February 2014 - Boost-users - lists.preview.boost.org

Apology: RE: FileSystem: crash on OSX 10.8 with create_directory
by Tim Burgess 08 Feb '14

08 Feb '14

Hi, I must apologise for the stupidity of this question - if I'd have surrounded the call with a try/catch block I'd have figured it out sooner, so it's my own bad coding. Now all I need to figure out is how to programmatically create a directory with admin rights to get around the permission denied exception when trying to create files/directories within /library/application support/ on the Mac. Best wishes. Tim Burgess From: Boost-users [mailto:boost-users-bounces@lists.boost.org] On Behalf Of Tim Burgess Sent: 07 February 2014 16:32 To: boost-users list Subject: [Boost-users] FileSystem: crash on OSX 10.8 with create_directory Hi, My app crashes out when I run the following: boost::filesystem::path myPath = wxStandardPaths::Get().GetConfigDir().ToStdWstring(); if (myPath.has_filename()) { myPath.remove_filename(); } // Add the company name and check for directory existence myPath /=wstrRBCompanyName; if (!boost::filesystem::exists(myPath)) { // The following test displays the path I'd expect to see (/library/Raised Bar in my case) wxMessageBox( myPath.native(), wstrErrorTitle, wxOK | wxICON_EXCLAMATION); // Create the required directory - displays a message box indicating deletion of a lock file here and the app exits boost::filesystem::create_directory(myPath); } This code appears to work fine on Windows, but fails on OSX 10.8. I should point out that I'm a blind programmer and I'm struggling to get Apple's VoiceOver utility to interact in a useful manner with Xcode 5's debugger and that's why I'm using a wxMessageBox to try and track down my failure. Best wishes. Tim

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Generating PDF from QuickBook?
by Nat Goodspeed 08 Feb '14

08 Feb '14

I'm sorry, this must be a FAQ, but my Google search turned up mail from 2009 advising me to cd to libs/xxx/doc and run ../../../b2 pdf When I do that in a new modular Boost tree, I get the following errors: /Users/nat/boost-git/tools/build/src/tools/boostbook.jam:704: in construct from module object(boostbook-target-class)@1466 error: Cannot build documentation type 'pdf'. /Users/nat/boost-git/tools/build/src/build/targets.jam:1332: in class(a)basic-target.generate from module object(boostbook-target-class)@1466 /Users/nat/boost-git/tools/build/src/build/targets.jam:757: in generate-really from module object(main-target)@1471 /Users/nat/boost-git/tools/build/src/build/targets.jam:729: in class(a)main-target.generate from module object(main-target)@1471 /Users/nat/boost-git/tools/build/src/build/targets.jam:272: in class(a)project-target.generate from module object(project-target)@1460 /Users/nat/boost-git/tools/build/src/build-system.jam:707: in load from module build-system /Users/nat/boost-git/tools/build/src/kernel/modules.jam:289: in import from module modules /Users/nat/boost-git/tools/build/src/kernel/bootstrap.jam:139: in boost-build from module /Users/nat/boost-git/boost-build.jam:17: in module scope from module Is there some incantation I can apply to produce PDF output?

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Confused with the example students_t_single_sample.cpp
by lizy10b 08 Feb '14

08 Feb '14

Hi there, I got a problem with the example "students_t_single_sample.cpp". The corresponding document is at: http://www.boost.org/doc/libs/1_55_0/libs/math/doc/html/math_toolkit/stat_t… Actally, I am confused with the mathematical logic rather than coding. The document presents a table that shows four hypothesis and tests, I am OK with the frist two, but for the third and the fourth ones: The original text: Hypothesis 3: the sample mean is less than the true mean Test 3: Reject if CDF of t > significance level, cdf(dist, t) > alpha I think p-value should be the integral from t to +Infinite: cdf(complement(dist, t)), So reject Hypothesis 3 when cdf(complement(dist, t)) < alpha, or say cdf(dist, t) > 1-alpha The original text: Hypothesis 4: the sample mean is greater than the true mean Reject if complement of CDF of t > significance level: cdf(complement(dist, t)) > alpha Similarly, the p-value should be the integral from -Infinite to t: cdf(dist, t), so reject Hypothesis 4 when cdf(dist, t) < alpha Is that right? Thanks. Zhiyu Li 2014-01-11 lizy10b

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Newbie math question - roots of a distribution
by Benjamin Ward (ENV) 08 Feb '14

08 Feb '14

Hi Boost list, I've just installed and started to use boost for various problems and I've hit on a math problem I'd like to solve with it but I'm unsure on how to achieve it. I've gone through the documentation and have worked out how to easily compute the value from a cdf of a binomial distribution: #include <boost/math/distributions/binomial.hpp> #include <iostream> int main(){ int numbertrials = 4164; double successprob = 10e-6; int numbersuccesses = 75 boost::math::binomial mydistribution(numbertrials, successprob); double ans = cdf(mydistribution, numbersuccesses); std::cout << "The answer is " << ans << std::endl; return 0; } But now I'd like to find the root of the cdf, in other words, I want to find the value of successprob, from numbertrials and numbersuccesses and ans. Let's define ans as 0.95, by finding the root of cdf(mydistribution, numbersuccesses) - 1, using a root finding algorithm, I should be able to get the value of successprob. I've tried reading the roots documentation and looking at some examples but they use simple functions like x * sin(x) - there is only one variable and it is x, the binomial cdf has quite a few variables - number of trials, number of successes, probability of a single success. How can I define a function with boost::math::binomial that could be used with boosts root libraries to find the probability of success from the cdf, given I know ans, the number of successes, and the number of trials? Thanks, Ben W.

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intrusive data structures with custom pointer class
by Matei David 07 Feb '14

07 Feb '14

Hi, I would like to use some boost::intrusive data structures (lists and trees) in a project I'm working on, but I ran into trouble trying to customize the existing classes to my needs. I decided to post my problem here, in case somebody knowledgeable of boost::intrusive *implementation details* can assist me. Thank you in advance. Background: In the project I'm working on, I need to manage a large number of objects in memory. The data is dynamic, so I need to be able to alloc&dealloc objects, in addition to keeping the objects in various lists&trees (for which I'm trying to use boost::intrusive). The RAM usage is large (think, >100GB), but the number of objects is smaller than 2^32. So one thing I'd like to do is to replace 8-byte raw pointers with 4-byte offsets into a deque. Doing this would solve the alloc/dealloc part. However, I now need to customize boost::intrusive containers to work with these 4-byte offsets instead of raw pointers. Initial solution that doesn't work: The most important limitation of these 4-byte indirect pointers (say to a type T) is that if you fully dereference one to T&, you can no longer reconstruct the indirect pointer (with operator&) in constant time. I.e. converting a real-pointer to indirect-pointer must be avoided. Thus, to make methods such as insert(T&) work, I had to roll out a reference-replacement class in addition to the pointer-replacement class. This is what I initially tried: - Given a type T, I rolled out pointer-replacement class Ptr<T> which holds a 4-byte int, and upon operator*, it produces a Ref<T> object. - A reference-replacement Ref<T> class similarly holds a 4-byte int, it implements operator& which produces the associated Ptr<T> object, and it also provides an operator T& () conversion which dereferences the object from the deque. - With these, I tried a custom traits struct looking like this: value_type = node := T node_ptr = pointer := Ptr<T> reference := Ref<T> Problems: Even though intrusive data structures are designed with the stated goal of leaving memory management to the user, intrusive lists&trees do allocate one extra node object that they use as "header". The code then takes the address (&) of this node and uses it in comparisons as a node_ptr. Because of this, my custom traits above could not compile. The only way I could find to make such containers work for my needs is basically a hack: define "node" to be a "pointer holder" object (neither member nor base of "value"), that allocates a "value" struct from the deque upon construction, that responds to operator& by returning the held pointer, and that otherwise acts as a value&. From what I could gather reading the docs, boost::intrusive containers allow some type of customization via the traits structs. However, I see some drawbacks: A. The traits classes seem to be there to support 2 existing customization types, namely the situation where "node" is a base class of "value" (implementing "base hooks") and the situation where "node" is a member of "value" (implementing "member hooks"). My situation represents a 3rd customization type. B. Even though the traits classes allow one to specify pointer types, it's possible (?) that under the hood the classes were designed to support only raw pointers and smart pointers, not the indirect offset-like pointers I need. Given A&B, it seems to me that in my customization I would need 2 different hacks. In the interest of code stability, I started wondering whether it is feasible to adapt existing boost::intrusive data to my needs (my first instinct) as opposed to simply rolling out my own rbtree. Questions: 0. Obviously: Have you seen a similar situation being dealt with before? Maybe there's an existing solution out there. My reluctance to rolling out my own intrusive rbtrees is due to the fact I'd have to test them, as opposed to using a known implementation. 1. Are boost::intrusive data structures supposed to support custom pointer classes (neither real pointers nor smart pointers)? For instance, in 1.46 I found this code in boost/intrusive/detail/tree_algorithms.hpp static node_ptr uncast(const_node_ptr ptr) { return node_ptr(const_cast<node*>( ::boost::intrusive::detail::boost_intrusive_get_pointer(ptr))); } So despite all the custom traits structs defining node_ptr and const_node_ptr, under the hood you have a line of code which assumes node_ptr can be constructed from node*. This is the expensive real-pointer to offset-pointer no-no I mentioned earlier. However, intrusive lists worked just fine in 1.46, which suggests this was simply a bug. 2. Can you point me to an example of defining and using custom pointer class with boost::intrusive? To enable compilation (of lists only) in 1.46, I had to customize std::iterator_traits (that part I understood), but then also boost::pointer_to_other and boost::intrusive::detail::smart_ptr_type. Even though the code compiled, I don't know what those are doing exactly, so I'm weary of them. 3. In 1.55, I have a few more pages of errors, I think mainly due to these pointer customization issues I don't fully understand. Something seems to have changed from 1.46 to 1.55. Is there a reference about what changed? Or is there a portable way of rolling out such a custom pointer class? Many thanks, M

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BOOST Spirit Qi and lexer parsing of tokens
by Howard, Tony 07 Feb '14

07 Feb '14

Hi, I am starting a project that will use spriti Qi and a lexer. I am having difficulty getting something simple to parse correctly without having to add states and just want to make sure I am going about it the right way. I have a label that should parse the following example (where the label starts/ends with a single quote): 'this is my BOOLEAN 123label 12as' And then this label will be followed by zero or more blanks and then a number enclosed in parenthesis: ( 123 ) There are a number of arbitrary blanks in between the number and the enclosing parenthesis. I am ignoring blanks and whitespace in the default state of the lexer (assume blanks and white spaces are defined in the patterns referenced): this->self += lex::token_def<>("{BLANK}")[ lex::_pass = lex::pass_flags::pass_ignore ]; this->self += lex::token_def<>("{WS}")[ lex::_pass = lex::pass_flags::pass_ignore ]; The first problem I encountered was that if I ignored blanks in the initial state and tried to parse a label that contains blanks that I don't want to ignore, this was not possible. So I had to create a label state, to which the blank token is added, and am switching to this state initially using in_state[...] so that when we are done with the label, we return to the initial state, where blanks are once again ignored. This worked. The problem then came with the digits. Since the digits were already recognized in the label state, I could not also recognize them in the initial state. So I added a digit state, where the digit token is now defined and the label state has to transition to this state while parsing between letter, symbols and digits (and whatever else I decide is allowed to make up my label), and after I get out of the label state, my rule parses a parenthesis, goes into the digit state, and then parses the closing parenthesis. This works correctly for what I need now. The issue I am having is looking ahead. What if a rule needs lower case letters only? I will have to create a state for it, remove it from the label state, etc. I will have to do this for any core patterns, which to me seems like there should be an easier way to do this. Any suggestions, comments, concerns? I have code snippets if my approach is not clear. Thanks for your help. Tony.

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FileSystem: crash on OSX 10.8 with create_directory
by Tim Burgess 07 Feb '14

07 Feb '14

Hi, My app crashes out when I run the following: boost::filesystem::path myPath = wxStandardPaths::Get().GetConfigDir().ToStdWstring(); if (myPath.has_filename()) { myPath.remove_filename(); } // Add the company name and check for directory existence myPath /=wstrRBCompanyName; if (!boost::filesystem::exists(myPath)) { // The following test displays the path I'd expect to see (/library/Raised Bar in my case) wxMessageBox( myPath.native(), wstrErrorTitle, wxOK | wxICON_EXCLAMATION); // Create the required directory - displays a message box indicating deletion of a lock file here and the app exits boost::filesystem::create_directory(myPath); } This code appears to work fine on Windows, but fails on OSX 10.8. I should point out that I'm a blind programmer and I'm struggling to get Apple's VoiceOver utility to interact in a useful manner with Xcode 5's debugger and that's why I'm using a wxMessageBox to try and track down my failure. Best wishes. Tim

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Build: Clang, libstdc++ and Mac 10.8
by Tim Burgess 07 Feb '14

07 Feb '14

Hi, Due to the requirements of another library I have to use, I need to build Boost 1.55.0 on my Mac 10.8 system using the libstdc++ STL library, rather then libc++. I've now got myself royally confused with the build configuration process, as to where I specify toolsets and other options to achieve what I need. I'm failing with: Cd /users/tim/developer/libraries/boost_1_55_0 ./b2 clean sudo sh bootstrap.sh macosx-version=10.8 macosx-version-min=10.7 architecture=combined threading=multi link=static address-model=32_64 ./b2 toolset=clang -std=c++11 cxxflags="-stdlib=libstdc++" linkflags="-stdlib=libstdc++" I don't actually need the c++11 support. Can anybody advise, please? Best wishes. Tim Burgess

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lexical_cast: fatal error
by Tim Burgess 07 Feb '14

07 Feb '14

Hi, Using 1.55.0 in my Xcode project with clang as the compiler I'm getting: "/boost/type_traits/is_fundamental.hpp:26:20: fatal error: recursive template instantiation exceeded maximum depth of 128"::boost::is_arithmetic<T>::value This error is triggered by me including lexical_cast.hpp. Has anybody else encountered this and, if so, found a solution, please? Best wishes. Tim Burgess

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Boost Accumulators Tail
by Jon Lederman 06 Feb '14

06 Feb '14

Hi, I am a newbie to using boost accumulators. I have tried a simple program using examples from the boost website. I have something as simple as: #include <boost/accumulators/accumulators.hpp> #include <boost/accumulators/statistics/stats.hpp> #include <boost/accumulators/statistics/tail.hpp> include <boost/accumulators/statistics/tail_quantile.hpp> using namespace boost::accumulators; typedef accumulator_set<double, stats<tag::tail_quantile<right> > > accumulator_t_right; typedef accumulator_set<double, stats<tag::tail_quantile<left> > > accumulator_t_left; accumulator_t_right acc0( tag::tail<right>::cache_size = 1000 ); accumulator_t_right acc1( tag::tail<right>::cache_size = 1000 ); accumulator_t_left acc2( tag::tail<left>::cache_size = 1000 ); accumulator_t_left acc3( tag::tail<left>::cache_size = 1000 ); I am met with: /usr/local/src/freeswitch/src/mod/applications/mod_soundtouch/mod_soundtouch.cpp:56:63: error: template argument 1 is invalid /usr/local/src/freeswitch/src/mod/applications/mod_soundtouch/mod_soundtouch.cpp:56:65: error: template argument 1 is invalid /usr/local/src/freeswitch/src/mod/applications/mod_soundtouch/mod_soundtouch.cpp:56:67: error: template argument 2 is invalid /usr/local/src/freeswitch/src/mod/applications/mod_soundtouch/mod_soundtouch.cpp:56:88: error: invalid type in declaration before ';' token /usr/local/src/freeswitch/src/mod/applications/mod_soundtouch/mod_soundtouch.cpp:57:62: error: template argument 1 is invalid /usr/local/src/freeswitch/src/mod/applications/mod_soundtouch/mod_soundtouch.cpp:57:64: error: template argument 1 is invalid /usr/local/src/freeswitch/src/mod/applications/mod_soundtouch/mod_soundtouch.cpp:57:66: error: template argument 2 is invalid /usr/local/src/freeswitch/src/mod/applications/mod_soundtouch/mod_soundtouch.cpp:57:86: error: invalid type in declaration before ';' token /usr/local/src/freeswitch/src/mod/applications/mod_soundtouch/mod_soundtouch.cpp:59:42: error: template argument 1 is invalid /usr/local/src/freeswitch/src/mod/applications/mod_soundtouch/mod_soundtouch.cpp:59:56: error: expected unqualified-id before '=' token /usr/local/src/freeswitch/src/mod/applications/mod_soundtouch/mod_soundtouch.cpp:60:42: error: template argument 1 is invalid /usr/local/src/freeswitch/src/mod/applications/mod_soundtouch/mod_soundtouch.cpp:60:56: error: expected unqualified-id before '=' token /usr/local/src/freeswitch/src/mod/applications/mod_soundtouch/mod_soundtouch.cpp:61:41: error: template argument 1 is invalid /usr/local/src/freeswitch/src/mod/applications/mod_soundtouch/mod_soundtouch.cpp:61:55: error: expected unqualified-id before '=' token /usr/local/src/freeswitch/src/mod/applications/mod_soundtouch/mod_soundtouch.cpp:62:41: error: template argument 1 is invalid /usr/local/src/freeswitch/src/mod/applications/mod_soundtouch/mod_soundtouch.cpp:62:55: error: expected unqualified-id before '=' token Do I need to use a specific namespace for the right and left arguments? Where are these defined? Or is something else wrong. Any help would be greatly appreciated. Thank you in advance. Regards, Jon

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Building Boost dynamically linkable gives linking error?
by Mehmet Emin Erük 06 Feb '14

06 Feb '14

I am trying to build boost and generate dll's but whatever I have done did not solve the problem. Here what I have got: Creating library bin.v2\libs\thread\build\msvc-11.0\dbg\adrs-mdl-32\async-excpt-on\thrd-mlt\boost_thread-vc110-mt-gd-1_53.lib and object bin.v2\libs\thread\build\msvc-11.0\dbg\adrs-mdl-32\async-excpt-on\thrd-mlt\boost_thread-vc110-mt-gd-1_53.exp thread.obj : error LNK2019: unresolved external symbol "__declspec(dllimport) public: __thiscall boost::gregorian::greg_month::greg_month(unsigned short)" (__imp_??0greg_month@gregorian@boost@@QAE@G@Z) referenced in function "public: __thiscall boost::gregorian::date::date(enum boost::date_time::special_values)" (??0date@gregorian@boost@@QAE@W4special_values@date_time@2@@Z) thread.obj : error LNK2019: unresolved external symbol "__declspec(dllimport) public: __thiscall boost::gregorian::greg_month::operator unsigned short(void)const " (__imp_??Bgreg_month@gregorian@boost@@QBEGXZ) referenced in function __catch$?make_external_thread_data@?A0x9b8c45f0@boost@@YAXXZ$0 bin.v2\libs\thread\build\msvc-11.0\dbg\adrs-mdl-32\async-excpt-on\thrd-mlt\boost_thread-vc110-mt-gd-1_53.dll : fatal error LNK1120: 2 unresolved externals Here some information about the setup: OS: W7 x64 Command to build: b2 -j%NUMBER_OF_PROCESSORS% --abbreviate-paths toolset=msvc-11.0 define=_SECURE_SCL=0 define=_CRT_SECURE_NO_DEPRECATE define=_CRT_SECURE_NO_WARNINGS --without-mpi address-model=32 variant=debug install link=shared runtime-link=shared threading=multi asynch-exceptions=on exception-handling=on extern-c-nothrow=off --prefix=..\boost cd .. I have CYGWin installed to the computer. *Here what I have tried till now;* *I have tried to build it in 32 bit command window (I am using jenkins to build boost) <tns:build tns:position='boost/boost_1_53_0' tns:command='C:\Windows\SysWOW64\cmd /C bootstrap.bat'/> <tns:build tns:position='boost/boost_1_53_0' tns:command='C:\Windows\SysWOW64\cmd /C build_boost-win32-debug-vs2012.cmd'/> *I wrote #define BOOST_ALL_DYN_LINK in the boost config/user.hpp *I wrote #define BOOST_ALL_NO_LIB in the boost config/user.hpp Is there anyone who experienced such a problem before? I really could not find anything in anywhere? -- bir gün herkes özgür olacak

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[Move, Container] returning a move-only type
by John M. Dlugosz 05 Feb '14

05 Feb '14

The definition of boost::container::vector includes: BOOST_COPYABLE_AND_MOVABLE rather than BOOST_MOVABLE_BUT_NOT_COPYABLE if the element type cannot be copied. If I have: typedef boost::container::vector<MyType> VecType; VecType foo() { ⋮ return boost::move(some_other_vec); } VecType x= foo(); On a configuration with BOOST_NO_RVALUE_REFERENCES defined, this gives an error within VecType's copy constructor, since MyType cannot be copied. If I write VecType x= boost::move(foo()); then I get an error that no matching move is viable, as the move(T&) wants an lvalue as the argument. I can't write the return type of foo to be rv<VecType> because that can't be copied (fake move-out like auto_pointer) either; the members are declared private and never defined. I'm thinking that if VecType were BOOST_MOVABLE_BUT_NOT_COPYABLE then it would work as expected, since operator rv<VecType>& would be provided. How can I make this work without surgery on the Boost headers, and hopefully without something ugly like deriving from vector and having to re-define and forward all the various constructors and such? —John

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[Range, Container] range of to-be-moved values ?
by John M. Dlugosz 05 Feb '14

05 Feb '14

Given a boost::container::vector<C> vec; I can write vec.push_back(move(value)) for a move-only (non-copyable) type C, instead of vec.push_back(value) as usual. But what would I write instead of vec.insert(pos,b,e) where (b,e] is a range of values? I'm particularly fond of Range concept, rather than loose iterators, so my function would be something that takes something that works as a Range; e.g. template <typename R> void prepend (const R& src_range) { auto b= boost::begin(src_range); auto e= boost::end(src_range); vec.insert(vec.begin(), b, e); } An rvalue reference to a range is not the same thing as a range of values that I may move from. I could have a differently named function and pass it a range with the implicit assumption that the function will modify the values, but is there a proper way to indicate that as part of the type? src_range can be, say, a pair of (non-const) iterator s as opposed to a pair of const_iterator s, or otherwise range_iterator<R>::type is dereferencable to a const value or not. But that itself is hard to see in general let alone overload against! If my function were called prepend_and_destroy_original(src) it might clue in the caller, but in general it is surprising that a parameter of (const R&) will modify the values. src itself doesn't change, and now refers to the same range of values which are now swapped out with defaults. With built-in pointers and even shared_ptr I can distinguish between an in-out parameter and a parameter that dereferences to a modifiable or const value. But what about with Ranges? Even with lower-case ranges provided by two iterators, How can you call something like boost::container::vector v2 (InIt_start, InIt_end); to convert a std::vector or some other container of move-only items? Only if the types match exactly can the vector(vector&&) constructor be used. —John

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[iostreams] Why does boost::iostreams::copy close the Sink & Source?
by Sebastian Karlsson 05 Feb '14

05 Feb '14

What's the rationale behind this decision? I don't find it intuitive and reduces the utility of the function. In my case I read from a file into a stream which I want to later use, the signature of the device is important. But as soon as I've copied my data over to the device it's destroyed and along side the data goes down the drain. Kind regards, Sebastian Karlsson

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Boost.MultiIndex. Using several keys together.
by syvyi 05 Feb '14

05 Feb '14

Hello, there's a structure struct person { std::string name; std::string surname; int birth_year; std::string craft; }; How to create such a multiindex container that dumping could performed using an index as name, surname and year triple alltogether? -- View this message in context: http://boost.2283326.n4.nabble.com/Boost-MultiIndex-Using-several-keys-toge… Sent from the Boost - Users mailing list archive at Nabble.com.

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boost::python wrapping a container of boost::variant?
by Mario Lang 05 Feb '14

05 Feb '14

Hi. Does anyone have ideas how to convince boost::python to wrap a container of boost::variant? I need this to generate useful python bindings for a project of mine which uses boost::variant internally. Since python supports heterogenous containers natively, it seems to me this should be doable. However, I have attempted to find a solution on my own on several occasions, and always failed. One obvious hint is the indexing_suite. However, now that I looked at it again, I think I know where the problem is: The get_item method of indexing_suite always returns a data_type object, which is value_type from the container in question. However, from what I can see, I'd need something that converts to boost::python::object, so that I can return whatever class is appropriate for the actual variant instance. In other words, get_item would need to return a boost::python::object instead of data_type. To illustrate in code what I want, here is a minimal example: #include <boost/python.hpp> #include <boost/variant.hpp> struct a { int x; }; struct b { double y; }; typedef boost::variant<a, b> variant; typedef std::vector<variant> vector; BOOST_PYTHON_MODULE(bpv) { using namespace boost::python; class_<a>("a", init<a>()) .def(init<>()) .def_readonly("x", &a::x); class_<b>("b", init<b>()) .def(init<>()) .def_readonly("y", &b::y); } The question is, how do I expose std::vector<variant> to Python? I guess I need to define a static_visitor that returns python objects, something like: struct to_python_visitor : boost::static_visitor<boost::python::object> { result_type operator()(a const &a_) const { // return a boost::python::object that refers to a_ } ... }; And hook that up to the container support somehow such that boost::apply_visitor(to_python_visitor(), variant_instance) is called whenever a value is retrieved from the container. Can this even be done with current Boost.Python? Any hints, maybe even concrete code examples, would be highly appreciated. -- CYa, ⡍⠁⠗⠊⠕

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boost::none for boost::shared_ptr
by Chris Stankevitz 03 Feb '14

03 Feb '14

Hello, Does boost::shared_ptr offer a way to create an empty shared pointer without a lot of typing? Perhaps something analogous to boost::none. I am not using c++11. Thank you, Chris == using boost::none; using boost::optional; // declare f(optional<CSomeReallyLongClassName> Item); g(shared_ptr<CSomeReallyLongClassName> pItem); // invoke f with empty object f(none); // invoke g with empty object g(shared_ptr<CSomeReallyLongClassName>());

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multi_array move semantics
by MM 03 Feb '14

03 Feb '14

Hello, 1. Browsing the multi_array doc, there doesn't seem to be a move ctor? 2. Has there been any attempt to implement one? 3. if not, and the authors are reading this, are there any hints to help with this? Regards MM

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serialization: intrusive_ptr
by MM 03 Feb '14

03 Feb '14

Hello, I've found an implementation of a serializer for intrusive_ptr here: http://stellar.cct.lsu.edu/files/hpx_0.9.5/html/code/hpx/util/serialize_int… which i've injected into my boost lib. Hartmut Kaiser, I guess, would there be a proposal to add it serialization for future standard boost? Regards MM

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