May 2008 - Boost-users - lists.boost.org

Somewhat off-topic: Any equivalent to Python's "Beautiful Soup" for C++
by Daniel Lord 20 May '08

20 May '08

Beautiful Soup, for anyone who doesn't know, is a highly-tolerant HTML parser that is great for screen-scraping non-compliant (as well as compliant) HTML ( http://www.crummy.com/software/BeautifulSoup/ ). Although I've often resorted to using PyObjC on OS X to allow me to leverage Python's rich high-level modules from ObjC and C++, there are times when I don't want to use Python past the prototyping stage because of performance issues. But powerful modules like Beautiful Soup are then sorely missed. Anyone know of a similar library for C++? Daniel Lord

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64-bit Boost 1.35.0 Python 2.5 Related Questions
by Eric Newhuis 20 May '08

20 May '08

[Boost.Python] Has anyone successfully built and run a 64-bit Python 2.5 extension module? I am using 64-bit RedHat Linux and I have encountered a number of oddities including segfaults doing simple things like evaluating the keys of a dict from c++. Does anyone have a sequence of steps they used to produce a working extension module with this configuration that they'd like the share? I am interested from the point of configuring and installing boost all the way through the Jamfile for the extension module. Formerly everything worked fine using 1.34.

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[value_initialized] Non-default constructors
by Edward Diener 20 May '08

20 May '08

I have a class template, templated on type T, which I need to hold as a data value in the class. I use value_initialized for this type T effectively, and the value gets value initialized correctly when the default constructor of my class is used. If, however, I add a second constructor to my class which takes a T, for initializing my 'value_initialized<T> data' value, things do not work as well. Obviously I can still value initialize my data value, as in my default constructor, and then use 'boost::get(data) = arg;' to set the value of my value initialized variable. But this will not work if the type T is a top-level const, whereas I do want to initialize the data value in this case to the T arg passed into my second constructor. Is there a good solution to this which I have overlooked ?

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Re: [Boost-users] Boost serialization: how to register template derivedclass
by Lifshitz, Yair 20 May '08

20 May '08

Hi, I hope what I'm saying here makes sense and won't be considered flooding. While trying to check the reason for BOOST_CLASS_EXPORT not working with templates, I found out the problem is simply a preprocessor issue - it treats each comma as a seperation between values, so it treats a template (as below) as two inputs (and the MACRO accepts only one). We implemented BOOST_CLASS_EXPORT_WITH_TWO_VALS, and it worked fine with the template argument below, saving us the need to expand the macro for each instantiation. Is there anything we're missing here? Is support for this planned in future Boost releases? Thanks for your time, Yair Lifshitz Intel Israel ----- Forwarded Message ---- From: Robert Ramey <ramey(a)rrsd.com> To: boost-users(a)lists.boost.org Sent: Thursday, May 8, 2008 7:49:08 AM Subject: Re: [Boost-users] Boost serialization: how to register template derivedclass what you would really need is something like BOOST_CLASS_EXPORT(KukuBase<int, 5>); BUT the the shorthand macro BOOST_CLASS_EXPORT doesn't like template instantiations so you'll have to expand the macro "by hand" for the class for each set of template parameters used. This is explained in the manual. Robert Ramey "ari vol" <avf99avf(a)yahoo.com> wrote in message news:9202.25698.qm@web45110.mail.sp1.yahoo.com... Hey, Boost serialization <http://www.boost.org/doc/libs/1_35_0/libs/serialization/doc/index.html> : how to register template derived class. The problem in general: I have the following classes: - Virtual based class: class TemplateBase { } - Derived class: template <class KUKU, int KUKUINT> class KukuBase : public TemplateBase{ } And I am trying to serialize the derived class KukuBase<KUKU, KUKUINT> through a pointer of the base type (polymorphism...). The problem is that I can not find a way to register the class KukuBase<KUKU, KUKUINT> and thus get unregistered_class <http://us.mg3.mail.yahoo.com/dc/exceptions.html> exception. How to make it works? The cpp file: #include <boost/archive/text_oarchive.hpp> #include <boost/archive/text_iarchive.hpp> // Serialization #include <boost/serialization/string.hpp> #include <boost/serialization/vector.hpp> #include <boost/serialization/access.hpp> #include <boost/serialization/base_object.hpp> #include <boost/serialization/serialization.hpp> #include <boost/serialization/export.hpp> #include <fstream> class TemplateBase { public: TemplateBase() : mI(0) {} virtual TemplateBase* Clone() = 0; int mI; private: friend class boost::serialization::access; template<class Archive> void serialize(Archive & ar, const unsigned int version) { ar & mI; } }; template <class KUKU, int KUKUINT> class KukuBase : public TemplateBase { public: KukuBase() : mZ(1) {} TemplateBase* Clone() { return new KukuBase<KUKU, KUKUINT>(*this); } private: friend class boost::serialization::access; template<class Archive> void serialize(Archive & ar, const unsigned int version) { ar & boost::serialization::base_object<TemplateBase>(*this); ar & mZ; } float mZ; }; class foo { public: foo() : mT(new KukuBase<int, 5>) {}; template<class Archive> void serialize(Archive & ar, const unsigned int version) { ar & mT; } TemplateBase* mT; }; BOOST_CLASS_EXPORT(foo); //BOOST_CLASS_EXPORT((KukuBase)); BOOST_CLASS_EXPORT(TemplateBase); int main() { std::ofstream ofs("/tmp/kuku"); boost::archive::text_oarchive ar(ofs); const foo bar; ar << bar; } The program returns: terminate called after throwing an instance of 'boost::archive::archive_exception' what(): unregistered class Abort And the stuck shows: (gdb) bt #0 0x000000000049e409 in kill () #1 0x0000000000470582 in abort () at ../sysdeps/generic/abort.c:88 #2 0x0000000000461bf8 in __gnu_cxx::__verbose_terminate_handler () #3 0x000000000045e216 in __cxxabiv1::__terminate () #4 0x000000000045e243 in std::terminate () #5 0x000000000045e343 in __cxa_throw () #6 0x000000000040190c in boost::throw_exception<boost::archive::archive_exception> () #7 0x00000000004015e1 in boost::archive::detail::save_pointer_type<boost::archive::text_oarchive, TemplateBase*>::polymorphic<TemplateBase>::save () #8 0x000000000040152d in boost::archive::detail::save_pointer_type<boost::archive::text_oarchive, TemplateBase*>::save<TemplateBase> () #9 0x000000000040142e in boost::archive::detail::save_pointer_type<boost::archive::text_oarchive, TemplateBase*>::invoke () #10 0x00000000004013aa in boost::archive::save<boost::archive::text_oarchive, TemplateBase*> () #11 0x0000000000401344 in boost::archive::basic_text_oarchive<boost::archive::text_oarchive>::save _override<TemplateBase* const> () #12 0x00000000004012e8 in boost::archive::detail::interface_oarchive<boost::archive::text_oarchive >::operator<< <TemplateBase* const> () #13 0x0000000000401299 in boost::archive::detail::interface_oarchive<boost::archive::text_oarchive >::operator&<TemplateBase*> () #14 0x000000000040124c in foo::serialize<boost::archive::text_oarchive> () #15 0x0000000000401197 in boost::serialization::access::serialize<boost::archive::text_oarchive, foo> () #16 0x0000000000401107 in boost::serialization::serialize<boost::archive::text_oarchive, foo> () #17 0x0000000000400f83 in boost::serialization::serialize_adl<boost::archive::text_oarchive, foo> () #18 0x00000000004022c6 in boost::archive::detail::oserializer<boost::archive::text_oarchive, foo>::save_object_data () #19 0x0000000000405c59 in boost::archive::detail::basic_oarchive_impl::save_object () #20 0x0000000000400d43 in boost::archive::detail::save_non_pointer_type<boost::archive::text_oarch ive, foo>::save_standard::invoke () #21 0x0000000000400c6f in boost::archive::detail::save_non_pointer_type<boost::archive::text_oarch ive, foo>::invoke () #22 0x0000000000400aff in boost::archive::save<boost::archive::text_oarchive, foo> () #23 0x0000000000400a38 in boost::archive::basic_text_oarchive<boost::archive::text_oarchive>::save _override<foo const> () #24 0x000000000040090e in boost::archive::detail::interface_oarchive<boost::archive::text_oarchive >::operator<< <foo const> () #25 0x0000000000400423 in main () (gdb) Quit Thanks, -Ariella ________________________________ From: Voloshin, Ariella Sent: Tuesday, May 20, 2008 11:10 AM To: Lifshitz, Yair Subject: RE: Hey Yes I will use it, I guess you will need to register the: boost-users(a)lists.boost.org. The guy that wrote the boost serialization library is Robert Ramey ramey(a)rrsd.com. If you like to answer from my email thread please let me know. ________________________________ From: Lifshitz, Yair Sent: Friday, May 16, 2008 8:55 AM To: Voloshin, Ariella Cc: Lifshitz, Yair Subject: RE: Hey Great! :) So I hope you're going to use it. Can you send me the Boost owner's mail - I want to have a look and maybe have a chat with him. ________________________________ From: Voloshin, Ariella Sent: Thursday, May 15, 2008 11:01 PM To: Lifshitz, Yair Subject: Hey It is working, Took some time to compile, long story but it is working. The string is also ok. Thanks, -Ariella --------------------------------------------------------------------- Intel Israel (74) Limited This e-mail and any attachments may contain confidential material for the sole use of the intended recipient(s). Any review or distribution by others is strictly prohibited. If you are not the intended recipient, please contact the sender and delete all copies.

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[Regex] How to use BOOST_REGEX_RECURSIVE
by Richard Hadsell 20 May '08

20 May '08

I just discovered the Regex algorithm selection macros that have been around for a long time. I noticed that BOOST_REGEX_RECURSIVE is supposed to enable a faster algorithm, and it is not the default on Linux systems. Most of our patterns are very simple, so I am not worried about pathological cases, and I would like to try the recursive algorithm. Do I need to modify boost/regex/user.hpp before building the library? Do I need to compile my applications with the macro defined as a compiler option? Is it sufficient to define the macro in a source file before including the boost/regex.h header? -- Dick Hadsell 914-259-6320 Fax: 914-259-6499 Reply-to: hadsell(a)blueskystudios.com Blue Sky Studios http://www.blueskystudios.com 44 South Broadway, White Plains, NY 10601

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Could two boost threads with the same name run at the same time?
by he xiang 20 May '08

20 May '08

Hi, all， My code looks like this: ============================================================= // M is a class, m_show() is one of its methods. void test_boost_thread_1(){ M p(88); boost::thread pthd(boost::bind(&M::m_show, &p)); } void test_boost_thread_2(){ M p(99); boost::thread pthd(boost::bind(&M::m_show, &p)); } =============================================================== "test_boost_thread_1()" and "test_boost_thread_2()" are running at the same time ,but I find that the output is wrong. If I changed the thread name "pthd" in "test_boost_thread_()" to other name , not "pthd" , it looks ok. why ? ........ Now , many other threads want to run " test_boost_thread_1() " at the "same" time, How could I make it ok ? Thanks for your time. Best Regards.

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mpl for_each copies function object (bug?)
by Sebastian Weber 20 May '08

20 May '08

Hi there! I'm currently struggling with mpl::for_each: It copies my function object no matter what I do. Here is some dummy code: worker_t workit; // the worker object which recieves the different types and has an internal state mpl::for_each< mpl::vector<bool, double>, worker_t& >(workit); Now, the workit object becomes copied which is clear from the sources. However, I explicitly requested it not to be copied by the hint of giving the reference worker_t& as a template parameter. Maybe this behaviour is wanted, but I do not see the reason. In the fusion-world this is the way to go if one wants to prevent copying of function objects. Is this now a bug or a feature and how can I fix it (quick). Greetings, Sebastian

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compiling boost on IBM AIX: gcc or xlC?
by Andrej van der Zee 20 May '08

20 May '08

Hi, I am new to IBM AIX but have a project assigned to me that requires me to compile boost on AIX 5.3. I was wondering if I should use gcc or xlC. I prefer the former since I am familiar with it. Does anybody has experience and/or tips? Cheers, Andrej __________________________________________________________ Sent from Yahoo! Mail. A Smarter Email http://uk.docs.yahoo.com/nowyoucan.html

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Lambda and Fusion: result_of problems
by Anders Sundman 20 May '08

20 May '08

Hi! After recently discovering the the Fusion library I've been playing around with it for a bit. It's pretty awesome. There is however one thing I haven't been able to figure out. How do you use it with lambda expressions? E.g. t1 & t1 are tuples of doubles fusion::transform(t1, t2, std::minus<double>()) // Works fine fusion::transform(t1, t2, lambda::_1 - lambda::_2) // Doesn't work I'm not sure I understand the problem correctly, but it seems to be related to boost::result_of. For some reason the lambda functor doesn't seem to define it's return type (F::template result<FArgs>)? Am I doing something wrong or is this a known awkwardness? If so, are there any convenient workarounds? Best Regards, Anders Sundman

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hash set crashing during iteration (boost 1.35.0)
by Julie Larson 20 May '08

20 May '08

Hello, I'm using boost 1.35.0 and found this sample code about the hash set functionality: http://www.boost.org/doc/libs/1_35_0/doc/html/intrusive/advanced_lookups_in… and modified it as shown below. I find that when iterating through the hash table, the thing crashes here (where the get_next function contains an invalid value for n): template<class VoidPointer> struct slist_node_traits { .... static node_ptr get_next(const_node_ptr n) ----------> { return n->next_; } .... }; Should I use an earlier more stable version of boost or am I doing something dreadfully wrong? Thank you for any insights -Julie #include <stdio.h> #include <string> #include <iostream> // for std::cout #include <boost/foreach.hpp> #include <boost/intrusive/unordered_set.hpp> using namespace boost::intrusive; struct CStringHasher { std::size_t operator()(const std::string& str) const { std::size_t seed = 0; const char* sz = str.c_str(); if ( ! sz ) return seed; for(; *sz; ++sz) boost::hash_combine(seed, *sz); return seed; } }; class CWord : public unordered_set_base_hook<> { //This is a derivation hook public: std::string m_strWord; int m_nID; unordered_set_member_hook<> member_hook_; //This is a member hook CWord( const std::string& strWord, int nID ) : m_strWord( strWord ), m_nID( nID ) {} friend bool operator== (const CWord& a, const CWord& b) { return a.m_strWord == b.m_strWord; } friend std::size_t hash_value(const CWord& value) { return CStringHasher()(value.m_strWord.c_str()); } }; class CWordHash { public: typedef unordered_set<CWord> word_hash_set; typedef word_hash_set::bucket_type word_bucket_type; typedef word_hash_set::bucket_traits word_bucket_traits; typedef word_hash_set::iterator word_iter; CWordHash() : m_hWords( word_bucket_traits( m_Buckets, s_nNumBuckets ) ) {} ~CWordHash() { BOOST_FOREACH( CWord& w, m_hWords ) { CWord* pWord = &w; delete pWord; } } struct CStrExpensiveClassEqual { bool operator()(const std::string& str, const CWord &c) const { return str == c.m_strWord; } bool operator()(const CWord& c, const std::string& str) const { return str == c.m_strWord; } }; CWord* get( const std::string& str ) { word_iter it = m_hWords.find( str, CStringHasher(), CStrExpensiveClassEqual()); if( it == m_hWords.end() ) return NULL; return &*it; } bool insert( const std::string& strKey, int nID ) { word_hash_set::insert_commit_data insert_data; bool bSuccess = m_hWords.insert_check( strKey, CStringHasher(), CStrExpensiveClassEqual(), insert_data).second; if ( bSuccess ) { CWord* pWord = new CWord(strKey, nID); m_hWords.insert_commit(*pWord, insert_data); } return bSuccess; } static const int s_nNumBuckets = 10000; word_bucket_type m_Buckets[s_nNumBuckets]; word_hash_set m_hWords; }; extern int main(int argc, char *argv[]) { CWordHash hWords; // hash string to word id int nID = 1; std::string strWord = "hello"; hWords.insert( strWord, nID ); nID = 2; strWord = "world"; hWords.insert( strWord, nID ); for ( CWordHash::word_hash_set::iterator it = hWords.m_hWords.begin(); it != hWords.m_hWords.end(); it++ ) { CWord& w = *it; std::cout << w.m_strWord << "\t" << w.m_nID << "\n"; } return 0; }

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