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[config] check for std::numeric_limits<T>::lowest() availability
by vicente.botet 26 Sep '10

26 Sep '10

Hi, I would like to use std::numeric_limits<T>::lowest() when the standard library provides it. As this is a specific function on C++0X, I was looking for a macro on Boost.Config that allows to use it conditionally, unfortunatelly I have not found any. What will be the right way to do that? Any chance <boost/limmits.hpp> manage with that? Best, _____________________ Vicente Juan Botet Escribá http://viboes.blogspot.com/

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[chrono] version 0.6 uploaded
by vicente.botet 26 Sep '10

26 Sep '10

Hi, I have uploaded the version 0.6 of Boost.Chrono which includes New Features: * Added experimental chrono_io from Howard Hinnant. Provides I/O for duration and time_point. Builds on <boost/ratio/ratio_io.hpp> to provide readable and flexible formatting and parsing for types in <boost/chrono.hpp>. The duration unit names can be customized through a new facet: duration_punct. Fixes: * Fix duration values min implementation. Test: * Adapted a lot of tests from libc++/chrono making the lib much more robust. Getting the library. You can get more information from http://svn.boost.org/trac/boost/wiki/LibrariesUnderConstruction#Boost.Chrono Is designed to be generic and useful in a lot of areas of C++ programming, in particular it is absolutely needed to adapt Boost.Thread to the forthcomming C++0x recomendation and the to be review Boost Stopwatches library. The Beman's initial version contained some additional classes to measure and report the elapsed time. These classes are included yet in the package, but have been deprecated. The usefulness of these features has been the motivartion of Boost.Stopwatches, which provide similar facilities in a generic and integrated way. Best regards, _____________________ Vicente Juan Botet Escribá http://viboes.blogspot.com/

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[Boost-users] [BGL] Stoer–Wagner min-cut algorithm
by Daniel Trebbien 26 Sep '10

26 Sep '10

> The usual idiom for that in BGL algorithms is to use an > iterator_property_map on the graph's vertices, built using a vector and > indexed by the vertex_index property map of the graph. You can also use a > shared_array_property_map, which manages its storage internally. If you > are doing a generic algorithm, the logic to manage these maps correctly is > somewhat difficult. One place to look for a template of what to do is the > distance map handling at the bottom of > <boost/graph/dijkstra_shortest_paths.hpp>, particularly > dijkstra_shortest_paths() and detail::dijkstra_dispatch1(). The basic > logic is to look at the named parameter structure that the user passes is > and see if there is an assignment map there. If so, use it; otherwise, > look for a vertex_index map in the named parameter structure, defaulting > to get(vertex_index, g), then use the found vertex_index map to create an > iterator_property_map or shared_array_property_map. Now that compilers > are more compliant, there are probably simpler ways to implement the logic > than to use multiple dispatch functions, but the approach in > dijkstra_shortest_paths.hpp is known to work. > > When you get this algorithm done, you may want to contribute it to BGL to > be added to Boost. We are always interested in new algorithms. > > -- Jeremiah Willcock Hello Jeremiah, I would very much like to contribute my implementation of the Stoer–Wagner min-cut algorithm to BGL. In preparation for this, I have attached a "pre-release" version to this e-mail which has everything needed to build the test case with g++ and GNU Make. Before I add in all of the template code to support "default" template parameters and other niceties, I figured that it would be good to have a review of the code to make sure that I am headed in the right direction. Also, I have tested my code against the example from Stoer & Wagner (1997). It appears to be working correctly, but there might be bugs. I think that it would be good to have more testing. Would someone please review my code? Also, is anyone aware of good examples for testing min-cut implementations? Daniel

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Re: [boost] [B-tree] Continuing development
by Brian Wood 25 Sep '10

25 Sep '10

Beman Dawes: > I'm going to attack variable-length keys/data in several steps. > > 1) Via a very simple string class that has a fixed maximum length, and has a > sizeof() that maximum length + 1. Although this wouldn't be suitable for > really demanding applications, it should be fine for a lot of every day > programming. It is totally non-invasive, so is available right now. See > http://github.com/Beman/Boost-Btree/blob/master/boost/btree/detail/fixstr.h…, > or use your own if you've already got such an animal. Just fyi, I've been experimenting with a similar string -- http://webEbenezer.net/misc/lil_string.hh . If an operation would result in a string with length more than 255, an exception is thrown. This allows the length of the string to be marshalled with one byte. As you mention this limitation is not a problem in many circumstances. I'd quibble a little with it not being suitable for demanding applications. I think it is fine to use it in that context, but that you might need to also use other string classes. -- Brian Wood Ebenezer Enterprises http://webEbenezer.net (651) 251-9384

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[B-tree] Continuing development
by Beman Dawes 24 Sep '10

24 Sep '10

There was enough positive response to the "Interest in B-tree library for Boost?" thread that I plan to continue development. * The immediate action items for the next few weeks are to get the library working with more compilers, to move the timer and endian stuff to detail, and to begin testing on Linux and other Unix-like platforms. Also try to extend the test cases to uncover more bugs. * Variable length keys and data, particularly strings, are a very high priority. * Development will be hosted at http://github.com/Beman/Boost-Btree - I'm liking Git quite a lot and using it is the best way for me to learn more. For those who want to follow along, the git equivalent to an svn checkout is: mkdir btree cd btree git clone git://github.com/Beman/Boost-Btree.git . and the git equivalent to svn update is: cd btree git pull * Please give the library a try. I need feedback based on actual use. Thanks, --Beman

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[conversion] version 0.5.0 available
by vicente.botet 24 Sep '10

24 Sep '10

Hi, I have uploaded the version 0.5 of Boost.Conversion which includes respect ot the preceding version New Features: * Added a pack funcrion able to pack the Source and the Target constructor arguments in one parameter used (to convert vectors). * Added conversion between std::vector of explicitly convertible types. Fixes: * Port to more recent compilers * Warning removal You can get more information from http://svn.boost.org/trac/boost/wiki/LibrariesUnderConstruction#Boost.Conve…. Best, _____________________ Vicente Juan Botet Escribá http://viboes.blogspot.com/

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[type_traits] conditional transformation
by vicente.botet 24 Sep '10

24 Sep '10

Hi, In 20.7.6.6 Other transformations [meta.trans.other] C++0x introduce a conditional template that is equicalent to mpl::if_c template <bool B, class T, class F> struct conditional; If B is true, the member typedef type shall equal T. If B is false, the member typedef type shall equal F. Could this be added to the Boost.TypeTraits? Thanks, _____________________ Vicente Juan Botet Escribá http://viboes.blogspot.com/

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Fwd: [test] inconsistent dll linkage warnings and BOOST_TEST_DECL and unit_test_main.ipp
by Felipe Magno de Almeida 24 Sep '10

24 Sep '10

Hello, Since I didn't receive any replies in boost-users list, I'm forwarding here. ---------- Forwarded message ---------- From: Felipe Magno de Almeida <felipe.m.almeida(a)gmail.com> Date: Wed, Sep 22, 2010 at 1:03 PM Subject: [test] inconsistent dll linkage warnings and BOOST_TEST_DECL and unit_test_main.ipp To: boost-users(a)lists.boost.org Hi, When I compile /boost//unit_test_framework as a dependency in a boost.build project I get errors with BOOST_TEST_DECL with some definitions in .ipp files. It seems BOOST_TEST_DECL is suppose to be used in functions that aren't defined for the user and that must be exported/imported depending if included by test's source or the user's source files. But .ipp files use BOOST_TEST_DECL which are included by the user with msvc-8.0 compiler and then it gives errors about that __declspec(dllimport) doesn't allow definition. To fix it I just changed BOOST_TEST_DECL for BOOST_TEST_CALL_DECL in the .ipp files. It works correctly with gcc in linux though. Regards, -- Felipe Magno de Almeida

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aligned_storage in unions
by dherring＠ll.mit.edu 24 Sep '10

24 Sep '10

Hi, While C++0x promises to change things (see draft spec section 9.5), C++ currently does not allow unions to contain members having a nontrivial constructor, operator=, or destructor. This excludes std::string, std::complex, structures containing either, etc. The "standard" workaround is to allocate your own memory and use manual type casting. Boost::aligned_storage can be used to maintain proper alignment, but it cannot be placed inside a union due to the default ctor, dtor, and noncopyable functions. Thus I am forced to use part of boost::detail. Here is a simple example. #include <boost/type_traits/aligned_storage.hpp> // define a union-safe wrapper template <class T> struct UnWrap { boost::detail::aligned_storage::aligned_storage_imp< sizeof(T), boost::alignment_of<T>::value> space; T * get() const { return static_cast<T *>(space.address()); } T * operator->() const { return get(); } T & operator*() const { return *get(); } }; union U { UnWrap<std::string> s; int x; }; U u; new (u.s.get()) std::string; *u.s="hi"; Questions: - Is there a better way to do this? - Am I doing something blatantly wrong? - Could aligned_storage_impl be exposed for such uses? (AIUI, the detail namespace contains unsupported internals.) Thanks, Daniel

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[ratio] 0.2 Review version uploaded
by vicente.botet 24 Sep '10

24 Sep '10

Hi, I have uploaded the version of the Boost Ratio library to be review. What is Boost.Ratio? =============== Boost.Ratio is a portable implementation of the C++0x Standard Library's compile-time rational arithmetic working on C++03 and C++0x compilers. Boost.Ratio provides: * A class template, ratio, for specifying compile time rational constants such as 1/3 of a nanosecond or the number of inches per meter. ratio represents a compile time ratio of compile time constants with support for compile time arithmetic with overflow and division by zero protection * A textual representation of boost::ratio<N, D> in the form of a std::basic_string. Other types such as boost::duration will use these strings to aid in their I/O. This library is header-only and is designed to be generic and useful in a lot of areas of C++ programming, in particular it is absolutely needed to Boost.Chrono and Boost.Stopwatches. Boost.Units contain a similar class: static_rational. You can get more complete information from http://svn.boost.org/trac/boost/wiki/LibrariesUnderConstruction#Boost.Ratio Best regards, _____________________ Vicente Juan Botet Escribá http://viboes.blogspot.com/

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