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[atomic] can it bechecked that boost::atomic<T> *v = reinterpret_cast<boost::atomic<T>*>(var); is safe?
by Tim Odenthal 15 Sep '14

15 Sep '14

Dear experts, essentially, I use this type of reinterpret_cast for doubles, and it __seems__ to work fine. I compile-time check that the sizeof(boost::atomic<T>) == sizeof( T ), but is that enough to ensure that this will always work? Should/could I check alignment issues as well? Even if the "atomic_cast" function has a (small) run-time overhead, it would be very much worth it in my setting, where I actually want to safely add to a double at some location in memory. Obviously, I want to use boost::atomic to be system/compiler agnostic, since it's supposed to eventually run with clang, gcc, (linux, OS X) as well as MS compilers, and so far we didn't see the need to move to C++11... Thanks for any advice in advance Tim

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program_options Parsing Suboptions
by Robert 15 Sep '14

15 Sep '14

Hi, I am trying to use program_options to parse suboptions: Command –S “-a 1 –b test –c 1.2” (the suboptions in –S are to be passed into other programs) Using the example source code, I tried something like the code below, but get the following error The argument (‘ 1’) for option ‘—TestA’ is invalid. Apparently the space between –a and 1 is treated as part of the argument and thus will not convert to an integer. I tried at the top argument level (e.g. command –M 1) and it works as expected, so something about creating the vector of suboptions is confusing program_options. Any suggestions? Thanks very much. options_description desc("Allowed options"); desc.add_options()("subopt,S",value<string>(),"Sub Options"); variables_map vm; store(command_line_parser(ac, av).options(desc).run(), vm); vm.notify(); if (vm.count("subopt")) { string substring=vm["subopt"].as<string>(); boost::regex re("\\s+(?=-)"); boost::sregex_token_iterator i(substring.begin(), substring.end(), re, -1); boost::sregex_token_iterator j; vector<string> splitResults; copy(i,j,back_inserter(splitResults)); int ta; string tb; float tc; options_description subopt_desc("Suboptions"); subopt_desc.add_options() ("TestA,a", value<int>(&ta)->default_value(0), "integer") ("TestB,b",value<string>(&tb),"string") ("TestC,c",value<float>(&tc), "float") ; variables_map subopt_vm; store(command_line_parser(splitResults).options(subopt_desc).run(), subopt_vm); subopt_vm.notify(); cout<<"a="<<ta<<endl; cout<<"b="<<tb<<endl; cout<<"c="<<tc<<endl; } -- http://www.fastmail.fm - Choose from over 50 domains or use your own

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[graph] how to find all vertices reachable from one edge of a starting vertex
by Michael Marcin 14 Sep '14

14 Sep '14

How can I find all vertices reachable by following one specified out-edge? Is there already an algorithm that does this? If not I think I could do it by: - marking all vertices white - mark starting vertex gray - depth_first_visit the target of the specified edge Does this work?

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[container][slist] constant time splice_after
by Aaron Levy 14 Sep '14

14 Sep '14

What happens if I call slist::splice_after(this_iter, that_list, that_begin, that_end, nelems) with an nelems value that does not match std::distance(that_begin, that_end). In other words, is there any kind of validations performed on nelems and is it just used to update the size of the list? Aaron

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how to construct an iterator_archetype<single_pass_traversal_tag>
by Peter Johansson 13 Sep '14

13 Sep '14

Hi, I'm writing tests using the iterator_archetype [http://www.boost.org/doc/libs/1_55_0/libs/iterator/doc/iterator_archetypes.…] and get confused how to use a single_pass_iterator such as e.g. iterator_archetype<int, readable_iterator_t, single_pass_iterator> The default constructor does not work as expected (since single_pass_iterators are not necessarily default constructible). The copy constructor is not very useful and that is all can find. I noticed the detail::ctor_arg and was hoping there were a constructor thaing that struct as argument - but no. How am I supposed to construct this class if I e.g. wanna passed it to a function that I intend to test. Thank you, Peter

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[container][flat_map] Internal storage for flat_maps / flat_sets
by Aaron Levy 13 Sep '14

13 Sep '14

What is the type of the underlying contiguous storage used by the flat_map / flat_set containers? Does the following code make sense: flat_map<T> container; ... if (container.size() > 0) { const T& elem = *(container.begin()); const T& elem_1 = *(container.begin() + 1); assert(&elem_1 == &elem + 1); } Aaron

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Problem linking with boost::program_options with clang 3.5 (OSX)
by Jürgen Simon 12 Sep '14

12 Sep '14

Hello, I require OpenMP on OSX and had to build OpenMP/Clang to that end. The compiler reads as clang 3.5. For some reason, the compiler seems to have a problem linking executables with boost. I tried boost version 1.55 but got a compilation error. Boost 1.56 compiles with this warning: clang-3.5: warning: argument unused during compilation: '-finline-functions' but other than that compiles through and installs just fine. When trying to link an executable with program_options however, I get the following linker error: Undefined symbols for architecture x86_64: "__ZN5boost15program_options11to_internalERKSs", referenced from: __ZN5boost15program_options11to_internalISsEESt6vectorISsSaISsEERKS2_IT_SaIS5_EE in radolan2cf.cpp.o "__ZN5boost15program_options19options_descriptionC1ERKSsjj", referenced from: _main in radolan2cf.cpp.o "__ZN5boost15program_options20invalid_option_valueC1ERKSs", referenced from: __ZN5boost15program_options8validateIfcEEvRNS_3anyERKSt6vectorISbIT0_St11char_traitsIS5_ESaIS5_EESaIS9_EEPT_l in radolan2cf.cpp.o "__ZN5boost15program_options22error_with_option_nameC2ERKSsS3_S3_i", referenced from: __ZN5boost15program_options16validation_errorC2ENS1_6kind_tERKSsS4_i in radolan2cf.cpp.o "__ZN5boost15program_options6detail7cmdline21set_additional_parserENS_9function1ISt4pairISsSsERKSsEE", referenced from: __ZN5boost15program_options25basic_command_line_parserIcE12extra_parserENS_9function1ISt4pairISsSsERKSsEE in radolan2cf.cpp.o "__ZN5boost15program_options6detail7cmdlineC2ERKSt6vectorISsSaISsEE", referenced from: __ZN5boost15program_options25basic_command_line_parserIcEC2EiPKPKc in radolan2cf.cpp.o "__ZN5boost15program_options8validateERNS_3anyERKSt6vectorISsSaISsEEPSsi", referenced from: __ZNK5boost15program_options11typed_valueISscE6xparseERNS_3anyERKSt6vectorISsSaISsEE in radolan2cf.cpp.o "__ZN5boost15program_optionslsERSoRKNS0_19options_descriptionE", referenced from: _main in radolan2cf.cpp.o "__ZNK5boost15program_options22abstract_variables_mapixERKSs", referenced from: __ZNK5boost15program_options13variables_mapixERKSs in radolan2cf.cpp.o "__ZNK5boost15program_options22error_with_option_name23substitute_placeholdersERKSs", referenced from: __ZTVN5boost16exception_detail10clone_implINS0_19error_info_injectorINS_15program_options20invalid_option_valueEEEEE in radolan2cf.cpp.o __ZTVN5boost16exception_detail19error_info_injectorINS_15program_options20invalid_option_valueEEE in radolan2cf.cpp.o __ZTVN5boost15program_options20invalid_option_valueE in radolan2cf.cpp.o __ZTVN5boost15program_options16validation_errorE in radolan2cf.cpp.o __ZTVN5boost16exception_detail10clone_implINS0_19error_info_injectorINS_15program_options16validation_errorEEEEE in radolan2cf.cpp.o __ZTVN5boost16exception_detail19error_info_injectorINS_15program_options16validation_errorEEE in radolan2cf.cpp.o "__ZNK5boost15program_options29value_semantic_codecvt_helperIcE5parseERNS_3anyERKSt6vectorISsSaISsEEb", referenced from: __ZTVN5boost15program_options11typed_valueIfcEE in radolan2cf.cpp.o __ZTVN5boost15program_options11typed_valueISscEE in radolan2cf.cpp.o ld: symbol(s) not found for architecture x86_64 clang-3.5: error: linker command failed with exit code 1 (use -v to see invocation) I’m a little stumped as to how to fix this problem. Can someone help me out? Kind Regards, Jürgen

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[Range] Strange!
by Robert Jones 10 Sep '14

10 Sep '14

Can anyone explain why my last output line is garbage? #include <iostream> #include <boost/range/algorithm/copy.hpp> #include <boost/range/counting_range.hpp> #include <boost/range/adaptor/reversed.hpp> #include <boost/range/adaptor/transformed.hpp> #include <boost/phoenix/bind/bind_function.hpp> #include <boost/phoenix/core/argument.hpp> int doubled( int i ) { return i * 2; } template <typename Range> void print_it( const Range & range ) { boost::copy( range, std::ostream_iterator<int>( std::cout, " " ) ); std::cout << std::endl; } int main( ) { using boost::adaptors::reversed; using boost::adaptors::transformed; using boost::counting_range; using boost::phoenix::arg_names::_1; print_it( counting_range( 1, 5 ) ); print_it( counting_range( 1, 5 ) | reversed ); print_it( counting_range( 1, 5 ) | transformed( doubled ) ); print_it( counting_range( 1, 5 ) | reversed | transformed( doubled ) ); print_it( counting_range( 1, 5 ) | transformed( bind( doubled, _1 ) ) ); print_it( counting_range( 1, 5 ) | reversed | transformed( bind( doubled, _1 ) ) ); } Output is 1 2 3 4 4 3 2 1 2 4 6 8 8 6 4 2 2 4 6 8 -711713824 -711713824 -711713824 -711713824 Compiling with gcc-4.9.1, Boost 1.56 on Fedora 20 64-bit. Thx, Rob.

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[filesystem] directory_iterator and filter in 1.56.0
by Braden McDaniel 10 Sep '14

10 Sep '14

This sort of thing worked in Boost 1.55.0: #include <boost/filesystem.hpp> #include <boost/range.hpp> #include <boost/range/adaptor/filtered.hpp> struct pred { bool operator()(const boost::filesystem::directory_entry & dirent) const { return true; } }; int main() { const auto dirent_range = boost::make_iterator_range(boost::filesystem::directory_iterator("/"), boost::filesystem::directory_iterator()); const auto filtered_dirent_range = boost::adaptors::filter(dirent_range, pred()); } Not so in 1.56.0 [output from Apple's clang 3.4]: boost/concept_check.hpp:210:9: error: no viable conversion from 'boost::single_pass_traversal_tag' to 'boost::forward_traversal_tag' Y y = x; ^ ~ The full error output is much more verbose and I can provide it if desired; but the above is the gist of the situation, as I understand it: directory_iterators are SinglePass iterators; filter operates on ForwardTraversal iterators; and the SinglePass iterator cannot be converted to the ForwardTraversal one. Is this situation deliberate or an unintended side effect? Is there some similarly succinct means of filtering a file/directory listing? -- Braden McDaniel <braden(a)endoframe.com>

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Re: [Boost-users] [context] Compiling error with context and bind
by José 10 Sep '14

10 Sep '14

3 2