March 2005 - Boost-users - lists.preview.boost.org

[wiki] New content filtering to reduce spam
by Jeff Garland 14 Mar '05

14 Mar '05

All - I've instituted a new content filter on the Wiki to try and cut off the spamming without going to a login or other user intrusive mechanism. The timing of this feature turned out to be important as a sophisticated spambot that evades the ip banning strategy by using many different ip addresses (presumably using zombie machines) has been attempting to SPAM the wiki all day today. The new content filter has sucessfully stopped this bot. Note that if a spammer is successful I am now reverting all spam content from the Wiki history so that there is no chance of googlebot finding it. For the moment, I'm not going to publish the regular expressions I'm using to filter, but suffice to say, normal boost content should be unaffected. If you get an error indicating content has been blocked due to spam, send me and email. Thanks, Jeff

1 0

How does Boost.Build/bjam find boost?
by Kelly Burkhart 13 Mar '05

13 Mar '05

Hello, I am starting to fiddle with boost and bjam and am not able to get bjam to find the boost headers and libraries. I'm running SuSE 9.1 and started out using the RPMs. Since last night, one-by-one I've uninstalled the RPMs and replaced with freshly downloaded and build components. Right now I have the latest boost,bjam and boost.build releases. I built boost with --prefix=/opt/boost and installed it. I have boost.build placed in /opt/boost as well. Under my home directory I have a directory in which I'm trying to build a hello-world program. The directory contents: > ls boost-build.jam Jamfile project-root.jam tst.cpp > cat boost-build.jam boost-build /opt/boost/boost-build ; > cat Jamfile exe tst : tst.cpp ; > cat tst.cpp #include <iostream> #include <string> #include "boost/format.hpp" int main() { std::cout << boost::format("%1%, world") % "hello" << std::endl; return 0; } project-root.jam is empty. When I try to build with 'bjam tst' it is not able to find the boost headers, which makes sense, because I've not been able to figure out how to indicate where they live. How is this accomplished? -K

3 9

Boost::regex: Removing Forte CC compiler warnings
by Rajesh Radhakrishnan 13 Mar '05

13 Mar '05

Hi, Any suggestions on removing these compiler warnings (CC: Sun C++ 5.5 2003/03/12 ) : /usr/local/boost_regex/include/boost/type_traits/is_convertible.hpp", line 279: Warning (Anachronism): Type names qualified by template parameters require "typename". "/usr/local/boost_regex/include/boost/type_traits/is_convertible.hpp", line 279: Where: While specializing "boost::is_convertible<boost::From, boost::To>". "/usr/local/boost_regex/include/boost/type_traits/is_convertible.hpp", line 279: Where: Specialized in non-template code. "/usr/local/boost_regex/include/boost/type_traits/is_convertible.hpp", line 279: Warning (Anachronism): Type names qualified by template parameters require "typename". "/usr/local/boost_regex/include/boost/type_traits/is_convertible.hpp", line 279: Where: While specializing "boost::is_convertible<boost::From, boost::To>". "/usr/local/boost_regex/include/boost/type_traits/is_convertible.hpp", line 279: Where: Specialized in non-template code. Line 279: /usr/local/boost_regex/include/boost/type_traits/is_convertible.hpp BOOST_TT_AUX_BOOL_TRAIT_DEF2(is_convertible,From,To,(::boost::detail::is_convertible_impl<From,To>::value)) -- Regards Rajesh

2 1

MPL - creating new sequence from another sequence using predicate
by Bruce Trask 13 Mar '05

13 Mar '05

Hi, I have a mpl::vector of types. Each of the types in the vector have themselves another nested mpl::vector that is a sequence of enums. I have include the code below. What I am trying to do is take the original sequence and make a new sequence based on the predicate that only elements with certains enums in their nested vector be included in the new sequence. I have included more notes in the embedded comments. I was thinking of using mpl::copy_if but am having trouble getting the predicate right. Wanted to know if anyone could steer me in the right direction. I am trying to fill in the ??? below. I am having trouble writing a custom predicate. Thanks in advance. Regards, Bruce #include <string> #include <iostream> #include <boost/mpl/vector.hpp> #include <boost/mpl/begin_end.hpp> #include <boost/mpl/deref.hpp> #include <boost/mpl/count_if.hpp> #include <boost/mpl/size.hpp> #include <boost/mpl/for_each.hpp> #include <boost/type_traits/is_member_pointer.hpp> #include <boost/mpl/vector_c.hpp> #include <boost/mpl/copy_if.hpp> #include <boost/mpl/less.hpp> #include <boost/mpl/placeholders.hpp> #include <boost/mpl/find.hpp> namespace mpl = boost::mpl; using namespace mpl::placeholders; enum colors { red, blue, green, yellow }; template<typename COLORTYPES> struct TestClass { typedef COLORTYPES colortypes; }; void func() { // come up with a interface to simplify this like vector_c - only it must be able to handle enums - I would think one would already exist typedef mpl::vector< mpl::integral_c<colors,red> , mpl::integral_c<colors,green> , mpl::integral_c<colors,blue> > colorcoll1; typedef mpl::vector< mpl::integral_c<colors,red> , mpl::integral_c<colors,blue> > colorcoll2; typedef mpl::vector< mpl::integral_c<colors,green> > colorcoll3; typedef mpl::vector<TestClass<colorcoll1>, TestClass<colorcoll2>, TestClass<colorcoll3> > testvector; std::cout << " SIZE IS " << mpl::size<testvector>::value << std::endl; // would like to make a new vector from testvector that contains only those types that have green in their nested vector colortypes. //In other words, go from testvector which has three types to a vector that only has TestClass<colorcoll1> and TestClass<colorcoll3> // typedef mpl::copy_if<testvector, ???? >::type testvectorwithgreen; // I can do it successfully when operating directly on the container as below, but am having trouble deterimining the predicate for the above case typedef mpl::vector_c<int, 1,2,3,4,5,6,7,8> intColl; std::cout << mpl::size<intColl>::value << std::endl; typedef mpl::copy_if<intColl, mpl::less<mpl::_1, mpl::int_<5> > >::type newIntColl; std::cout << mpl::size<newIntColl>::value << std::endl; } int main() { func(); return 0; }

3 4

boost::fsm, parameters to DestinationState
by Jan Eickmann 12 Mar '05

12 Mar '05

Hi, when doing a transition using transit<myDestinationState>, I would like to pass some parameters to myDestination. Problem is, those parameter-values will not be known at compile time, so I can't just pass them in as template-parameters to myDestinationState. Of course I could just set some global (or static member member) variable and read that from myDestinationState's constructor but this doesn't feel like a very clean design. Any suggestions? Jan Eickmann

2 6

base64->wstring decoding
by Stefan Strasser 12 Mar '05

12 Mar '05

Hi, I need to write a std::wstring which can contain binary data like \0 to a xml attribute, so I'm converting it to base64 but I have problems decoding it: typedef transform_width<binary_from_base64<std::string::const_iterator>,32,6> decode; std::wostringstream out; std::copy(decode(in.begin()),decode(in.end()),std::ostream_iterator<wchar_t,wchar_t>(out)); is this a correct way to decode base64? it works, but only if (bits % 6 == 0). otherwise the program is abort()ed due to an exception. the string was encoded by base64_from_binary<transform_width<std::wstring::const_iterator,6,32> > Thanks, -- Stefan Strasser

2 2

question on using BOOST_FOREACH with non-stl container
by Michael W Daniels 12 Mar '05

12 Mar '05

In experimenting with the new BOOST_FOREACH header, I'm getting the compile error (MSVC 7.1) below with this code. The documentation for BOOST_FOREACH says: >The support for STL containers is very general; anything that looks like >an STL container counts. If it has nested iterator and const_iterator >types and begin() and end() member functions, BOOST_FOREACH will >automatically know how to iterate over it. I've checked, and the hashed_array_tree class does have nested iterator and const_iterator types, as well as begin() and end() member functions. (It's originally from www.cphstl.dk, but that site no longer provides the code.) Replacing hashed_array_tree with vector gets rid of the error, so there's obviously something I need to fix in the hashed_array_tree. How do I figure out what that is, though? Any help will be greatly appreciated. ===code=== #include <memory> #include <iostream> #include "foreach.hpp" #include "math_utils.hpp" #include "hashed_array_tree.hpp" #include "hat_iterator.hpp" using namespace std; using namespace boost; using namespace cphstl; class A { public: int foo; }; void test() { const hashed_array_tree<const A*>* Ahat = new hashed_array_tree<const A*>(); BOOST_FOREACH(const A* curA, *Ahat) cout << curA->foo; } ====== ==error== e:\Projects\gidlp\fsparser\foreach.hpp(455) : error C2440: 'return' : cannot convert from 'const std::allocator<_Ty>::value_type' to 'boost::iterator_reference<Iterator>::type' with [ _Ty=const A * ] and [ Iterator=boost::range_const_iterator<cphstl::hashed_array_tree<const A *>>::type ] Conversion loses qualifiers e:\Projects\gidlp\fsparser\test2.cpp(20) : see reference to function template instantiation 'boost::iterator_reference<Iterator>::type boost::for_each::deref<cphstl::hashed_array_tree<T>,boost::mpl::true_>(boost::for_each::static_any_t,boost::for_each::container<cphstl::hashed_array_tree<T>,C>)' being compiled with [ Iterator=boost::range_const_iterator<cphstl::hashed_array_tree<const A *>>::type, T=const A *, C=boost::mpl::true_ ] ====== -- Michael W. Daniels | Choreography is its own reward. daniels(a)ling.osu.edu | Some things are done only for the sake Doctoral Candidate | of form. Don't fight it by looking for Department of Linguistics | substance in everything.

3 6

boost::threads is it all about managed threads?
by The Grumpiest Man You Know 11 Mar '05

11 Mar '05

I realize I might be trying to read beyond my experience level but I am having a blast and might even be getting somewhere learning a new programming style, a little. :) So, I've been looking at boost::threads and pthreads while considering a problem. I was never a believer in threads, I come from an SMP background and always found that for what I wanted to do, async IO beat the pants off threads. Not that I want to start a war, just that I want to explain why I'm happy with concurrent programming but a complete nonce case when discussing thread programming. I have an application in mind for comparison and it's not particularly complex but it's a monster in LOC, mainly due to the liberal use of FORTRAN in whatever language the compiler happens to take. But one of the things it does have, that I'd rather not re-implement, is a request service library. That library picks up an incoming request, goes and carries out the action and then returns the result. The requests are of unbounded duration and there are multiple clients so the service times are pretty sad. I think that sounds like a job for threads; no need to alter the service code, just replace the routine that returns the results and bob's your mum's brother and I can get 10 at a time all sleeping waiting for the requested IO. But to not scare the natives I'd prefer to have a single thread unless the load actually demands more. Now, my old C brain can see that the main thread can get it's thread ID from thread_self() and then just be one of the guys but I can't see how the boost::thread() can do anything but give me threads to manage. After stepping on myself with a vector<boost::thread> :) I think this is the tao of boost::thread: const boost::function0<void> run = &go; boost::thread_group grp; for(int i = 0; i < 100; i++) { grp.create_thread(go); } grp.join_all(); Is that right? What am I missing? How do I get a bunch of peer boost::threads? If you're still with me thanks very much for your time and help and let me know if I'm dragging the list off topic and I'll go find someone else to bug. -- Blue Skies

3 4

RE: [Boost-users] __stdcall with boost::function
by Olenhouse, Jason 11 Mar '05

11 Mar '05

Ben Hutchings wrote: > Olenhouse, Jason wrote: > > I'm trying to pass a member function pointer around to the Windows > > Service Control Manager through Windpws API functions, but > > I think I'm having troubles with the __stdcall convention. > <snip> > > No, the problem is passing a member function pointer. A > member function > pointer is not type-compatible with a function pointer with the same > parameter types, regardless of whether they have the same calling > convention. <snip> But I used boost::bind to get a function pointer to hide the implicit this. I thought that the purpose of boost::bind was for that reason. It seems that the way I did it was nearly successful other than function::target<>() returns a __cdecl function pointer instead of an __stdcall one, as indicated by the error that MSVC returns. Is my interpretation of what I'm seeing incorrect? BTW, I included the two defines, #define BOOST_BIND_ENABLE_STDCALL #define BOOST_MEM_FN_ENABLE_STDCALL to be able to bind __stdcall member function with the this object pointer (I forgot to mention this in the original post). -Jason

2 1

Re: Re: Serialization, multiple inheritance, bad cast at smart_cast.hpp:202
by Zoltan Szatmary 11 Mar '05

11 Mar '05

Dear Robert thank you for answering. > > class A > > class B : public A > > class C : public virtual B > > class D : public virtual B > > class E : public C, public D > > > > so, a classic diamond inheritance which the serialization lib is > > supposed to be able to tackle with. Now, if I have a piece of code > > like this > > > > boost::serialization::xml_oarchive oa(somestream); > > A *a = new E(); > > oa << BOOST_SERIALIZATION_NVP(a); > > > > it throws exception at the aforementioned line. Examining the template > > substitutions, template class T is substituted with const B* and > > template class U is substituted with const A. So, the program should > > do a downcast on a const A* to const B* which is ought to be possible. > > Your example does indicate whether A has any pure virtual functions or not. > The dynamic down cast will only function if A is polymorphic - that is has > at least one virtual function. Soooo, I would expect this work if A has at > least one virtual function and I would expect it to fail if has no virtual > function. Double check this and get back to us. Yes, A does have a virtual destructor. But originally A had more virtual member functions, I just trimmed them down when I wanted to locate the source of error. But yes, class A is still polymorphic. I try to attach the example code to this mail, I hope it will get through. Best regards Zoltan

1 0