August 2008 - Boost - lists.boost.org

[filesystem] major problem with 1.36 on OS X
by Matthias Schabel 18 Aug '08

18 Aug '08

Attempting to compile and link the following code with a default build of 1.36 on OS X 10.5.4 (Intel) // test.cpp #include <fstream> #include <iostream> #include <string> #include <vector> //#include <boost/system/error_code.hpp> //#include <boost/system/system_error.hpp> #include <boost/filesystem/operations.hpp> #include <boost/filesystem/path.hpp> int main (int argc, char * const argv[]) { boost::filesystem::create_directory("blah"); return 0; } results in a linker error, even though the method in question is defined inline in <boost/system/error_code.hpp> : Undefined symbols: "boost::system::error_code::message() const", referenced from: boost::system::system_error::what() constin ccyMBSNr.o ld: symbol(s) not found collect2: ld returned 1 exit status This is reproducible both from a clean XCode 3.0 project and from the command line : gcc test.cpp -I/usr/local/include -I .. -L/usr/local/lib - lboost_filesystem-xgcc40-mt -lboost_system-xgcc40-mt -lstdc++ Uncommenting the explicit includes doesn't help, either. This is a weird one... Matthias

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Re: [boost] Boost 1.36.0 release notice
by Beman Dawes 18 Aug '08

18 Aug '08

Joe Gottman wrote: > Beman Dawes wrote: >> Boost 1.36.0 has been released and is available from SourceForge. See >> http://sourceforge.net/projects/boost/ >> >> This release include four new libraries: >> > I just downloaded the version 1.36 and the release history is > completely blank. Grrr... One of my highest priority tasks for the next release is going to be to get a system in place that will automatically scan a release snapshot for the presence of certain files, and optionally verify size, date, and other properties. Thanks for the heads up. --Beman

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Identification library preliminary version
by joel falcou 18 Aug '08

18 Aug '08

Hello all, I've uploaded a preliminary version of my type identification library into the vault (identification-v.01.zip) It's the current implementation of my type debugging facility that provides a simple function and class to build at run-time a human readable string containing the name of its type arguments. Identification supports a simple way to register user-defined types into itself. Samples and documentation are provided. It has been tested on g++ v4+ (both linux and windows) and on MSVC 2008 with equal success. Test on other platform and compiler are welcome as well as general comments on the interface or implementation choices. Thanks in advance.

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[accumulators] combine/parallel_reduce
by Pavol Droba 18 Aug '08

18 Aug '08

Hi, I've just started to use the accumulators library. I must say that I like it a lot. However, I found one feature that I'm missing in the interface. In the time of multicore processors and Thread Building Blocks at hand, it would be nice to be able to use accumulators in parallel computations. To do so, one would need to combine partial computations. In other words, we need accumulator_set::combine(). This would combine the partial computation state from another accumulator_set. This operation would enable the accumulators to be used with parallel_reduce. I'm not expert in statistical computations, but as far as I can see, this should be doable quite easily. Best Regards, Pavol.

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[doc] General Boost documentation suggestion
by Edward Diener 18 Aug '08

18 Aug '08

This is an impassioned plea for all library developers writing documentation about classes and/or functions ( including class templates and function templates ). Please, please put somewhere in the low-level description/explanation of that class and function both the full namespace it is in and the header file which must be included. Numerous times, using the functionality of an otherwise wonderful Boost library, I have had to hunt through the rest of that library's documentation to find the full namespace and header file which must be included in order to correctly use a particular function or class. This is irritatingly time consuming and can be remedied in all cases by the suggestion above. Thank you !

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[shared_ptr][exception] Support for disabled RTTI
by Daniel James 18 Aug '08

18 Aug '08

Using boost with RTTI disabled was recently discussed on the user list, and I had a quick look into it. It seems that shared_ptr added support for the BOOST_NO_TYPEID macro in 1.35: http://svn.boost.org/trac/boost/ticket/1108 But because it now depends on the new exception library, which requires RTTI, it no longer works. Would it be possible to support the macro in Boost.Exception? Daniel

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[shifted_ptr] STL support: 99%
by Phil Bouchard 18 Aug '08

18 Aug '08

Ok, this is awesome. Last week I made changes in the Sandbox I had to revert and rework all over... Now the changes I made in both the pointer and the STL containers are clearly to ones I want to stick with. This brings up interesting concepts at the same time, such as: what should be the right parameter of allocator::deallocate() ? We can't use a raw pointer over there. We can see the non-official patch inside the bits folder and shifted_allocator.hpp which I think solves the problem correctly. Furthermore allocator::allocate() I beleive shouldn't return yet a smart pointer because it creates unnecessary temporaries which can be costly, depending on the smart pointer used. So the typedefs inside shifted_allocator are the way I think they should be understood by the containers... Thanks, -Phil

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"SuperC"
by Phil Bouchard 18 Aug '08

18 Aug '08

Here is a discussion I started with Gordon 2 weeks ago and I wanted to share globally because of its interesting features which aren't related to smart pointers: "I think a huge container inside an application will always suffer from imperfections and this could be a decent alternative to the problem. A map mixed with a list, a vector mixed with a set or all four together offers an infinite set of properties. Let's put it this way. All new "unordered" and multiset containers could easily be implemented as: 1) superc1st<double, list, vector> s1; 2) superc2nd<string, double, map, vector> s2; 3) superc2nd<string, double, map, map> s3; Where (explicit specializations for sake of example and please disregard missing "typename"s): 1) template <> class superc1st<double, list, vector> : public _list<0, void, double>, _vector<1, void, double> {...}; Here are examples of its usage: s1.push_back(5.7); s1[0] = 5.8; 2) template <> class superc2nd<string, double, map, vector> : public _map<0, string, double>::base, _vector<1, string, double>::base {...}; This one can be accessed as such: s2["Height"] = 6.3; // <-- O(log n) s2[10] = 5.9; // <-- O(1) 3) template <> class superc2nd<string, double, map, map> : public _map<0, string, double>::base, _map<1, string, double>::base {...}; To access 3) we could add indexed types we can cast the container to:s3.get<0>()["Age"] = 31; The underscored containers will be defined as: template <int I, typename T, typename U> struct _map : std::map<T, U> { typedef std::map<T, U> base; base & get<I>() { return * this; } // explicit function spec. won't work here (should be Ith type pack cast) }; And: template <int I, typename T, typename U> struct _vector : std::vector<U> { typedef std::vector<U> base; ... }; ... I think this is very easy to implement, cleaner and much more flexible (can use vectors and no container can be forgotten). My brain kernel example already needs something similar extensively..." Thanks, -Phil

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[1.36.0: Graph] unused variable warning in topological_sort.hpp
by Christoph Duelli 18 Aug '08

18 Aug '08

in boost/graph/topological_sort.hpp, line 40 is an unused variable (u): template <typename Edge, typename Graph> void back_edge(const Edge& u, Graph&) { throw not_a_dag(); } Would be great if that could be fixed for the next release. Keep up the great job! Best regards Christoph

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[1.36.0: Serialization] unused variable warning in shared_ptr.hpp
by Christoph Duelli 18 Aug '08

18 Aug '08

in boost/serialization/shared_ptr.hpp, line 133: in the case of NOT "#ifdef BOOST_SERIALIZATION_SHARED_PTR_132_HPP" the variable file_version is not used. Could be fixed by replacing else #endif by else #else (void)file_version; #endif or something similar. Would be great if that could be fixed for the next release. Keep up the great job! Best regards Christoph

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