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Spirit Attributes, Semantic Actions, and Closures: The relationship.
by Aaron W. LaFramboise 14 Jun '04

14 Jun '04

Hi, I've been learning about Boost Spirit from the documentation, and one big gap I'm finding is how Spirit knows to call a particular signature semantic action given a particular parser. I see this has something to do with the match type, but I'm not sure how to actually define the match type for rule. I've discovered by accident that semantic actions seem to be called with the type of the closure member of a single-member closure, but I don't see this documented, and I can't quite figure out how its supposed to work. Its difficult to deduce expected signatures by the compiler error approach because GCC is giving fairly nonsensical errors for the sorts of template constructs Spirit seems to use, when something goes wrong. In particular, I'd like to know specifically how I am supposed to be defining semantic actions for my rules. Perhaps this is something that would be nice to be included somewhere in the documenation. Maybe it is, but I missed it somehow, or it wasn't spelled out explicitly enough for me to catch on. Any help or pointers would be greatly appreciated! (By the way, I have to repeat the almost obligatory comment that everyone seems to make about Spirit: it is one of the most beautiful examples of C++ I have ever seen!) Aaron W. LaFramboise

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boost::random dynamically select generator
by Bo Peng 14 Jun '04

14 Jun '04

Dear List, I am using the following (typical) code to use boost::random --------------------------------------------- typedef boost::mt19937 generator_type; typedef boost::variate_generator<generator_type&, boost::uniform_real<double> > rand01Generator; generator_type random_gen; boost::uniform_real<double> distrib(0.0, 1.0); rand01Generator rand01(random_gen, distrib); ---------------------------------------------- I would like to give users the ability to choose random number generators through something like: // global generator that is being used everywhere generator global_generator; void setGenerator(string type) { if(type == "mt19937") global_generator = ... ... } However, the generators are templates so the type of global generator can not be specified. Is there any workaround? It seems that a wrapper class with instances of all available generators and some if-else code can do this but there should be better ideas. Many thanks in advance. Bo

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RE: [Boost-users] problems using shared_ptr in threads
by Ben Hutchings 13 Jun '04

13 Jun '04

Tristan King <tristanking(a)internode.on.net> wrote: > Hi, > I'm having trouble getting shared_ptr objects and threads to work in > harmony. <snip> > i'm not worried about the order that the threads run in (as this is > just an example of the problem i'm having in a simple multi-threaded > web server i'm working on), but it seems like the shared_ptr object > may be getting deleted before the last thread gets to execute. Yes, that is what is happening. The problem is that your single_thread objects are destroyed at the end of the loop body. By the time the new thread runs its single_thread may have been destroyed along with all its members. Since each single_thread is constructed in the same block of memory, it is possible for the thread to pick up the value intended for the next thread. <snip> > can anyone give me any pointers on how to get around this problem? <snip> I suggest you create your thread objects with 'new' instead, or else define an array of them outside the loop. Ben.

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enable_if question
by Agoston Bejo 13 Jun '04

13 Jun '04

Hi, I understand that by using enable_if the following way: template <class T> T foo(T t, typename enable_if<boost::is_arithmetic<T> >::type* dummy = 0); I can include/exclude the appropriate function overloads. When I write: template<class T> T foo(T t, typename enable_if<[condition1]>::type* dummy = 0, typename enable_if<[condition2]>::type* dummy = 0); Does this mean an AND-relationship between condition1 and condition2? (So that a particular overload is enabled if and only if both conditions evaluate to true?) Thx, Gus

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Dynamic bitset help
by Michael Short 13 Jun '04

13 Jun '04

Hello Has anyone got a few good examples of the dynamic bitset been used with member functions like append and block type? If so could you please send in some thanks. Michael

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regex v4: regex_replace fails on trivial case
by Watermann Bernd (TCO/A) 12 Jun '04

12 Jun '04

Hi all, regex_replace("XX",regex("X", boost::regex::literal), "Y") returns "YXY" instead of "YY" whereas the (even more) trivial case regex_replace("X",regex("X", boost::regex::literal), "Y") returns "Y" as expected. I am using boost_1_31_0 compiled with VC6(SP5). In addition, I have applied the patches from the package boost-1.31.0-regex-patch-20040503. What is going wrong here? Bernd

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newbie question: missing libs ?
by Randy.Ormond＠ngc.com 11 Jun '04

11 Jun '04

After building Boost 1.31.0 on Linux and on Irix, I expected to see a smart pointer library, something like libboost_smart_ptr-gcc-mt.so If fact, it looks like only date_time, filesystem, prg_exec, regex, signals, test_exec_monitor, thread, and unit_test_framework were built. I didn't see any error messages. Did I do something wrong? Thanks, Randy

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Additional boost resources
by Agoston Bejo 11 Jun '04

11 Jun '04

Hi, do you know about any additional books, tutorials, etc. about boost on the net apart from the boost documentation itself? Any links / titles are welcome. Thx, Gus

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problems using shared_ptr in threads
by Tristan King 11 Jun '04

11 Jun '04

Hi, I'm having trouble getting shared_ptr objects and threads to work in harmony. It may just be that i don't know enough about threads to solve this, but i'm getting undefined behaviour in the code posted at the end of this mail. i'm not worried about the order that the threads run in (as this is just an example of the problem i'm having in a simple multi-threaded web server i'm working on), but it seems like the shared_ptr object may be getting deleted before the last thread gets to execute. i.e. some sample output i'm getting is 0 1 3 4 -572662307 and 1 2 3 3 -572662307 i think i'm probably missing some mutex's or something, but i can't figure it out can anyone give me any pointers on how to get around this problem? thanks in advance --Tristan #include <iostream> #ifdef _MSC_VER #pragma warning(push, 1) #endif #include <boost/thread.hpp> #include <boost/shared_ptr.hpp> #ifdef _MSC_VER #pragma warning(pop) #endif struct simple_thread : public boost::noncopyable { simple_thread( boost::shared_ptr<int> i ) : m_i( i ) {} void operator( )( ) { std::cout << (*m_i) << std::endl; } boost::shared_ptr<int> m_i; }; int main( ) { boost::thread_group threads; for ( int i = 0 ; i < 5 ; ++i ) { boost::shared_ptr<int> p( new int(i) ); simple_thread trd( p ); threads.create_thread( boost::ref( trd ) ); }; threads.join_all( ); return 0; }

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link problems with boost_regex on Solaris
by Drew Lowry 09 Jun '04

09 Jun '04

I'm using boost_regex 1.28.0 with STLport 4.5.3 on Solaris using Forte compiler. When I build with -g option, it fails at linkage with the following errors ild: (undefined symbol) boost::detail::allocator<unsigned char>::allocator<char>#Nvariant 1(const boost::detail::allocator<__type_1>&) -- referenced in the text segment of ../../../../packages/boost_1_28_0/sparc-solaris/libboost_regex_mt.a(OhCenAP7d5aN-_Bfr3wh.o) ild: (undefined symbol) boost::detail::allocator<unsigned char>::allocator<char>#Nvariant 1(const boost::detail::allocator<__type_1>&) -- referenced in the text segment of ../../../../packages/boost_1_28_0/sparc-solaris/libboost_regex_mt.a(J-U5NXbbfexb9iPLelyN.o) ild: (undefined symbol) boost::detail::allocator<unsigned char>::allocator<char>#Nvariant 1(const boost::detail::allocator<__type_1>&) -- referenced in the text segment of ../../../../packages/boost_1_28_0/sparc-solaris/libboost_regex_mt.a(5cVinizdRsfQ1ujqbKlp.o) ild: (undefined symbol) boost::detail::allocator<unsigned char>::allocator<char>#Nvariant 1(const boost::detail::allocator<__type_1>&) -- referenced in the text segment of ../../../../packages/boost_1_28_0/sparc-solaris/libboost_regex_mt.a(TbU7jVI0o3rCSz-c48HV.o) ild: (undefined symbol) boost::detail::allocator<unsigned char>::allocator<char>#Nvariant 1(const boost::detail::allocator<__type_1>&) -- referenced in the text segment of ../../../../packages/boost_1_28_0/sparc-solaris/libboost_regex_mt.a(Zi2bUcR97vUxCHzFzV0a.o) ild: (undefined symbol) boost::detail::allocator<unsigned char>::allocator<char>#Nvariant 1(const boost::detail::allocator<__type_1>&) -- referenced in the text segment of ../../../../packages/boost_1_28_0/sparc-solaris/libboost_regex_mt.a(aTM7t-gA2lwhiyP5RH3P.o) ild: (undefined symbol) boost::detail::allocator<unsigned char>::allocator<char>#Nvariant 1(const boost::detail::allocator<__type_1>&) -- referenced in the text segment of ../../../../packages/boost_1_28_0/sparc-solaris/libboost_regex_mt.a(OkRWOOTWnnv97gH0a9t_.o) ild: (undefined symbol) boost::detail::allocator<unsigned char>::allocator<char>#Nvariant 1(const boost::detail::allocator<__type_1>&) -- referenced in the text segment of ../../../../packages/boost_1_28_0/sparc-solaris/libboost_regex_mt.a(hKZggW9H89qzPd1td_2e.o) ild: (undefined symbol) boost::detail::allocator<unsigned char>::allocator<char>#Nvariant 1(const boost::detail::allocator<__type_1>&) -- referenced in the text segment of ../../../engine/lib/sparc-solaris/ Any idea what's going on? Everything works fine without -g option. ____________________________________________________________ Yahoo! Messenger - Communicate instantly..."Ping" your friends today! Download Messenger Now http://uk.messenger.yahoo.com/download/index.html

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