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

Conditional function definition with boost::enable_if
by Matthias Vallentin 20 Feb '09

20 Feb '09

Hi folks, I would like to define a function in a class only if a child defines it. In the below example, I would like the function f() to exist only in an object bar if it defines a function i(). So far, my approach with boost::enable_if failed because bar is not a complete type during examination. T is clearly incomplete at the time when b is defined. What would be the correct approach to solve this problem? #include <boost/type_traits/is_function.hpp> #include <boost/utility/enable_if.hpp> template <typename T> struct foo { typename boost::enable_if< typename boost::is_function<typename T::i>::type, void >::type f() { } }; struct bar : foo<bar> { void i() { } }; int main() { bar b; b.f(); // should only compile since bar defines i() return 0; } enable_if.cc: In instantiation of ‘foo<bar>’: enable_if.cc:16: instantiated from here enable_if.cc:10: error: invalid use of undefined type ‘struct bar’ enable_if.cc:16: error: forward declaration of ‘struct bar’ enable_if.cc: In function ‘int main()’: enable_if.cc:25: error: ‘struct bar’ has no member named ‘f’ Matthias -- Matthias Vallentin vallentin(a)icsi.berkeley.edu http://matthias.vallentin.cc

2 4

Thread synchronization
by John D 20 Feb '09

20 Feb '09

Hello I have a situation in which hundreds of threads potentially run side by side. They exchange minimal data and are fully in sync by way of a scoped mutex. Now I have a situation in which a single seperate thread runs alongside all the worker threads. This thread is responsible for keeping data sets used by the workers, current. Given the complexity and total alternation of the data onthis interval, my question is; Does boost threads allow my single thread to halt all other activity ,of all the other threads,from a single thread itself. This is what I need to accomplish and any guidance to this matter is a huge help. John

1 0

Formal Review: Boost.RangeEx
by Thorsten Ottosen 20 Feb '09

20 Feb '09

Dear Developers and Users, It's my pleasure to announce that the review of Neil Groves' RangeEx library starts today and lasts until March 3, 2009. What is it? +++++++++++ The library provide two very useful extensions to the range library 1. Range-based algorithms. E.g. boost::sort( rng ); which is a convenient wrapper of instead of std::sort( boost::begin(rng), boost::end(rng) ); But the new interface also allows for more expressive code because (on the fly) composition of algorithms suddenly is possible. 2. Range adaptors. E.g. std::vector<int> vec = ...; boost::copy( vec | boost::adaptors::reversed, std::ostream_iterator<int>( std::cout ) ); where the expression "vec | boost::adaptors::reversed" wraps the iterators of the range on the left in reverse iterators. The library provides a wide range (no pun intended) of Range adaptors, and they are a powerful way to create ranges on the fly and pass them to algorithms. Getting the library +++++++++++++++++++ The library may be downloaded from http://www.cs.aau.dk/~nesotto/boost/range_ex.zip or from the Boost vault under "Algorithms". The docs may be browsed online here http://www.cs.aau.dk/~nesotto/boost/libs/range/ Please note that the documentation is integrated with the current Range ilbrary. Therefore the relevant sections for the review is http://www.cs.aau.dk/~nesotto/boost/libs/range/doc/adaptors.html and http://www.cs.aau.dk/~nesotto/boost/libs/range/doc/algorithms.html The code may be browsed here: http://www.cs.aau.dk/~nesotto/boost/boost/range/ Notice the library is header only (exception: the adaptor tokenized() depends on Boost.Regex). Writing a review ++++++++++++++++ If you feel this is an interesting library, then please submit your review to the developer list (preferably), or to the review manager. Here are some questions you might want to answer in your review: - What is your evaluation of the design? - What is your evaluation of the implementation? - What is your evaluation of the documentation? - What is your evaluation of the potential usefulness of the library? - Did you try to use the library? With what compiler? Did you have any problems? - How much effort did you put into your evaluation? A glance? A quick - reading? In-depth study? - Are you knowledgeable about the problem domain? And finally, every review should answer this question: - Do you think the library should be accepted as a Boost library? Be sure to say this explicitly so that your other comments don't obscure your overall opinion. Special considerations ++++++++++++++++++++++ Various RangeEx like libraries have been implemented in the past. You might want to compare with those libraries when you form your oppinion: 1. John Torjo's range lib http://rangelib.synesis.com.au/libs/boost-rangelib-20040913.zip http://torjo.com/rangelib/index.html 2. Adobe's ASL libraries include range-based algorithms: http://stlab.adobe.com/group__algorithm.html I'm looking forward to your review. best regards Thorsten, Review Manager

1 0

[Q] storing function pointers to member function
by V S P 20 Feb '09

20 Feb '09

I am trying to come up with a system that would let me have a function (getter) for every member of the class Using macros I can generate a 'get_<membername> function such that struct my { float mem1; } would be struct my { float mem1; static const float& get_mem1( const my& ) { return my.mem1; } }; Now, I would like to store pointer to the get_mem1 function in a staticaly declared std::map Using boost/function.hpp I can declare a type for float typedef boost::function<const float& (const my& ,const char* )> tFget__float ; and then I can store it in, for example std::set<tFget__float> The problem is that if I have another function that returns a different data type (something other than float, for example std::string) I get a compilation error when trying to insert that function pointer into the set. There is a check implemented, I think, via the template system that prevents compiler from making copies of one ponter type to another -- even though they only differ by return type. When I just do the assignment tFget__float x= <function returning float> or to function returning std::string -- I do not get the error. So I would like to ask -- if there is a good way to store function pointers in a static array (I later on plan to iterate ove the set of function pointers and get the value of each data member into a stream ) thanks in advance, Vlad -- V S P toreason(a)fastmail.fm -- http://www.fastmail.fm - The professional email service

1 0

[serialization][build][spirit] Problems with spirit when building 1.38 serialization on windows with Intel C++ 11.0
by Jesse Perla 20 Feb '09

20 Feb '09

I am on windows using the latest version of the intel compiler (set in my user-config.jam). I was able to do a debug build of everything using: bjam link=static debug stage But when I tried to do a release build, it is popping up a spirit error for serialization. (fails with or without mpi) Any ideas on a workaround? See below: C:\apps\boost\boost_1_38_0>bjam --with-mpi link=static release stage ...patience... ...found 1080 targets... ...updating 4 targets... compile-c-c++ bin.v2\libs\serialization\build\intel-win\release\link-static\thre ading-multi\xml_grammar.obj icl: command line remark #10010: option '/Op' is deprecated and will be removed in a future release. See '/help deprecated' xml_grammar.cpp Warning: This header is deprecated. Please use: boost/spirit/include/classic_rul e.hpp Warning: This header is deprecated. Please use: boost/spirit/include/classic_ope rators.hpp Warning: This header is deprecated. Please use: boost/spirit/include/classic_act ions.hpp Warning: This header is deprecated. Please use: boost/spirit/include/classic_num erics.hpp C:\apps\boost\boost_1_38_0\boost\spirit\home\classic\utility\impl\chset\range_ru n.ipp(142) (col. 21): internal error: 0_1504 compilation aborted for libs\serialization\src\xml_grammar.cpp (code 4) call "C:\apps\Intel\Compiler\11.0\066\cpp\bin\ia32\iclvars_ia32.bat" > nul icl @"bin.v2\libs\serialization\build\intel-win\release\link-static\threading-mu lti\xml_grammar.obj.rsp" ...failed compile-c-c++ bin.v2\libs\serialization\build\intel-win\release\link-s tatic\threading-multi\xml_grammar.obj... ...skipped <pbin.v2\libs\serialization\build\intel-win\release\link-static\threa ding-multi>libboost_serialization-iw-mt-1_38.lib for lack of <pbin.v2\libs\seria lization\build\intel-win\release\link-static\threading-multi>xml_grammar.obj... ...skipped <pstage\lib>libboost_serialization-iw-mt-1_38.lib for lack of <pbin.v 2\libs\serialization\build\intel-win\release\link-static\threading-multi>libboos t_serialization-iw-mt-1_38.lib... ...skipped <pstage\lib>libboost_serialization-iw-mt.lib for lack of <pstage\lib> libboost_serialization-iw-mt-1_38.lib... ...failed updating 1 target... ...skipped 3 targets...

1 0

[Test] Compilation inconsistency
by Greg Ravikovich 19 Feb '09

19 Feb '09

Hello, I posted a question regarding the following issue a few months back: Empty cpp file containing only: #include <boost/test/test_case_template.hpp> Fails to compile, however an empty cpp file containing #include <boost/test/unit_test.hpp> #include <boost/test/test_case_template.hpp> Compiles fine. The issue is still there in boost 1.38. Can someone address it please? Thanks. Greg

3 2

[Proto] Failure on VC9
by Joel Falcou 19 Feb '09

19 Feb '09

I've been tryign to port some of my proto code to VC9 but it seems I failed. The code compiles fine but when I try to use any of my newly defined operator on my terminal, VC9 complains it cna't find them. What can be the reason of this symptoms as the same code works on both gcc and icc ?

2 3

if_then_else_return (boost::lambda) question
by Jonathan Leonard 19 Feb '09

19 Feb '09

Greetings! I'm fairly new to boost and have a little problem with if_then_else_return. Can anyone tell me the problem with the following short program? [It seems that my 'thenBranch' and 'elseBranch' functions are never called and if_then_else_return' always returns true (as if the 'then' branch were called)]. Many thanks in advance for any help you may offer! P.S. (A more general C++ q: A little improvement I'd like to make is to drop the ITERATORTYPE type argument from IfNotEndThenElseReturn and use CONTAINERTYPE::iterator instead, but the compiler won't allow that. Anyone know why?). Thanks again! ============================================ #include <boost/lambda/lambda.hpp> #include <boost/lambda/if.hpp> #include <boost/lambda/bind.hpp> #include <boost/function.hpp> #include <functional> #include <list> using namespace boost::lambda; template<typename RET> RET InvokeReturn(boost::function<void ()> f, const RET& retVal) { printf("in InvokeReturn!\n"); f(); return retVal; } bool InvokeReturnTrue(boost::function<void ()> f) { return InvokeReturn(f, true); } bool InvokeReturnFalse(boost::function<void ()> f) { return InvokeReturn(f, false); } boost::function<bool ()> MakeReturnTrue(boost::function<void ()> f) { printf("in MakeReturnTrue!\n"); return boost::lambda::bind(&InvokeReturnTrue, f); } boost::function<bool ()> MakeReturnFalse(boost::function<void ()> f) { printf("in MakeReturnFalse!\n"); return boost::lambda::bind(&InvokeReturnFalse, f); } template<typename CONTAINERTYPE, typename ITERATORTYPE> bool IfNotEndThenElseReturn(const ITERATORTYPE& it, CONTAINERTYPE& container, boost::function<void ()> thenBranch, boost::function<void ()> elseBranch) { printf("in IfNotEndThenElseReturn!\n"); std::not_equal_to<ITERATORTYPE> ne; return boost::lambda::if_then_else_return( boost::lambda::bind(&std::not_equal_to<ITERATORTYPE>::operator(), ne, it, container.end()), MakeReturnTrue(thenBranch), MakeReturnFalse(elseBranch))(); } void thenBranch() { printf("in then branch!\n"); } void elseBranch() { printf("in else branch!\n"); } int _tmain(int argc, _TCHAR* argv[]) { printf("beginning execution!\n"); std::list<int> l; l.push_back(8); l.push_back(7); l.push_back(6); l.push_back(5); std::list<int>::iterator it = l.end(); std::list<int>::iterator it2 = l.begin(); bool b = IfNotEndThenElseReturn(it, l, bind(&thenBranch), bind(&elseBranch)); printf("b is %s\n", b ? "true" : "false"); bool b = IfNotEndThenElseReturn(it2, l, bind(&thenBranch), bind(&elseBranch)); printf("b is %s\n", b ? "true" : "false"); printf("finished!\n"); return 0; }

2 2

Order of composite units in the output
by Esben Mose Hansen 19 Feb '09

19 Feb '09

Hi, I think I am beginning to get the boost:units library, but I still have one problem. Consider: #include <iostream> #include <boost/units/io.hpp> #include <boost/units/systems/si/length.hpp> #include <boost/units/make_system.hpp> #include <boost/units/quantity.hpp> #include <boost/units/base_dimension.hpp> #include <boost/units/base_unit.hpp> #include <boost/units/derived_dimension.hpp> // Introduce slot (measured in e.g. ffe or tfe) as a basic dimension, unit and in a system struct slot_base_dimension : boost::units::base_dimension<slot_base_dimension, 1> { }; typedef slot_base_dimension::dimension_type slot_dimension; struct ffe_base_unit : public boost::units::base_unit<ffe_base_unit, slot_dimension, 1> { static std::string name() { return("40ft equivalent"); } static std::string symbol() { return("ffe"); } }; typedef ffe_base_unit::unit_type slot_t; BOOST_UNITS_STATIC_CONSTANT(ffe, slot_t); /// derived dimension (slot) flow typedef boost::units::derived_dimension<slot_base_dimension,1,boost::units::time_base_dimension,-1>::type flow_dimension; /// placeholder class defining si unit system typedef boost::units::make_system<boost::units::si::meter_base_unit, boost::units::si::second_base_unit, ffe_base_unit>::type unit_system; typedef boost::units::unit<flow_dimension,unit_system> flow_t; BOOST_UNITS_STATIC_CONSTANT(ffe_per_second, flow_t); int main() { boost::units::quantity<flow_t> flow(4*ffe_per_second); std::cout << "flow= " << flow << std::endl; } This program outputs flow= 4 s^-1 ffe which is correct, but a bit unusual... 4 ffe/s or even 4 ffe s^-1 would have been better. Is this possible? Thanks! -- kind regards, Esben

3 2

[serialization|TR1] serialization impementation for std::tr1::tuple?
by Markus Werle 19 Feb '09

19 Feb '09

Hi! Sorry, if this has been discussed before. I am too stupid (and tired) to find the equivalent for tuple_io.hpp for the boost tr1::tuple implementation. So is there already some serialization and/or I/O implementation for a tr1::tuple available somewhere? The proposal at http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2002/n1403.pdf mentions operator<<, but VC9 SP1 refuses to find one if I #include <boost/tr1/tuple.hpp> or <tuple>. Is this another VC9 bug? I could not find the compiler flag which hinders M$'s implementation of TR1 ... Any pointer appreciated. best regards, Markus

2 1