July 2012 - Boost-users - lists.preview.boost.org

[Phoenix] for_each calling push_back for stl containers
by Ryan 17 Jul '12

17 Jul '12

Hello, In upgrading from boost 1.39 to 1.47 I changed my use of the Phoenix library (which was within Spirit) to the stand alone Phoenix library. This caused my below code to stop working. /**** Code Start ***/ static boost::char_separator<char> seperator(":"); boost::tokenizer< boost::char_separator<char> > tokens(s, seperator); //s is a passed in std::string std::vector<std::string> string_tokens; namespace phx = boost::phoenix; //This line fails to compile now. std::for_each(tokens.begin(), tokens.end(), phx::bind(&std::vector<std::string>::push_back, &string_tokens, phx::arg_names::arg1)); /**** Code Stop ***/ This lead me to three questions. 1. What changed about phoenix bind that caused this not to work any more? 2. I tried using the lazy version of push_back to bypass the bind issue. In the documentation there are not any examples of multiple algorithm and container methods calling each other to show how the arguments of one method is passed to another. std::for_each(tokens.begin(), tokens.end(), phx::push_back(&string_tokens, phx::arg_names::arg1)); This compiles but nothing is placed into string_tokens. So I'm assuming the argument from for_each isn't being passed to push_back. What needs to changed in this method call? 3. Can that entire line of question 2 be replaced with the lazy version of the method calls or does the outer most call need to be a non-lazy method? phx::for_each(phx::arg_names::arg1, phx::push_back(phx::arg_names::arg2, phx::arg_names::arg3))(tokens, string_tokens, ???); If the entire line can be a lazy version then how would I map for_each to push_back for arg3? Any help for these three questions would really be appreciated. Ryan

5 23

How to deal with the exception " End of File"
by mcheng 17 Jul '12

17 Jul '12

Hi all: I have check the thread which was talking about "end of file" problem. I have the same issue and I have no idea about when the socket be closed by program. The author said that he fixed the bug after debugging finally but he didn't show the way to solve the problem and where was the bug is~ Can some body give me some hint about it ? Thanks Cheer~ Cheng Mo Beijing Jaeger Communication Electronic Technology Co., Ltd. Addr: Floor2B Dingjun Plaza No.75 Suzhou Street, 100080, Beijing, China Mail: mcheng(a)pbicn.com

2 1

[context] Release date?
by Szymon Gatner 17 Jul '12

17 Jul '12

Hey, boost.context has been accepted quite some time ago, is there any eta on when it is going be officially part of boost? asio (for async task running) + context (as a coroutine/continuation) == pure win -- Szymon Gatner The Lordz Games Studio www.thelordzgamesstudio.com

3 6

compile asio against static boost libs
by Sergiy Nazarenko 17 Jul '12

17 Jul '12

Hi all! I would like to compile my project against static libraries If I compile my project in following manner: c++ -I/usr/local/include/boost/1.49.0/ -c -o azio.o azio.cpp c++ -L/usr/local/lib64/boost/1.49.0/ azio.o -lboost_system -o bin/azio It is OK. But if I use static libraries: c++ -I/usr/local/include/boost/1.49.0/ -c -o azio.o azio.cpp c++ -L/usr/local/lib64/boost/1.49.0/ azio.o /usr/local/lib64/boost/1.49.0/libboost_system.a -o bin/azio I have got error: azio.o: In function `boost::asio::detail::posix_tss_ptr_create(unsigned int&)': azio.cpp:(.text._ZN5boost4asio6detail20posix_tss_ptr_createERj[boost::asio::detail::posix_tss_ptr_create(unsigned int&)]+0x19): undefined reference to `pthread_key_create' azio.o: In function `boost::asio::detail::posix_thread::~posix_thread()': ........ ........ boost::asio::detail::task_io_service::thread_info>::context>::operator=(boost::asio::detail::call_stack<boost::asio::detail::task_io_service, boost::asio::detail::task_io_service::thread_info>::context*)]+0x20): undefined reference to `pthread_setspecific' collect2: ld returned 1 exit status I used strings to know where is function pthread_key_create. I found in libboost_thread.so. Next my step was: c++ -L/usr/local/lib64/boost/1.49.0/ azio.o /usr/local/lib64/boost/1.49.0/libboost_system.a /usr/local/lib64/boost/1.49.0/libboost_thread.a -o bin/azio I've try out to mix up places libraries and object file c++ .. azio.o libboost_system.a libboost_thread.a -o bin/azio c++ .. libboost_system.a libboost_thread.a azio.o -o bin/azio c++ .. libboost_thread.a azio.o libboost_system.a -o bin/azio But error is still. Thanx, Sergiy

3 4

[boost] conversion review report
by Gordon Woodhull 16 Jul '12

16 Jul '12

Hi Vicente, all, Profuse apologies for the long delay in writing this report. Cheers, Gordon Report on Boost Conversion Library Review, August 20-29, 2011. I want to thank Vicente Botet Escriba for submitting the Conversion library for review and for his general good nature in receiving criticism and alternate designs. The Conversion library presents a general framework for plugging in conversion operations between arbitrary types, providing a consistent interface for type-to-type conversions. The library is unfortunately rejected. During the review, there were two votes for acceptance and two against, and some interesting conversation from about a dozen participants. The major reason the library can't be accepted in its current form is that there was near consensus that there is no universal conversion domain, especially when the source or destination type might be a string. Much of the review focused on possible One Definition Rule (ODR) violations, which are a consequence of having a universal customization point using template specializations or function overloads. Many solutions were offered, which will make up the second part of this report, "How to Avoid Universality." I. Concerns about the library Conversions Are Not Generic? While some reviewers didn't see the need for a generic conversion library (and I was a little surprised at the vehemence of their opinions), I don't see this in itself as a reason to reject the library. The library's stated purpose is to provide a common interface for general type <-> type conversions, like lexical_cast does for string <-> type conversions. However, it was interesting that seemingly no one could come up with applications of truly generic conversion, although Jeffrey Lee Hellrung and Antony Polukhin alluded to their existence. Also, some reviewers pointed out that you often need to choose what kind of conversion to do, and a generic library can get in the way here. Strings are the most obvious example: if you are converting from a string representing a binary value it would not work to use a decimal converter. Antony Polukhin pointed out a more subtle example: "lexical_cast<char>(1) and numeric_cast<char>(1) will produce different output." Jeff Hellrung summed this point up nicely: "I think it's certainly possible for different clients using the same generic component to want different conversion implementations for a given pair of types, and that point, Boost.Conversion's universally-defined conversion implementations become useless. One wants the conversion operation to be parametrized as well as the types involved in the conversion." Multi-Client Specialization Concerns Leaving aside possible ODR violations, which we'll return to in Part II, some reviewers questioned the scalability of using template specialization and overloads when many clients (i.e. independent headers) may be customizing the behavior. Vladimir Batov claimed that a system which allows partial specializations on both Source and Target can't be made to work generally. Jeroen Habraken said SFINAE/enable_if "does make code fragile". I'm not clear if these conversations were resolved (or resolvable ;). Non-Generic Solutions Some reviewers objected that conversions should just be defined within individual libraries, but of course this begs the question (as came up recently on the ML between DateTime and Chrono), "which library should house the conversions?" Others (such as Phil Endecott) thought that simple c-style functions such as rgb_to_cmyk() were more explicit and direct. Why is this so complex? Kevlin Henney, initially excited about a general solution to the problem which lexical_cast first set out, commented on the documentation: "Based on casual reading, it feels a little more complex and requires a higher-entry level of knowledge than would be appropriate for many of the people who actually need this functionality." II. How to Avoid Universality One of the positive results of this review was a small catalog of alternatives to a universal customization point involving template specialization or overloaded functions. a. Avoid the Problem In the strictest sense, any library which allows either kind of universal customization can be prone to ODR violations. But many reviewers particularly thought that a customization point involving two UDTs was especially dangerous. To his credit, Vicente was very up-front about the limitations of his design, and attempted to formulate rules for how the library could be used safely. In the documentation, he suggests (IIUC) that header-only libraries could use generic conversions as long as they don't define them, or define them as long as they don't use them. http://tinyurl.com/cmbgyfk b. Inherited tags John Bytheway suggested a tag-dispatch system where conversions are tagged with their source library, and any library which depends on conversions from two libraries would define a tag which inherits from the tags of both libraries. Thus ODR violations are avoided at the expense of having to specify an extra tag (effectively a sort of global conversion domain). http://lists.boost.org/Archives/boost/2011/08/184836.php c. Conversion Domains and Overloaded Function Objects Going on the consensus that there is no universal conversion domain, your humble review manager suggested a metaprogramming solution that defines conversion domain objects which combine a set of conversions within an object. http://lists.boost.org/Archives/boost/2011/08/185259.php A more general solution would be to create an overloaded polymorphic function object, much like a polymorphic-source version of Lorenzo Caminiti's OverloadedFunction library (http://tinyurl.com/72nolyj) However, I have been warned (by Daveed Vandevoorde) that the rules for function overloading are too dangerously complicated to implement in a metaprogram. d. Boost.Dispatch Matthias Gaunard announced that he is working on a library particularly to "solve the problem of specializing a function template for a category of types with best-match selection." http://lists.boost.org/Archives/boost/2011/08/185286.php e. Abuse of Unnamed Namespaces Emil Dotchevski suggested that "It might be possible to abuse unnamed namespaces to avoid violating ODR". I'm not clear if this was a serious suggestion as it wasn't spelled out. :) f. GIL's solution (?) Christian Henning wrote: "GIL has such functionality. I like their way of structuring conversion." However, I was not able to find a description of this mechanism for the report. Thanks to everyone who participated in the review! _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost

1 0

Re: [Boost-users] testing archive version of boost::serialize
by Sam Appleton 16 Jul '12

16 Jul '12

Hi Robert Thanks for replying. I realize perhaps I was not clear or do not fully understand your answer. I was not really looking for ways to test my archive class. Let's say I know I have an archive file that's been generated by my archival class, but it has an indeterminate version that may or may not be compatible with the present version. In order for me to determine the embedded version of the archive, the only way I know of is to just attempt to deserialize (I do this using (archive-stream) >> (object) ; ) and seeing if a version incompatability is flagged. However, is there any way to determine just from an open archive stream what the version number of the embedded stream or classes implied by the stream contains? Sam >Check the documentation section Reference/Archive Class Reference/Testing > >This explains how you can submit your archive class to the exhaustive >series of tests that all the "built-in" archives are subjected to. It does >take a while to run the tests. And then it makes even more time to >get your custom archive to pass all the tests. But you will be >rewarded with something you should be able to depend upon. > >Robert Ramey -- -- Sam Appleton CEO, Ausdia Inc. o: (408) 914 2704 x801 f: (408) 914 2704 c: (650) 242 2908 Email sam(a)ausdia.com Skype samsappleton

2 1

[1.50.0] PDF documentation available
by John Maddock 15 Jul '12

15 Jul '12

With apologies for being so late with these.... The PDF build of Boost's documentation for 1.50 is available from the usual SF site: https://sourceforge.net/projects/boost/files/boost-docs/1.50/ John.

2 1

testing archive version of boost::serialize
by Sam Appleton 14 Jul '12

14 Jul '12

Is there any way to "test" the version of a boost serialization archive. I know that we can always just attempt to deserialize and catch the generated exception, but is there any way to just test the version of the archive before attempting deserialization? Best Sam Appleton

2 1

aiso signal handling, daemon shutdown
by Kraus Philipp 13 Jul '12

13 Jul '12

Hello, I try to create a working example for a daemon with http://www.boost.org/doc/libs/1_50_0/doc/html/boost_asio/overview/signals.h… I have created a program like: static bool run = true; void handler( const boost::system::error_code& error, int signal_number) { if (!error) { run = false; std::cout << "signal" << std::endl; } } and the main with int main(..) { boost::asio::io_service io_service; boost::asio::signal_set signals(io_service, SIGINT, SIGTERM); signals.async_wait(handler); while (run) { boost::this_thread::yield(); } } The program runs, but if I do "kill pid" the program does not stop or shows the message. I would like to create a small daemon which runs some threads and can stop with the normal stop signal and can reload the configuration on reload. Can anyone help me to create a working example first !? Thanks a lot Phil

2 2

mult_array view question
by Petros 13 Jul '12

13 Jul '12

Hi, I have the following question: The documentation describes how to obtain an array view for a small number of dimensions by repeated application of the [] operator of boost::indices. Is there a way to do it in a single call, bypassing the C-type notation? Say, I have a five dimensional multi_array (ma, henceforth) and want to get a slice in one dimension. Is there a call to do this ? I am looking for a generic answer. TIA, Petros PS: was hoping that the ranges_ field of extent_gen could do the trick, since all the info is there - I know it’s in the detail namespace which practically means private/subject-to-change but had no better idea.

1 0

What algorithms for solving the Shortest Paths problem are implemented in BOOST?
by Alex Sadovsky 13 Jul '12

13 Jul '12

I know, Dijkstra's and the Bellman-Ford one are. Is Dial's? http://dl.acm.org/citation.cfm?id=363610 Thanks, Al

2 1

Review Wizard Status Report for July 2012
by Ronald Garcia 13 Jul '12

13 Jul '12

============================================== Review Wizard Status Report for July 2012 ============================================== News ==== 1. Multiprecision Arithmetic Reviewed 2. Boost 1.50.0 Released. New Libraries: 1) Algorithm 2) Functional/OverloadedFunction 3) LocalFunction 4) Utility/IdentityType Open Issues =========== The following libraries have been reviewed and await reports from their review managers: * Conversion - reviewed August 2011; review manager: Gordon Woodhull. * Predef - reviewed February 2012; review manager: Joel Falcou. * Multiprecision - reviewed June 2012; review manager: Jeffrey Hellrung The following libraries have been accepted to Boost, but have not yet been submitted to SVN: * Constrained Value - accepted September 2010; author: Robert Kawulak. * GIL.IO - accepted January 2011; author: Christian Henning. The following libraries have been accepted and submitted to SVN, but have not yet appeared in a release: * Atomic - accepted July 2011; author Helge Bahmann. * Type Traits Introspection - accepted August 2011; author: Edward Diener. * Lockfree - accepted August 2011; author: Tim Blechmann. * Context - accepted January 2012; author: Oliver Kowalke. The following libraries have been accepted provisionally to Boost, but have not been submitted for mini-review and full acceptance: * Endian - accepted provisionally November 2011; author: Beman Dawes. * Log - accepted provisionally March 2010; author: Andrey Semashev. General Announcements ===================== As always, we need experienced review managers. Please take a look at the list of libraries in need of managers and check out their descriptions. In general review managers are active boost participants, including library contributors, infrastructure contributors, and other mailing list participants with a substantial track record of constructive participation. If you can serve as review manager for any of them, email Ron Garcia or John Phillips, "rxg at cs dot cmu dot edu" and "phillips at pacific dot mps dot ohio-state dot edu" respectively. We are also suffering from a lack of reviewers. While we all understand time pressures and the need to complete paying work, the strength of Boost is based on the detailed and informed reviews submitted by you. If you are interested in reviewing a library but won't have time during the review period, you can always prepare your review ahead of time. No rule says you can only work on a review during the review period. A link to this report will be posted to www.boost.org. If you would like us to make any modifications or additions to this report before we do that, please email Ron or John. The review schedule is an unordered list of the libraries awaiting review. As such, any library on the schedule can be reviewed once the developer is ready, a review manager has been secured, and the manager, developer, and wizards agree on a date to schedule the review. Review Schedule =============== * Join (M) * Pimpl (M) * Sorting (M) * Quaternions, Vectors, Matrices (M) * Variadic Macro Data (M) * Block Pointer (M) * Singularity (M) * Extended Complex Numbers (M) * Metaparse (M) * Polygon: Voronoi Extensions * Coroutine * Type Erasure * Range Extensions * Contract * Nowide (M) * ODEint (M) ``(M)`` marks libraries that need review managers. -------------------- Join ---- :Author: Yigong Liu :Review Manager: Needed :Download: http://channel.sourceforge.net/ :Description: Join is an asynchronous, message based C++ concurrency library based on join calculus. It is applicable both to multi-threaded applications and to the orchestration of asynchronous, event-based applications. It follows Comega's design and implementation and builds with Boost facilities. It provides a high level concurrency API with asynchronous methods, synchronous methods, and chords which are "join-patterns" defining the synchronization, asynchrony, and concurrency. Pimpl ----- :Author: Vladimir Batov :Review Manager: Needed :Download: https://github.com/boost-vault/Miscellaneous/blob/master/Pimpl.zip :Description: The Pimpl idiom is a simple yet robust technique to minimize coupling via the separation of interface and implementation and then implementation hiding. This library provides a convenient yet flexible and generic deployment technique for the Pimpl idiom. It's seemingly complete and broadly applicable, yet minimal, simple and pleasant to use. Sorting ------- :Author: Steven Ross :Review Manager: Needed :Download: https://github.com/boost-vault/Sorting :Description: A grouping of 3 templated hybrid radix/comparison-based sorting algorithms that provide superior worst-case and average-case performance to std::sort: integer_sort, which sorts fixed-size data types that support a rightshift (default of >>) and a comparison (default of <) operator. float_sort, which sorts standard floating-point numbers by safely casting them to integers. string_sort, which sorts variable-length data types, and is optimized for 8-bit character strings. All 3 algorithms have O(n(k/s + s)) runtime where k is the number of bits in the data type and s is a constant, and limited memory overhead (in the kB for realistic inputs). In testing, integer_sort varies from 35% faster to 2X as fast as std::sort, depending on processor, compiler optimizations, and data distribution. float_sort is roughly 70% faster than std::sort. string_sort is roughly 2X as fast as std::sort. Quaternions, Vectors, Matrices ------------------------------ :Author: Emil Dotchevski :Review Manager: Needed :Download: http://www.revergestudios.com/boost-qvm/ :Description: QVM defines a set of generic functions and operator overloads for working with quaternions, vectors and matrices of static size. The library also defines vector and matrix data types, however it allows users to introduce their own types by specializing the q_traits, v_traits and m_traits templates. Variadic Macro Data ------------------- :Author: Edward Diener :Review Manager: Needed :Download: `Boost Sandbox <http://svn.boost.org/svn/boost/sandbox/variadic_macro_data/>`__ :Description: This library adds support and functionality for variadic macros to Boost as well as integrating variadic macros with the Boost PP library without changing the latter library in any way. Block Pointer ------------- :Author: Phil Bouchard :Review Manager: Needed :Download: https://svn.boost.org/svn/boost/sandbox/block_ptr/ :Description: Deterministic memory manager of constant complexity capable of handling cyclic collections. Singularity ----------- :Author: Ben Robinson :Review Manager: Needed :Download: https://github.com/cppmaven/Singularity :Description: The Singularity Design Pattern allows you to restrict any class to a single instance. Unlike the infamous Singleton, Singularity gives you direct control over the lifetime of the object, does not require you to grant global access to the object, nor does it limit you to the default constructor for that object. Extended Complex Numbers ------------------------ :Author: Matthieu Schaller :Review Manager: Needed :Download: http://code.google.com/p/cpp-imaginary-numbers/ :Description: The library is an extension of the std::complex class addressing two issues: 1. The standard does not guaranty the behaviour of the complex class if instantiated with types other than float/double/long double. 2. Some calculation where pure imaginary numbers (i.e. multiples of sqrt(-1)) appear are unnecessarily slowed down due to the lack of support for these numbers. The code I submit contains two interleaved classes boost::complex and boost::imaginary which can be instantiated with any type T provided T overloads the usual arithmetic operators and some basic (real) mathematical functions depending on which complex function will be used. It is thus an extended version of Thorsten Ottosen's n1869 proposal (http://www.open-std.org/JTC1/SC22/WG21/docs/papers/2005/n1869.html) Metaparse --------- :Author: Abel Sinkovics :Review Manager: Needed :Download: http://abel.web.elte.hu/metaparse/metaparse.zip :Description: Metaparse is a library for constructing parsers parsing at compile-time based on template metaprogramming. The parsers built with the library take boost::mpl::strings as input and can produce - types - objects (types with public static members) - callable C++ functions (types with public static method) - template metafunction classes as output (based on the input being parsed). On compilers supporting constexpr the library provides the following syntactic sugar for writing the input of the parsers: BOOST_STRING("this is a string") The library can be used for implementing DSLs in C++, including DSLs making C++ template metaprogramming easier (see examples). Polygon: Voronoi Extensions --------------------------- :Author: Andril Sydorchuk :Review Manager: Lucanus Simonson :Download: http://svn.boost.org/svn/boost/sandbox/gtl/ :Description: This library extends Boost.Polygon with the following features: - Robust and efficient implementation of the sweepline algorithm that allows to construct Voronoi diagram, Delaunay triangulation and medial axis of a set of points and line segments. - Coordinates of the output geometries are computed within the 64 machine epsilon relative error (6 mantissa bits). - Voronoi diagram data structure that allows efficient traversal and data association with the output Voronoi graph. - No 3rd party dependencies (e.g. GMP, MPFR), all the required multiple precision types are implemented as part of the library. - The input and output coordinate type domains are configurable via coordinate type traits, thus allowing to compute coordinates of the Voronoi vertices within any required precision. - The full construction of the Voronoi diagram of 100 000 points takes only 0.27 seconds (see benchmarks). Coroutine --------- :Author: Oliver Kowalke :Review Manager: Hartmut Kaiser :Download: http://gitorious.org/boost-dev/boost-dev/archive-tarball/coroutine :Description: This library is an implementation of coroutines and generators using Boost.Context. Type Erasure ------------ :Author: Steven Watanabe :Review Manager: Lorenzo Caminiti :Download: http://sourceforge.net/projects/steven-watanabe.u/files/ :Description: The TypeErasure library is a generalization of boost::any and boost::function. It allows easy composition of arbitrary type erased operators. Range Extensions ---------------- :Author: Akira Takahashi :Review Manager: Neil Groves :Download: https://github.com/faithandbrave/OvenToBoost :Description: This project adds some features of the Oven Range Library to Boost.Range. Features: - Additional Range Adaptors (taken, taken_while, dropped, dropped_while, elements, elements_key, memoized, outdirected) - Extensions for using Lambda (regular function, regular operator) - Infinite Range (iteration function) - and additional range utilities. Contract -------- :Author: Lorenzo Caminiti :Review Manager: Dave Abrahams :Download: http://sourceforge.net/projects/contractpp/files/latest/download :Description: This library implements Contract Programming for the C++ programming language (see the end of this email). In addition, the library implements virtual specifiers (final, override, and new, see C++11), concept checking, and named parameters. This library is implemented for the C++03 standard and it does not require C++11. Nowide ------ :Author: Artyom Beilis :Review Manager: Needed :Download: http://cppcms.com/files/nowide/ :Description: This library makes cross platform Unicode aware programming easier. It provides an implementation of standard C and C++ library functions, such that their inputs are UTF-8 aware on Windows without requiring to use Wide API. ODEint ------ :Author: Karsten Ahnert and Mario Mulansky :Review Manager: Needed :Download: https://github.com/headmyshoulder/odeint-v2 :Description: odeint provides routines for numerically solving Ordinary Differential Equations, a task heavily required when approaching scientific problems numerically. In odeint we have implemented the most common algorithms in a modern, generic way which provides several advantages over existing implementations. The main focus of odeint is to separate algorithms from the underlying basic computation unit. This allows for example to easily use the power of modern GPUs via CUDA or OpenCL to speed up computational heavy simulations. Libraries under development =========================== See http://svn.boost.org/trac/boost/wiki/LibrariesUnderConstruction for a current listing of libraries under development.

1 0

eos_portable_archive for 1.49
by Paul Harris 13 Jul '12

13 Jul '12

Hi all, Does anyone know if eos_portable_archive is still actively used and maintained? It doesn't compile with boost 1.49, and before I try to fix it up, I was wondering if anyone else has fixed it up. cheers Paul

7 11

[1.48] interprocess consumes 100% on 32bit Windows systems
by Bogdan Slusarczyk 13 Jul '12

13 Jul '12

Hi All, I found such problem: N+1 (where N is number of cpu cores) processes with interprocess syncing use 100% cpu on 32 bit Windows system. Cause of bug: https://svn.boost.org/trac/boost/changeset/74110 void sched_yield() -{ Sleep(1); } +{ + if(!SwitchToThread()){ + Sleep(1); + } Test case: #include <windows.h> #include <iostream> int main() { int i = 0; while( true ) { if ( !SwitchToThread() ) { std::cout << "sleep" << i++ << std::endl; Sleep(1); } } } On 32 bit windows system running this in N+1 separate processes will stop printing and use 100% CPU. On 64 bit system for any number of processes printing will not stop. Kind regards, Bogdan

1 0

const native arrays at compile time
by Hicham Mouline 12 Jul '12

12 Jul '12

Hello, I have a number of questions, some of which are boost specific. 1. const std::string cols[] = { "col1", "col2", "col3" }; Is the const native array cols completely a compile-time construct or are std::string objects constructed at runtime? I would guess the latter? 2. const char const* cols[] = { "col1", "col2", "col3" }; This on the other hand would be pure compile time? 3. struct S1 { const char const* cols[] = { "col1", "col2", "col3" }; }; struct S2 { const char const* cols[] = { "colx", "coly", "coly" }; }; template <typename T> /// T is either S1 or S2 struct S { const char const* col1s[] = { "othercol", /// elements of T::cols }; }; Is there a way to build col1s at compile time? MM

3 2

boost any_range
by tolik levchik 12 Jul '12

12 Jul '12

Is it possible the commented below condition. With regular ranges i make as many 'base()' calls as may adaptors i had applied. Obviously it's impossible with any_range. So what should i do ? #include <map> #define BOOST_RANGE_ENABLE_CONCEPT_ASSERT 0 #include <boost/range/adaptors.hpp> #include <boost/range/algorithm.hpp> #include <boost/range/numeric.hpp> #include <boost/bind.hpp> #include <boost/range/any_range.hpp> struct foo{ int x, y; }; inline bool is_valid(int x){ return x > 0;} int main() { using namespace boost::adaptors; using boost::bind; typedef std::map<char, foo> map_t; typedef const int type; typedef boost::any_range< type, boost::forward_traversal_tag, typename boost::add_reference<type>::type, std::ptrdiff_t > forward_range_t; map_t m; forward_range_t rng = m | map_values | transformed(bind(&foo::x, _1)); // note: don't compile without BOOST_RANGE_ENABLE_CONCEPT_ASSERT defined as 0 forward_range_t::const_iterator found = boost::find_if(rng, is_valid); // found == boost::end(m); how to do it right ? }

2 1

serialization with templates
by Unger, Jörg F. 12 Jul '12

12 Jul '12

I'm trying to serialize a template class with multiple template parameters. In the header file, I declare something like template <int T1, int T2> class Node { private: std::array<double,T1> first; std::array<double,T2> second; } BOOST_CLASS_EXPORT_KEY(Node<1,1>) In a separate file, I would use the BOOST_CLASS_EXPORT_IMPLEMENT macro. However, when I'm using the BOOST_CLASS_EXPORT_KEY with a class that has more than one template parameter (as in the example above), I get an error message Error: macro "BOOST_CLASS_EXPORT_KEY" passed 2 arguments, but takes just 1 I'm using gcc 4.7.1 with boost 50 Any ideas, how to solve that problem? Jörg F.

3 2

Is there any interest in getting pseudo random number generation using preprocessor at compile time into the Preprocessor library?
by Alexander Stoyan 12 Jul '12

12 Jul '12

The complete code, approach and efficiency proofs I described in my blog: http://alexander-stoyan.blogspot.com/2012/07/getting-pseudo-random-numbers-a t.html Need your opinion regarding the relevance and the approach correctness of the feature. Thank you in advance.

1 0

[StateChart] Accessing machine and state members from within state constructor
by Andre Puschmann 12 Jul '12

12 Jul '12

Hello, I'd like to outsource some common functionality into a base state which needs to access some member variables from the state machine or from its direct context. I've managed to do exactly this in the constructor of the inherited class but not inside the constructor of the base class. I believe I am missing some bits here. Thanks in advance -Andre Code: #include <boost/statechart/event.hpp> #include <boost/statechart/state_machine.hpp> #include <boost/statechart/state.hpp> #include <boost/statechart/simple_state.hpp> #include <boost/statechart/transition.hpp> #include <boost/statechart/custom_reaction.hpp> #include <iostream> namespace sc = boost::statechart; // event definition struct EvReset : sc::event< EvReset > {}; // forward definition struct Active; // starting state struct State1; // define FSM struct TestFsm : sc::state_machine< TestFsm, Active > { TestFsm() { std::cout << "Start TestFsm.\n"; fsmValue = 0; std::cout << "value: " << fsmValue << std::endl; } ~TestFsm() { std::cout << "Shut down TestFsm.\n"; } public: int fsmValue; }; struct Active : sc::state< Active, TestFsm, State1 > { Active(my_context ctx) : my_base( ctx ) { std::cout << "Start Active state!\n"; outermost_context().fsmValue++; stateValue = 0; std::cout << "value: " << outermost_context().fsmValue << std::endl; } ~Active() { std::cout << "Leave and desctruct Active state!\n"; } public: int stateValue; typedef sc::transition< EvReset, Active > reactions; }; template< class MostDerived, class Context > struct StateBase : sc::state< MostDerived, Context> { typedef sc::state< MostDerived, Context> base_type; typedef typename base_type::my_context my_context; typedef StateBase my_base; StateBase( my_context ctx ) : base_type( ctx ) { std::cout << "StateBase cst" << std::endl; // critical section outermost_context().fsmValue++; // access member of FSM (outermost context) ctx().stateValue++; // access member in direct context } }; struct State1 : StateBase< State1, Active > { State1(my_context ctx) : my_base( ctx ) { std::cout << "State1 cst" << std::endl; outermost_context().fsmValue++; std::cout << "value: " << outermost_context().fsmValue << std::endl; }; ~State1() {}; }; int main() { TestFsm myFSM; myFSM.initiate(); return 0; }

3 4

compilation problem and a couple of boost::variant questions
by Petros 12 Jul '12

12 Jul '12

Hi, I am trying to write some operator that multiplies two variants, each one containing a vector a zero and a unit, where I am trying to use the fact that I know the outcome for multiplying by 0 or by 1. The code (very bare bones) below describes how this is done, by: _ defining dummy structures of Variant-1, 2 _ defining a class that contains the instruction for multiplication _ defining a class (derived from variant) that contains possible outcomes of the multiplication _ defining the operator (only a few of the possible outcomes are shown) Compiling with msvc2010 (intel has similar issues) on win7: First here is the code: #include <boost/variant.hpp> using boost::variant; struct Zero1{ double operator[]( const size_t i ) const { return 0L ; } }; struct One1{ double operator[]( const size_t i ) const { return 1L ; } }; struct Zero2{ double operator[]( const size_t i ) const { return 0L ; } }; struct One2{ double operator[]( const size_t i ) const { return 1L ; } }; struct Vector1{ double operator[]( const size_t i ) const {return double( i ) ; } }; struct Vector2{ double operator[]( const size_t i ) const {return double( 2*i ) ; } }; struct subscript_operator:public boost::static_visitor<double>{ const size_t i_; subscript_operator( const size_t i ):i_(i){} template<typename _v> double operator()( _v const & v ) const { return v[i] ; } }; template <typename _V, typename _Z, typename _U> class VariantT :public variant< _V, _Z, _U > { public: typedef typename _Z zero_type ; typedef typename _U unit_type ; typedef typename VariantT<_V, _Z, _U> self_type ; typedef typename variant< _V, _Z, _U > variant_type ; template < typename _V> explicit VariantT( _V const & v ) :variant_type(v) {} VariantT() {} VariantT( self_type const & v ) :variant_type(static_cast<const variant_type&>(v)) {} template < typename _V> VariantT & operator = ( _V const & v ) { *static_cast<variant_type*>(this) = static_cast<const variant_type&>(v); return(*this); } VariantT & operator = ( self_type const & v ) { *static_cast<variant_type*>(this) = v; return(*this); } double operator[]( const size_t i ) const { boost::apply_visitor( subscript_operator(i) , *this ) ; } bool isZero() const { return which() == 1 ; } bool isUnit() const { return which() == 2 ; } private: }; template < typename _V1, typename _V2 > class MultVarVar{ public: MultVarVar( _V1 const & v1, _V2 const & v2 ) :v1_(v1),v2_(v2) {} ~MultVarVar() {} typedef typename _V1::zero_type zero_type ; typedef typename _V1::unit_type unit_type ; double operator[]( const size_t i ) const { return boost::apply_visitor ( elementwise_visitor( i ), v1, v2 ) ; } private: _V1 const & v1_ ; _V2 const & v2_ ; struct elementwise_visitor : public boost::static_visitor< double > { const size_t & i_; public: elementwise_visitor( const size_t & i ) :i_(i) {} template <typename _V1, typename _V2 > double operator()( _V1 const & v1, _V2 const & v2) const { return v1[i_] * v2[i_] ; } }; }; template < typename _V1, typename _V2 > class MultVarVarResult :public variant<typename MultVarVar<_V1, _V2>, typename MultVarVar<_V1,_V2>::zero_type, typename MultVarVar<_V1,_V2>::unit_type, _V1, _V2 > { public: typedef typename variant< typename MultVarVar<_V1, _V2 > , typename MultVarVar<_V1,_V2>::zero_type, typename MultVarVar<_V1,_V2>::unit_type, _V1, _V2 > variant_type; typedef typename MultVarVarResult<_V1, _V2> self_type ; typedef typename _V1::zero_type zero_type ; typedef typename _V1::unit_type unit_type ; template<typename _V> /*explicit*/ MultVarVarResult( _V const & v ) :variant_type(v) {} MultVarVarResult( self_type const & v ) :variant_type(static_cast<const variant_type&>(v)) {} template < typename _V> MultVarVarResult & operator = ( _V const & v ) { *static_cast<variant_type*>(this) = static_cast<const variant_type&>(v); return(*this); } MultVarVarResult & operator = ( self_type const & v ) { *static_cast<variant_type*>(this) = v; return(*this); } double operator[]( const size_t i ) const { boost::apply_visitor( subscript_operator(i), *this ) ; } private: }; template <typename _V1, typename _V2> MultVarVarResult<_V1, _V2> operator * ( _V1 const & v1, _V2 const & v2 ) { if ( v1.isZero() || v2.isZero() ) return MultVarVarResult<_V1, _V2>( typename MultVarVar<_V1,_V2>::zero_type() ) ; if ( v1.isUnit() ) return MultVarVarResult<_V1, _V2>( v2 ); if ( v2.isUnit() ) return v1 ; else return MultVarVarResult<_V1, _V2>( MultVarVar<_V1, _V2>( v1, v2 ) ) ; } typedef VariantT< Vector1, Zero1, One1 > Variant1; typedef VariantT< Vector2, Zero2, One2 > Variant2; int main(){ Variant1 v1; v1 = Zero1() ; Variant2 v2; v2 = One2() ; auto x = v1 * v2 ; return x[0] == double(0) ; } And here is one of the errors : boost_1_49_0\boost\variant\variant.hpp(1399): error C2666: 'boost::variant<T0_,T1,T2,T3,T4>::convert_construct' : 2 overloads have similar conversions 1> with 1> [ 1> T0_=MultVarVar<Variant1,Variant2>, 1> T1=Zero1, 1> T2=One1, 1> T3=Variant1, 1> T4=Variant2 1> ] 1> c:\_petros\_otc\ext\boost_1_49_0\boost\variant\variant.hpp(1384): could be 'void boost::variant<T0_,T1,T2,T3,T4>::convert_construct<_V,_Z,_U,boost::detail::variant::void_,boost::detail::variant::void_,boost::detail::variant::void_,boost::detail::variant::void_,boost::detail::variant::void_,boost::detail::variant::void_,boost::detail::variant::void_,boost::detail::variant::void_,boost::detail::variant::void_,boost::detail::variant::void_,boost::detail::variant::void_,boost::detail::variant::void_,boost::detail::variant::void_,boost::detail::variant::void_,boost::detail::variant::void_,boost::detail::variant::void_,boost::detail::variant::void_>(const boost::variant<_V,T1,T2> &,long)' 1> with 1> [ 1> T0_=MultVarVar<Variant1,Variant2>, 1> T1=Zero1, 1> T2=One1, 1> T3=Variant1, 1> T4=Variant2, 1> _V=Vector1, 1> _Z=Zero1, 1> _U=One1 1> ] 1> c:\_petros\_otc\ext\boost_1_49_0\boost\variant\variant.hpp(1315): or 'void boost::variant<T0_,T1,T2,T3,T4>::convert_construct<const T>(T &,int,boost::mpl::false_)' 1> with 1> [ 1> T0_=MultVarVar<Variant1,Variant2>, 1> T1=Zero1, 1> T2=One1, 1> T3=Variant1, 1> T4=Variant2, 1> T=Variant1 1> ] 1> while trying to match the argument list '(const Variant1, long)' 1> c:\_petros\_otc\tests\variant\variant\main.cpp(120) : see reference to function template instantiation 'boost::variant<T0_,T1,T2,T3,T4>::variant<_V>(const T &)' being compiled 1> with 1> [ 1> T0_=MultVarVar<Variant1,Variant2>, 1> T1=Zero1, 1> T2=One1, 1> T3=Variant1, 1> T4=Variant2, 1> _V=Variant1, 1> T=Variant1 1> ] 1> c:\_petros\_otc\tests\variant\variant\main.cpp(151) : see reference to function template instantiation 'MultVarVarResult<_V1,_V2>::MultVarVarResult<_V1>(const _V &)' being compiled 1> with 1> [ 1> _V1=Variant1, 1> _V2=Variant2, 1> _V=Variant1 1> ] 1> Any help on this will be greatly appreciated! And the questions: What happens if a variant contains two identical template arguments ? when I create a (variant) object from one of the two identicals, how does it know which template argument I need ? Do I have to write the same code for the specialization of identical _V1 and _V2? Also, am I correct to assume that all this syntax ( element-wise static_visitor’s etc) will be optimized away at a release build ? TVMIA Petros

3 10

Boost 1.49 Locale Conversion failed
by NtVisigoth 12 Jul '12

12 Jul '12

Hello, everyone! I have already answred here: http://lists.boost.org/boost-users/2012/07/75097.php But previous latter badly typed. When using boost::locale with the russian language of the string in UTF-8 encoding I get an error while getting the locale. An exception with the message e.what(): "Conversion failed" is thrown My code is not very different from that in the examples: #define TR(S) boost::locale::translate(S).str() const std::string strDefaultLangId( "en" ); int main( int argc, char * argv[] ) { using namespace std; using namespace boost::locale; int exitCode = EXIT_SUCCESS; try { generator gen; gen.add_messages_path("g:\\source\\boost_locale\\languages\\"); gen.add_messages_domain("messages"); std::string language( argc == 2 ? argv[1] : strDefaultLangId.c_str() ); std::locale loc = gen( language ); locale::global( loc ); std::wstring s = TR(L"hello world"); wcout << s << endl; } catch( exception& e ) { cout << "Error : " << e.what() << endl; exitCode = EXIT_FAILURE; } catch( ... ) { cout << "Unknown error" << endl; exitCode = EXIT_FAILURE; } return exitCode; } The path to the file with the russian language: "g:\source\boost_locale\languages\ru\LC_MESSAGES\messages.mo" What could be wrong? * Is it necessary to use the backends? * Is it yet necessary to call imbue on the stream? But I'd like avoid it because I am going to write the log using glog. Compillers : Microsoft Visual Studio 2008 and 2010 Boost version : 1.49

4 7

Dealing with resistance to Boost
by hano botha 12 Jul '12

12 Jul '12

I am trying to get my organisation to use Boost. I have managed to get it included in source control and we have permission to use it in our unit testing. The main objection to using it in our production code is that it could be a potential security risk. I suggested that we restrict the usage of boost to the template\ headers only libraries. I don't see how the templates in boost can cause more of a security risk than what we have currently with the STL. My question is: How is vulnerabilities in the library dealt with? How is new vulnerabilities communicated to the user's community? I would also like to know historically, how many and how often were vulnerabilities discovered? Any good references would be great. Thanks,

3 2

boost range question
by tolik levchik 12 Jul '12

12 Jul '12

Why min_element give me errors without BOOST_RANGE_ENABLE_CONCEPT_ASSERT defined 0? Is it uses only for make error messages more readable? Is it safe to define it to 0? #include <vector> //#define BOOST_RANGE_ENABLE_CONCEPT_ASSERT 0 #include <boost/range.hpp> #include <boost/range/adaptors.hpp> #include <boost/range/algorithm.hpp> #include <boost/range/numeric.hpp> #include <boost/bind.hpp> struct foo{ int x; }; int main() { using namespace boost::adaptors; using boost::bind; std::vector<foo> vec; auto rng = vec | transformed(bind(&foo::x, _1)); boost::accumulate(rng, 0); // ok boost::min_element(rng); // error }

2 1

Re: [Boost-users] Boost 1.49 msm problems with events
by Kamel Zaarouri, Mr 11 Jul '12

11 Jul '12

Hi, I am having problems with my transition table and events. Let me explain the fake design that illustrates the problem: I have a state machine (myStateMachine) containing 2 states (s0 and s1) and 1 substatemachine (subm1). the substatemachine subm1 contains an initial state 'sub0' and also s1 (the same state as in myStateMachine). this is the main transition table: s0->s1 on event 'ES1' s0->s2 on event 'ES2' s0->subm1 on event 'ESUB' this is the submachine transition table: sub0->s1 on event ES1 now, assume that state s1 is using the event that triggered it to extract some information i.e. struct s1 : public msm::front::state<> { template <class Event,class FSM> void on_entry(Event const& evt,FSM& fsm) { evt.getEventData(); } } so every event that could transition to s1 needs to implement getEventData() method. ->this is normal! now my problem is that ESUB does NOT implement getEventData() but apparently it should. And I don't get why. I am not using ESUB to transition to s1 but I am using ESUB to transition to subm1 and subm1 contains s1 but I don't access it at that point. I hope this is clear. Thank you.

3 2

[asio] asynchronous reading/writing to the tcp stream
by Ovanes Markarian 11 Jul '12

11 Jul '12

Hello *, I go through the ASIO docs, but somehow do not get if I can implement the following scenario: In one thread I would like to send lot's of commands to the server via a tcp connection. In the other thread I would like to start reading the commands being already handled and returned by the server. The commands are parsed by Spirit.QI. My idea was to use a tcp::iostream asynchronously so that I just pass the begin iterator to the output stream to QI and receive parsed data. If there is no output from the server the iterator should block and wait for it. This is a producer-consumer problem, but I would like to solve it with tcp::iostream and without explicit synchronization on my side. Is it possible? If yes, than how? I understand that I can introduce some storage, read bytes to it and notify my hand-crafter iterator, that there is some data that can be read again, but is there a better approach? Thanks, Ovanes

4 6