July 2009 - Boost-users - lists.preview.boost.org

[Math Toolkit] Gamma Distribution
by Christian Henning 21 Jul '09

21 Jul '09

Hi there, the documention of the gamma distribution talks about two different forms. How can can generate the second one with shape=1 and scale=1? I know how to get the first form: boost::math::gamma_distribution<> dist( 1, 1 ); I don't see how to get the second one? Thanks, Christian

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Spirit 1.39 compilation times
by Avi Bahra 21 Jul '09

21 Jul '09

>First, you should use Boost Trunk, it compiles quite noticeably faster. >Second, look in the Spirit examples directly with Boost Trunk, in the >QI subdirectory, the mini_c directory has an example of just that. I cant use use boost trunk, in order to get faster compiles, since I have to use boost1.38/1.39. Also it looks like the grammar construction in the examples is different. I looked for a similar example in boost 1.39 since we use closures but none exists. Surely anyone who is using spirit and building on multiple platforms must be be affected with this bug ? Best regards. Avi ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////// Message: 4 Date: Mon, 20 Jul 2009 10:37:57 +0100 From: Avi Bahra <avibahra(a)googlemail.com> Subject: [Boost-users] Spirit 1.39 compilation times To: boost-users(a)lists.boost.org Message-ID: <af1b101f0907200237ofdf91bbk98be95d0ab817208(a)mail.gmail.com> Content-Type: text/plain; charset="iso-8859-1" I am using boost spirit 1.39. On gcc the compilation times are acceptable. However on AIX with v10.1 compiler, it fails to even compile. After 24hrs waiting, I gave up. Ok I realise that the grammer needs to split. Is there any _small_ examples out there, that demonstrates this technique for a beginner ? In my case I have one grammer and ~70 rules. Take the following rule: rule<ScannerT, string_closure::context_t> identifier ; identifier = lexeme_d [ (alnum_p || ch_p('_')) >> *(alnum_p || ch_p('_')) ] [ identifier.name = construct_<std::string>(arg1, arg2) ] ; What is the technique for converting it into a grammer, that is separately compiled ? Also how would I reference it again, without including the header file, from another rule dotPath = ( str_p(".") >> +( str_p("/") >> identifier ) ) [ dotPath.name = construct_<std::string>(arg1, arg2) ] ; Any help would greatly appreciated. Best regards, Ta, Avi

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[data_time] Are posix_time functions reentrant ?
by Ruediger Berlich 21 Jul '09

21 Jul '09

Hi there, here is a question I didn't find answers on in the documentation: Are the posix_time functions reentrant ? In particular: In my library a number of threads instantiate objects that internally measure the elapsed time like this: // Measure the start time ptime startTime = boost::posix_time::microsec_clock::local_time(); // [...] // Has a time-out been set and if so, have we exceeded it ? if(firstTimeOut_.total_microseconds() && ((microsec_clock::local_time()-startTime) > firstTimeOut_)) { // do something } Best Regards, Ruediger

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A question on member functions in a class using lambda expression? Can anyone with kindness help me?
by fmingu 21 Jul '09

21 Jul '09

I am using Dev-C++ 4.9.8.0,with lambda expression: ...................... class A{ ............. int result; double function2(const int& n) ......................... double function3(const int& Q,const int& N) ...................... double function1(const int& q, int& n){ double result=0.0; int loopvalue=0, totaltime=n; n%=q; ++thenumbern; ( for_loop(var(loopvalue)=0,var(loopvalue)<=var(totaltime),++var(loopvalue), var(result)+=( bind(&A::function2,_2)*bind(&A::function3,_1,_2))))(q,n); return result; } But the complier told me that: ............................... \boost\lambda\detail\select_functions.hpp instantiated from `Arg::sig<boost::tuples::tuple<A&,................. instantiated from `RET boost::lambda::lambda_functor_base<boost::lambda::forloop_action, Args>::call(A&, B&, C.................... \boost\lambda\detail\lambda_functors.hpp instantiated from `T::sig<boost::tuples::tuple<A&, B&, boost::tuples::null_type, boost::tuples::null_type, ............... instantiated from here By the way, is the result in var(result) the double result in function1 or the int result in class A? Can any one with kindness help me?

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[asio] async_resolve problems
by Roman Shmelev 21 Jul '09

21 Jul '09

Hi! I've written _test_ dummy service, working in single thread (prototype for more useful app). It accepts strings like "google.com" (and "gosdkfjslfjle.com"), resolves them and returns ip of the host. I noticed, that bad hostnames make it think too much, preventing other requests from being processed. So, I decided to use async_resolve approach, hoping that now I will be able to handle many requests concurrently. But it seems that async_resolve is not as async as desired - it feels like separate thread resolves in sync way all hosts. The question is - how to make async_resolve be really async? Am I missing something?

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Suggestions/advice using boost::test
by Ahmed Badran 21 Jul '09

21 Jul '09

Hi, I want to use boost test in a particular way, I'm not sure if it's even possible, suggestions/advice are greatly appreciated. I have a shared library consisting of many classes. I would like to write my BOOST_AUTO_TEST_CASE at the end of the implementation of each class so as to encourage always writing tests. So this is what I've done, included <boost/test/unit_test.hpp> in the implementation file of each class, and wrote the test cases for each class at the end of the .cpp file for that class. In one of the .cpp files, I've stuck the following at the top to produce a canned 'main': #ifdef TEST #define BOOST_TEST_MAIN #include <boost/test/included/unit_test.hpp> #endif and compiled this particular file twice, so now I have a library without a main, and an executable with a main. The self-contained executable runs the tests perfectly as intended. The problem is that now the library is dependent on boost::test, any program that links against this library now needs to also link against the boost::test library (otherwise I get linker errors) which is _highly_ undesirable. It is perfectly fine however, if the tests get included/instantiated in the library but never get called, that's a perfectly valid solution. I also don't want to wrap the inclusion/code for the tests in ifdefs, since this will mean that the code (which is a lot) will have to be compiled twice and this process gets messy and tedious. Is there a way to accomplish this? Regards, Ahmed

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[python][lambda] thin wrapper functions using boost.lambda
by Václav Šmilauer 21 Jul '09

21 Jul '09

Hi, I would like to use lambda functions to define thin wrapper functions in boost::python, like struct A{ void meth1(); }; [...] python::class_<A>("A").def("meth1",lambda::bind(&A::meth1,lambda::_1)); and I am getting "error: no matching function for call to 'get_signature [...]' " from the compiler. Reading boost::lambda documentation (http://www.boost.org/doc/libs/1_39_0/doc/html/lambda/using_library.html#lam…) """The basic rule is that a lambda function can be called with arguments of any types, as long as the lambda expression with substitutions performed is a valid C++ expression.""" Is there a way to enforce parameter types, so that boost::python can get the signature? Or, more generally, is it somehow possible to use such in-place functions to create the thin wrappers? Many thanks, Vaclav

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variant<T&> with throwing initialization code.
by Zachary Turner 20 Jul '09

20 Jul '09

I have a couple of variants whose inner type are all references. For example, variant<a1&, a2&, ...> var1; variant<b1&, b2&, ...> var2; Because this variant will not be assignable due to the references, they need to be initialized in a constructor initializer list. However, it's possible for the function that creates these references in the first place to throw, and moreover the inner types might contain unmanaged resources that need to be properly cleaned up on a throw. Also the construction of var_k, might depend upon the successful construction of var_j where j<k (like for example I might need to use some member variable in one of the previously constructed objects to pass to one of the later objects to construct it). Is there a decent way to handle this? The problem is that if, say, something throws while trying to create var2, but var1 has already been created, then var1's unmanaged resources need to be properly freed. I tried to package all the variants together in a class such as typedef variant<a1&, a2&, ...> v1_type; typedef variant<b1&, b2&, ...> v2_type; struct package { package(v1_type& v1, v2_type& v2) : var1_(v1), var2_(v2) { } v1_type var1_; v2_type var2_; }; and then only have one instance of package in my class. Then, in the initializer list call package_(create_package()), and define create_package() as: package create_package() { optional<v1_type> v1; optional<v2_type> v2; try { v1 = create_v1(); v2 = create_v2(); return package(v1.get(), v2.get()); } catch(...) { } } but for some reason this fails to compile, saying that it's trying to call variant::operator= in the package constructor. Which doesn't make sense since I don't think it should be.

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BGL: copy_graph does not work with bundled properties
by caligulaemperorofrome＠yahoo.com 20 Jul '09

20 Jul '09

Hi, copy_graph is not working with bundled property. See this minimal example program (40 lines) at http://tinyurl.com/lxh577. Just download make and execute - very easy. Thanks - Caligula

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remove boost variable names from gcc compiled file
by ndgs＠lpemail.com 20 Jul '09

20 Jul '09

After I compile my file with g++ using the -s flag all that is striped out are my own variable names. I used xxd to look a the compiled output and "boost" is still all over the binary. How can I remove them? I used g++ with /usr/lib/librt.a and /usr/local/lib/libboost_thread-gcc43-mt.a I want to release this as a binary with no source code and I would prefer it if there wasn't boost this and boost that in the binary. Thanks, Piano

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