March 2011 - Boost-users - lists.preview.boost.org

Preventing iostreams from accessing freed memory
by Adam Nielsen 14 Mar '11

14 Mar '11

Hi all, I'm unable to prevent Boost iostreams from accessing memory once it has been freed, and I'm hoping someone here familiar with iostreams has some advice. As far as I can tell, when I push a standard iostream onto a filter, the filter holds on to a reference of it. If this happens inside a function, then when the function returns the iostream is freed, followed by the filter. In its destructor the filter tries to perform a flush/close and promptly segfaults, as it is trying to access the iostream which has just been freed. There is a set_auto_close() function I can call on the filter which sounds like it would do the trick, but it doesn't and according to the docs it's because it "does not prevent the Filters and Devices in the chain from being closed [flushed] automatically if the chain is complete at destruction." So is there any way I can prevent a filtering_stream from performing I/O in its destructor? Thanks, Adam.

1 1

[property tree][json]how to create empty array?
by Kulti 12 Mar '11

12 Mar '11

Hi, all! It's possible to get following output from boost::property_tree::json_parser::write_json ? { "id": "id", "method": "test_method", "params": [] } I know how to create array with some items, but when I try to create empty array, I've get "params": ""

3 3

temporary filenames
by Kraus Philipp 12 Mar '11

12 Mar '11

Hello, is there any implementation for creating temporary files names? I'm using tmpnam, but it can be dangerous. On posix systems I can use mkstemp. Is there any save implementation within the boost (perhaps in the iostreams)? Thanks Phil

2 2

boost-users@lists.boost.org
by Stephen Hewitt 12 Mar '11

12 Mar '11

I have recently upgraded to Boost 1.46 and am having trouble compiling the following simple program (Using Visual Studio 2005): // Error.cpp : Defines the entry point for the console application. // #include "stdafx.h" #include <tchar.h> #include <iostream> #include <boost/property_tree/ptree.hpp> #include <boost/property_tree/json_parser.hpp> void Go() { boost::property_tree::ptree t; boost::property_tree::read_json(std::cin, t); } int _tmain(int argc, _TCHAR* argv[]) { Go(); return 0; } Here are the errors I get: 1>------ Build started: Project: Error, Configuration: Debug Win32 ------ 1>Compiling... 1>stdafx.cpp 1>Compiling... 1>Error.cpp 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(184) : error C2872: 'assertion' : ambiguous symbol 1> could be 'boost::assertion' 1> or 'c:\libraries\boost_1_46_0\boost\spirit\home\classic\error_handling\exceptions.hpp(187) : boost::spirit::classic::assertion' 1> c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(178) : while compiling class template member function 'boost::property_tree::json_parser::json_grammar<Ptree>::definition<Scanner>::definition(const boost::property_tree::json_parser::json_grammar<Ptree> &)' 1> with 1> [ 1> Ptree=boost::property_tree::ptree, 1> Scanner=scanner_t 1> ] 1> c:\libraries\boost_1_46_0\boost\spirit\home\classic\core\non_terminal\impl\grammar.ipp(279) : see reference to class template instantiation 'boost::property_tree::json_parser::json_grammar<Ptree>::definition<Scanner>' being compiled 1> with 1> [ 1> Ptree=boost::property_tree::ptree, 1> Scanner=scanner_t 1> ] 1> c:\libraries\boost_1_46_0\boost\spirit\home\classic\core\non_terminal\impl\grammar.ipp(298) : see reference to function template instantiation 'void boost::spirit::classic::impl::call_helper<0>::do_<result_t,definition_t,ScannerT>(RT &,DefinitionT &,const ScannerT &)' being compiled 1> with 1> [ 1> ScannerT=scanner_t, 1> RT=result_t, 1> DefinitionT=definition_t 1> ] 1> c:\libraries\boost_1_46_0\boost\spirit\home\classic\core\non_terminal\grammar.hpp(55) : see reference to function template instantiation 'boost::spirit::classic::match<boost::spirit::classic::nil_t> boost::spirit::classic::impl::grammar_parser_parse<0,boost::property_tree::json_parser::json_grammar<Ptree>,boost::spirit::classic::parser_context<>,ScannerT>(const boost::spirit::classic::grammar<DerivedT> *,const ScannerT &)' being compiled 1> with 1> [ 1> Ptree=boost::property_tree::ptree, 1> ScannerT=scanner_t, 1> DerivedT=boost::property_tree::json_parser::json_grammar<boost::property_tree::ptree> 1> ] 1> c:\libraries\boost_1_46_0\boost\spirit\home\classic\core\non_terminal\grammar.hpp(65) : see reference to function template instantiation 'boost::spirit::classic::match<boost::spirit::classic::nil_t> boost::spirit::classic::grammar<DerivedT>::parse_main<ScannerT>(const ScannerT &) const' being compiled 1> with 1> [ 1> DerivedT=boost::property_tree::json_parser::json_grammar<boost::property_tree::ptree>, 1> ScannerT=scanner_t 1> ] 1> c:\libraries\boost_1_46_0\boost\spirit\home\classic\core\scanner\impl\skipper.ipp(109) : see reference to function template instantiation 'boost::spirit::classic::match<boost::spirit::classic::nil_t> boost::spirit::classic::grammar<DerivedT>::parse<scanner_t>(const ScannerT &) const' being compiled 1> with 1> [ 1> DerivedT=boost::property_tree::json_parser::json_grammar<boost::property_tree::ptree>, 1> ScannerT=scanner_t 1> ] 1> c:\libraries\boost_1_46_0\boost\spirit\home\classic\core\scanner\impl\skipper.ipp(155) : see reference to function template instantiation 'boost::spirit::classic::parse_info<IteratorT> boost::spirit::classic::impl::phrase_parser<SkipT>::parse<IteratorT,DerivedT>(const IteratorT &,const IteratorT &,const ParserT &,const SkipT &)' being compiled 1> with 1> [ 1> IteratorT=It, 1> SkipT=boost::spirit::classic::alternative<boost::spirit::classic::alternative<boost::spirit::classic::space_parser,boost::spirit::classic::confix_parser<boost::spirit::classic::impl::string_as_parser::type,boost::spirit::classic::kleene_star<boost::spirit::classic::anychar_parser>,boost::spirit::classic::alternative<boost::spirit::classic::eol_parser,boost::spirit::classic::end_parser>,boost::spirit::classic::unary_parser_category,boost::spirit::classic::non_nested,boost::spirit::classic::is_lexeme>>,boost::spirit::classic::confix_parser<boost::spirit::classic::impl::string_as_parser::type,boost::spirit::classic::kleene_star<boost::spirit::classic::anychar_parser>,boost::spirit::classic::impl::string_as_parser::type,boost::spirit::classic::unary_parser_category,boost::spirit::classic::non_nested,boost::spirit::classic::is_lexeme>>, 1> DerivedT=boost::property_tree::json_parser::json_grammar<boost::property_tree::ptree>, 1> ParserT=boost::property_tree::json_parser::json_grammar<boost::property_tree::ptree> 1> ] 1> c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(312) : see reference to function template instantiation 'boost::spirit::classic::parse_info<IteratorT> boost::spirit::classic::parse<std::_Vector_iterator<_Ty,_Alloc>,DerivedT,boost::spirit::classic::alternative<A,B>>(const IteratorT &,const IteratorT &,const boost::spirit::classic::parser<DerivedT> &,const boost::spirit::classic::parser<boost::spirit::classic::alternative<A,B>> &)' being compiled 1> with 1> [ 1> IteratorT=It, 1> _Ty=Ch, 1> _Alloc=std::allocator<char>, 1> DerivedT=boost::property_tree::json_parser::json_grammar<boost::property_tree::ptree>, 1> A=boost::spirit::classic::alternative<boost::spirit::classic::space_parser,boost::spirit::classic::confix_parser<boost::spirit::classic::impl::string_as_parser::type,boost::spirit::classic::kleene_star<boost::spirit::classic::anychar_parser>,boost::spirit::classic::alternative<boost::spirit::classic::eol_parser,boost::spirit::classic::end_parser>,boost::spirit::classic::unary_parser_category,boost::spirit::classic::non_nested,boost::spirit::classic::is_lexeme>>, 1> B=boost::spirit::classic::confix_parser<boost::spirit::classic::impl::string_as_parser::type,boost::spirit::classic::kleene_star<boost::spirit::classic::anychar_parser>,boost::spirit::classic::impl::string_as_parser::type,boost::spirit::classic::unary_parser_category,boost::spirit::classic::non_nested,boost::spirit::classic::is_lexeme> 1> ] 1> c:\libraries\boost_1_46_0\boost\property_tree\json_parser.hpp(45) : see reference to function template instantiation 'void boost::property_tree::json_parser::read_json_internal<Ptree>(std::basic_istream<_Elem,_Traits> &,Ptree &,const std::string &)' being compiled 1> with 1> [ 1> Ptree=boost::property_tree::ptree, 1> _Elem=char, 1> _Traits=std::char_traits<char> 1> ] 1> c:\users\steve\documents\visual studio 2005\projects\error\error.cpp(13) : see reference to function template instantiation 'void boost::property_tree::json_parser::read_json<boost::property_tree::ptree>(std::basic_istream<_Elem,_Traits> &,Ptree &)' being compiled 1> with 1> [ 1> _Elem=char, 1> _Traits=std::char_traits<char>, 1> Ptree=boost::property_tree::ptree 1> ] 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(184) : error C2872: 'assertion' : ambiguous symbol 1> could be 'boost::assertion' 1> or 'c:\libraries\boost_1_46_0\boost\spirit\home\classic\error_handling\exceptions.hpp(187) : boost::spirit::classic::assertion' 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(184) : error C2872: 'assertion' : ambiguous symbol 1> could be 'boost::assertion' 1> or 'c:\libraries\boost_1_46_0\boost\spirit\home\classic\error_handling\exceptions.hpp(187) : boost::spirit::classic::assertion' 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(184) : error C2872: 'assertion' : ambiguous symbol 1> could be 'boost::assertion' 1> or 'c:\libraries\boost_1_46_0\boost\spirit\home\classic\error_handling\exceptions.hpp(187) : boost::spirit::classic::assertion' 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(184) : error C2882: 'assertion' : illegal use of namespace identifier in expression 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(184) : error C3861: 'expect_object': identifier not found 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(185) : error C2872: 'assertion' : ambiguous symbol 1> could be 'boost::assertion' 1> or 'c:\libraries\boost_1_46_0\boost\spirit\home\classic\error_handling\exceptions.hpp(187) : boost::spirit::classic::assertion' 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(185) : error C2872: 'assertion' : ambiguous symbol 1> could be 'boost::assertion' 1> or 'c:\libraries\boost_1_46_0\boost\spirit\home\classic\error_handling\exceptions.hpp(187) : boost::spirit::classic::assertion' 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(185) : error C2872: 'assertion' : ambiguous symbol 1> could be 'boost::assertion' 1> or 'c:\libraries\boost_1_46_0\boost\spirit\home\classic\error_handling\exceptions.hpp(187) : boost::spirit::classic::assertion' 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(185) : error C2872: 'assertion' : ambiguous symbol 1> could be 'boost::assertion' 1> or 'c:\libraries\boost_1_46_0\boost\spirit\home\classic\error_handling\exceptions.hpp(187) : boost::spirit::classic::assertion' 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(185) : error C2882: 'assertion' : illegal use of namespace identifier in expression 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(185) : error C3861: 'expect_eoi': identifier not found 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(186) : error C2872: 'assertion' : ambiguous symbol 1> could be 'boost::assertion' 1> or 'c:\libraries\boost_1_46_0\boost\spirit\home\classic\error_handling\exceptions.hpp(187) : boost::spirit::classic::assertion' 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(186) : error C2872: 'assertion' : ambiguous symbol 1> could be 'boost::assertion' 1> or 'c:\libraries\boost_1_46_0\boost\spirit\home\classic\error_handling\exceptions.hpp(187) : boost::spirit::classic::assertion' 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(186) : error C2872: 'assertion' : ambiguous symbol 1> could be 'boost::assertion' 1> or 'c:\libraries\boost_1_46_0\boost\spirit\home\classic\error_handling\exceptions.hpp(187) : boost::spirit::classic::assertion' 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(186) : error C2872: 'assertion' : ambiguous symbol 1> could be 'boost::assertion' 1> or 'c:\libraries\boost_1_46_0\boost\spirit\home\classic\error_handling\exceptions.hpp(187) : boost::spirit::classic::assertion' 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(186) : error C2882: 'assertion' : illegal use of namespace identifier in expression 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(186) : error C3861: 'expect_objclose': identifier not found 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(187) : error C2872: 'assertion' : ambiguous symbol 1> could be 'boost::assertion' 1> or 'c:\libraries\boost_1_46_0\boost\spirit\home\classic\error_handling\exceptions.hpp(187) : boost::spirit::classic::assertion' 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(187) : error C2872: 'assertion' : ambiguous symbol 1> could be 'boost::assertion' 1> or 'c:\libraries\boost_1_46_0\boost\spirit\home\classic\error_handling\exceptions.hpp(187) : boost::spirit::classic::assertion' 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(187) : error C2872: 'assertion' : ambiguous symbol 1> could be 'boost::assertion' 1> or 'c:\libraries\boost_1_46_0\boost\spirit\home\classic\error_handling\exceptions.hpp(187) : boost::spirit::classic::assertion' 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(187) : error C2872: 'assertion' : ambiguous symbol 1> could be 'boost::assertion' 1> or 'c:\libraries\boost_1_46_0\boost\spirit\home\classic\error_handling\exceptions.hpp(187) : boost::spirit::classic::assertion' 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(187) : error C2882: 'assertion' : illegal use of namespace identifier in expression 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(187) : error C3861: 'expect_arrclose': identifier not found 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(188) : error C2872: 'assertion' : ambiguous symbol 1> could be 'boost::assertion' 1> or 'c:\libraries\boost_1_46_0\boost\spirit\home\classic\error_handling\exceptions.hpp(187) : boost::spirit::classic::assertion' 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(188) : error C2872: 'assertion' : ambiguous symbol 1> could be 'boost::assertion' 1> or 'c:\libraries\boost_1_46_0\boost\spirit\home\classic\error_handling\exceptions.hpp(187) : boost::spirit::classic::assertion' 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(188) : error C2872: 'assertion' : ambiguous symbol 1> could be 'boost::assertion' 1> or 'c:\libraries\boost_1_46_0\boost\spirit\home\classic\error_handling\exceptions.hpp(187) : boost::spirit::classic::assertion' 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(188) : error C2872: 'assertion' : ambiguous symbol 1> could be 'boost::assertion' 1> or 'c:\libraries\boost_1_46_0\boost\spirit\home\classic\error_handling\exceptions.hpp(187) : boost::spirit::classic::assertion' 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(188) : error C2882: 'assertion' : illegal use of namespace identifier in expression 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(188) : error C3861: 'expect_name': identifier not found 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(189) : error C2872: 'assertion' : ambiguous symbol 1> could be 'boost::assertion' 1> or 'c:\libraries\boost_1_46_0\boost\spirit\home\classic\error_handling\exceptions.hpp(187) : boost::spirit::classic::assertion' 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(189) : error C2872: 'assertion' : ambiguous symbol 1> could be 'boost::assertion' 1> or 'c:\libraries\boost_1_46_0\boost\spirit\home\classic\error_handling\exceptions.hpp(187) : boost::spirit::classic::assertion' 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(189) : error C2872: 'assertion' : ambiguous symbol 1> could be 'boost::assertion' 1> or 'c:\libraries\boost_1_46_0\boost\spirit\home\classic\error_handling\exceptions.hpp(187) : boost::spirit::classic::assertion' 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(189) : error C2872: 'assertion' : ambiguous symbol 1> could be 'boost::assertion' 1> or 'c:\libraries\boost_1_46_0\boost\spirit\home\classic\error_handling\exceptions.hpp(187) : boost::spirit::classic::assertion' 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(189) : error C2882: 'assertion' : illegal use of namespace identifier in expression 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(189) : error C3861: 'expect_colon': identifier not found 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(190) : error C2872: 'assertion' : ambiguous symbol 1> could be 'boost::assertion' 1> or 'c:\libraries\boost_1_46_0\boost\spirit\home\classic\error_handling\exceptions.hpp(187) : boost::spirit::classic::assertion' 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(190) : error C2872: 'assertion' : ambiguous symbol 1> could be 'boost::assertion' 1> or 'c:\libraries\boost_1_46_0\boost\spirit\home\classic\error_handling\exceptions.hpp(187) : boost::spirit::classic::assertion' 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(190) : error C2872: 'assertion' : ambiguous symbol 1> could be 'boost::assertion' 1> or 'c:\libraries\boost_1_46_0\boost\spirit\home\classic\error_handling\exceptions.hpp(187) : boost::spirit::classic::assertion' 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(190) : error C2872: 'assertion' : ambiguous symbol 1> could be 'boost::assertion' 1> or 'c:\libraries\boost_1_46_0\boost\spirit\home\classic\error_handling\exceptions.hpp(187) : boost::spirit::classic::assertion' 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(190) : error C2882: 'assertion' : illegal use of namespace identifier in expression 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(190) : error C3861: 'expect_value': identifier not found 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(191) : error C2872: 'assertion' : ambiguous symbol 1> could be 'boost::assertion' 1> or 'c:\libraries\boost_1_46_0\boost\spirit\home\classic\error_handling\exceptions.hpp(187) : boost::spirit::classic::assertion' 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(191) : error C2872: 'assertion' : ambiguous symbol 1> could be 'boost::assertion' 1> or 'c:\libraries\boost_1_46_0\boost\spirit\home\classic\error_handling\exceptions.hpp(187) : boost::spirit::classic::assertion' 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(191) : error C2872: 'assertion' : ambiguous symbol 1> could be 'boost::assertion' 1> or 'c:\libraries\boost_1_46_0\boost\spirit\home\classic\error_handling\exceptions.hpp(187) : boost::spirit::classic::assertion' 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(191) : error C2872: 'assertion' : ambiguous symbol 1> could be 'boost::assertion' 1> or 'c:\libraries\boost_1_46_0\boost\spirit\home\classic\error_handling\exceptions.hpp(187) : boost::spirit::classic::assertion' 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(191) : error C2882: 'assertion' : illegal use of namespace identifier in expression 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(191) : error C3861: 'expect_escape': identifier not found 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(195) : error C3861: 'expect_object': identifier not found 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(196) : error C3861: 'expect_eoi': identifier not found 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(203) : error C3861: 'expect_objclose': identifier not found 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(209) : error C3861: 'expect_name': identifier not found 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(210) : error C3861: 'expect_colon': identifier not found 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(211) : error C3861: 'expect_value': identifier not found 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(218) : error C3861: 'expect_arrclose': identifier not found 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(224) : error C3861: 'expect_value': identifier not found 1>c:\libraries\boost_1_46_0\boost\property_tree\detail\json_parser_read.hpp(250) : error C3861: 'expect_escape': identifier not found 1>Build log was saved at "file://c:\Users\Steve\Documents\Visual Studio 2005\Projects\Error\Debug\BuildLog.htm" 1>Error - 57 error(s), 0 warning(s) ========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

2 1

lambda : fabs( x - y )< eps
by er 12 Mar '11

12 Mar '11

I'm submitting this in case someone easily spots a less verbose representation of fabs( x - y )< eps than the one shown below and would like to share it. Using lambda (or variants) only (I know I can write my own functor class). Thanks. #include <cmath> #include <boost/function.hpp> #include <boost/lambda/bind.hpp> #include <boost/lambda/lambda.hpp> #include <boost/numeric/conversion/bounds.hpp> typedef boost::function<double(double)> f1_; typedef boost::function<double(double, double)> f2_; typedef boost::function<bool(double)> g_; double eps = boost::numeric::bounds<double>::smallest(); f2_ f2 = lambda::bind( f1_( fabs ), lambda::_1 - lambda::_2 ) ; g_ g = ( eps > lambda::_1 ); BOOST_ASSERT( lambda::bind( g, lambda::bind( f2, lambda::_1, lambda::_2 ) )( 0.0, 0 * eps ) ); BOOST_ASSERT( !lambda::bind( g, lambda::bind( f2, lambda::_1, lambda::_2 ) )( 0.0, eps ) );

3 3

[range] strange behaviour with range-based for loop and adaptors
by Nathan Ridge 12 Mar '11

12 Mar '11

Hello, I am experiencing some strange behaviour when using adaptors with a range-based for loop. Here's what I'm trying: #include <vector> #include <iostream> #include <boost/foreach.hpp> #include <boost/range/adaptor/transformed.hpp> std::vector<int> f() { return std::vector<int>{1, 2, 3, 4}; } int add1(int x) { return x + 1; } int main() { for (int i : f() | boost::adaptors::transformed(add1)) std::cout << i << ' '; std::cout << '\n'; } The output is 1 3 4 5, instead of the 2 3 4 5 that I would expect. Is there something funny going on with temporaries? Does the temporary returned by f() not stick around for the duration of the loop? Thanks, Nate.

2 1

cyl_bessel_j performance
by Matwey V. Kornilov 12 Mar '11

12 Mar '11

Hi, cyl_bessel_j is several times slower than jn from glibc for me. What do I do wrong? Bessel function from boost.math seems to be pretty good coded and optimized but in a runtime it baffles me.

2 3

[proto] Object got sliced when passed by reference
by Leon Sit 12 Mar '11

12 Mar '11

Hi all I have a class tree as the following template<typename T> struct base{ bool operator()(int i)const { return static_cast< const T&>(*this)(i); } }; struct F1:public base<F1>{ bool operator()(int i) const{ return true; } }; struct F2:public base<F2>{ bool operator()(int i) const{ return true; } }; struct F3 :public base<F3>{ std::string junk_; F3(std::string junk):junk_(junk){} bool operator()(int i) const{ std::cout << junk_ << std::endl; return false; } }; ================================================================== I am trying to use proto to derive the following systax Predicate<F1> f1; Predicate<F2> f2; Predicate<F3> f3("hodqhoqw"); cout << ((f1||f2)&&f3)(1) << endl; ================================================================== When proto get to the point of invoking the F3::operator(), the junk_ attribute got sliced away. I thought I am passing everything by constant reference but the exception tells me otherwise. The full sample code is attached, can someone tell me what I have missed? I am testing my code on vc9 and vc10, and I am not using virtual function for performance issue. Ultimately, I want to have the following syntax in the client code F1 f1; F2 f2; F3 f3("hodqhoqw"); cout << ((f1||f2)&&f3)(1) << endl; Thanks

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a question about boost::serialization
by 547880119 12 Mar '11

12 Mar '11

i am wondering how boost distinguish array and pointer serializatoin. although i have read the source code of boost. but i cannot understand it well. so, can anyone explain it to me ? thank you very much. Ps:I want to know how does is_pointer< T > work. ------------------ Hello, I'm HillBoREDy.

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Re: [Boost-users] [xint] a bug in operator>> (was: Boost.XInt formal review)
by Riccardo Murri 12 Mar '11

12 Mar '11

Hello, I wanted to do some testing of XInt for the review, so I thought I could try it with a gaussian elimination code that I'm working on. I only had a quick glance at the library; the documentation seems very clear and my code compiled fine with Boost.XInt at the first attempt, just by changing one typedef. I'd like to join Christofer Jefferson in his praise of the work done for making XInt easy to use. However, running it seemed to take forever. After a while I traced this down to the following bug: * a very simple I/O program that works with std integral types: $ cat a.cpp #include <iostream> int main(void) { int i; long x; while (not std::cin.eof()) { std::cin >> i >> x; std::cout << "Read i:" << i << ", x:" << x << std::endl; if (0 == i and 0 == x) break; }; return 0; } $ c++ a.cpp -I ~/sw/include/ $ ./a.out 1 2 Read i:1, x:2 0 0 Read i:0, x:0 * the same simple program fails and goes in a busy-loop cycle with XInt: $ cat a.cpp #include <iostream> #include <boost/xint/integer.hpp> int main(void) { int i; boost::xint::integer x; while (not std::cin.eof()) { std::cin >> i >> x; std::cout << "Read i:" << i << ", x:" << x << std::endl; if (0 == i and 0 == x) break; }; return 0; } $ c++ a.cpp -I ~/sw/include/ $ ./a.out 1 2 Read i:1, x:0 Read i:1, x:0 Read i:1, x:0 <repeats ad libitum in a busy loop> For the record, I've tried gcc 4.4.3 on Ubuntu 10.04, with Boost 1.45.0 plus XInt (from the .zip file). Unofrtunately, this prevented all my computational jobs from getting to do any number crunching (they have been stalled into the read cycle for hours before I noticed). I would like to see XInt accepted based on its simplicity of use, but in the event I really did not test anything in the library except compilation. Best regards, Riccardo

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