 Dec '04

Hi, I was going through the API to parse a date-time field. I came across the boost library regarding the same. #include "boost/date_time/posix_time/posix_time.hpp" using namespace boost::posix_time; #include <iostream> #include <cstdlib> using std::cout; int main() { std::string ts("2002-01-20 23:59:59.000"); ptime t(time_from_string(ts)); cout << to_simple_string(t); return EXIT_SUCCESS; } This example compiled fine and gave me the right results. But suppose if I have another date representation as follows. 06 Dec 2004 10:40:58.000 If I enter the same string and try to parse from it, the method time_from_string aborts. I was wondering if there is any way I can tell time_from_string the format and try to parse from it. __________________________________ Do you Yahoo!? Yahoo! Mail - Find what you need with new enhanced search. http://info.mail.yahoo.com/mail_250

2 2

[program_options] option mnemonics
by Joe Higham 21 Dec '04

21 Dec '04

In addition to the ability to define a long and short (one character) name for an option, is there a way to provide an "in-between" name? This way an alias, acronym, or mnemonic version could be provided. For example: desc.add_options() ( "very-long-option-name,vlon,v", value< string >, "a long option name" ) ; and cout << desc would print something like: -v | -vlon | --very-long-option-name arg : a long option name I would also not mind giving up the single-character version in favor of a mnemonic: desc.add_options() ( "very-long-option-name,vlon", value< string >, "a long option name" ) ; cout << desc would print: -vlon [--very-long-option-name] arg : a long option name -- Joe Higham / Blue Sky Studios

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Lambda return type deduction off of the generated lambda fctor (is it possible?)
by Brian Braatz 21 Dec '04

21 Dec '04

I wrote up the simple example that shows what I am trying to figure out Basically, I am trying to pull the deduced return type (or explicitly passed as a template param in lambda bind()) in my template: Any help or direction is greatly appreciated template <typename CURRIEDTYPE> // Id class for currying type without creating the object class Id { public: typedef CURRIEDTYPE TYPE; }; // Explictly pass IN a return type template < typename TFUNCTOR, typename TRET> TRET CallFctorPassInRet ( TFUNCTOR & functor, Id<TRET> & ) { Id<TRET>::TYPE TRet; TRet = functor(); return TRet; } std::string ReturnAString() { return "this is a string"; } // try to get return type from the lambda fctor // Below does not compile- but it is along the lines of what I // WANT to do- note that I am trying to get from the Lambda functor the deduced return type template < typename TFUNCTOR> TFUNCTOR::result_type CallFctorDeduceRet( TFUNCTOR & functor) { return functor(); } void Test_LambdaRetDeduction() { std::cout << "CallFctorPassInRet returns [" << CallFctorPassInRet( bind(&ReturnAString), Id<std::string>()) << "]" << std::endl; // below is what I want to make work std::cout << "CallFctorDeduceRet returns [" << CallFctorDeduceRet( bind<std::string>(&ReturnAString)) << "]" << std::endl; }

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Class template spec with enable_if
by Agoston Bejo 21 Dec '04

21 Dec '04

Hello again! See the example below. (Platform: VC++7.1) This error is strange for me because it only occurs in the case of class template specialization. The compiler deduces the type of is_arithmetic<T>::value falsely, not as bool, althought it is known at compile time, isn't it? The error messages (both referring to the erroneous line marked with "ERROR"): error C2296: '&&' : illegal, left operand has type 'is_arithmetic<T>::value' error C2297: '&&' : illegal, right operand has type 'is_arithmetic<T2>::value' Thx, Agoston Example: //------------------------------------------------------- #include <iostream> #include <boost/utility/enable_if.hpp> #include <boost/type_traits.hpp> #include <boost/mpl/and.hpp> using namespace std; using namespace boost; using namespace mpl; // ----------------- template<typename T1, typename T2, typename TEnabler = void> struct Enabler { static const bool value = false; }; template<typename T1, typename T2> struct Enabler<T1, T2, typename enable_if_c< is_arithmetic<T1>::value && is_arithmetic<T2>::value >::type // ERROR!!! > { static const bool value = true; }; */ /* //WOULD WORK: typename enable_if< and_< is_arithmetic<T1>, is_arithmetic<T2> > >::type */ // ----------------- template<typename T1, typename T2> typename enable_if_c< is_arithmetic<T1>::value && is_arithmetic<T2>::value >::type f(T1 t1, T2 t2) { cout << t1 << " " << t2 << endl; } // ----------------- int _tmain(int argc, _TCHAR* argv[]) { f(5.0, 6); return 0; }

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