January 2009 - Boost - lists.preview.boost.org

MSVC9 SFINAE quirks?
by Simonson, Lucanus J 14 Jan '09

14 Jan '09

Is there some gotcha about metaprogramming with MSVC9? I recently finished my geometry library rewrite and found that I couldn't port it to windows because the SFINAE overloading of generic functions is viewed as ambiguous in the more complex cases, but was readily accepted by gcc and icc in linux. The following code compiles in recent versions of gcc, but fails in MSVC9 //simple SFINAE overload of foo works in both template <typename T> typename gtl_if<typename is_mutable_polygon_90_type<T>::type>::type foo(const T& t) { return gtl_yes(); } template <typename T> typename gtl_if<typename is_mutable_polygon_45_type<T>::type>::type foo(const T& t) { return gtl_yes(); } //metafunction wrapper around SFINAE to supply return type works in both template <typename T> typename requires_1<typename gtl_if<typename is_mutable_polygon_90_type<T>::type>::type, void>::type foo2(const T& t) { } template <typename T> typename requires_1<typename gtl_if<typename is_mutable_polygon_45_type<T>::type>::type, void>::type foo2(const T& t) { } //meta function wrapper around two checks works in gcc but not msvc9 // error C2668: 'gtl::foo4' : ambiguous call to overloaded function template <typename polygon_type, typename polygon_type_2> typename requires_1< typename gtl_if< typename gtl_and< typename is_mutable_polygon_90_type<polygon_type>::type, typename is_mutable_polygon_90_type<polygon_type_2>::type >::type>::type, polygon_type>::type foo4(polygon_type& polygon, const polygon_type_2& point) {return point;} template <typename polygon_type, typename polygon_type_2> typename requires_1< typename gtl_if< typename gtl_and< typename is_mutable_polygon_45_type<polygon_type>::type, typename is_mutable_polygon_45_type<polygon_type_2>::type >::type>::type, polygon_type>::type foo4(polygon_type& polygon, const polygon_type_2& point) {return point;} int main() { using namespace gtl; polygon_45_data<int> p45; foo(p45); foo2(p45); foo4(p45, p45); //error here //this works as expected and has no syntax error in msvc9 gtl_if<gtl_and< is_mutable_polygon_45_type<polygon_45_data<int> >::type, is_mutable_polygon_45_type<polygon_45_data<int> >::type >::type>::type a; //this works as expected, generating syntax error in msvc9 // error C2039: 'type' : is not a member of 'gtl::gtl_if<gtl::gtl_no> gtl_if<gtl_and< is_mutable_polygon_90_type<polygon_45_data<int> >::type, is_mutable_polygon_90_type<polygon_45_data<int> >::type >::type>::type b; Does someone like Steve Wanatabe with more experience with MS compilers know what I have inadvertently run afoul of and how to get myself out of this jam? Thanks, Luke

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[mp_int] Incorrect comparison with native types
by Nathan Kitchen 13 Jan '09

13 Jan '09

When I create an negative mp_int outside the range of a native type and compare it to a number of that type, I get incorrect results. Here is an example to reproduce the behavior: #include <iostream> #include <limits> #include <boost/cstdint.hpp> #include <boost/mp_math/mp_int.hpp> using namespace boost::mp_math; using namespace std; int main() { int32_t MIN = numeric_limits<int32_t>::min(); mp_int<> a = MIN; cout << a << endl; a -= 1; // Should print "-2147483649 1" but prints "-2147483649 0" instead cout << a << ' ' << (a < MIN) << endl; return 0; }

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1.38 release schedule
by John Maddock 13 Jan '09

13 Jan '09

Since there haven't been any announcements, do I correctly assume that the 1.38 schedule is likely to slip by a couple of weeks? Cheers, John.

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Pondering Futures
by Tom Brinkman 13 Jan '09

13 Jan '09

Ponderings on the Futures Library: What is the status of Anthony Williams' submission of the futures library to the c++ standards committee? Is it more prudent to wait to find out what the c++ standards committe is going to do first, before adding a possibly incompatible version of the futures library to boost? One could ask, if Anthony's submission is approved by the c++ standards committe, what is the point of adding a "futures" library to boost as well? Is a seperate library needed? What is the advantage of having a root level library called boost::futures? Why would it not be perferable to just extend boost::thread with the additional capabiltity to handle "futures"? Futures are a very useful concept, and I have used them personally. The c++ commitee is correctly considering adding them to the standard. I would be interested in hearing the authors views on their "grand" vision for parallel programming in general and how their "futures" library submissions fit into this vision. tom brinkman

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[fusion] mpl::is_sequence<fusion::vector<> >::type::value should work right?
by Dean Michael Berris 13 Jan '09

13 Jan '09

Hi Guys, I've tried the following minimal test with the latest in trunk and I get an error with GCC 4.2. #include <boost/fusion/container/vector.hpp> #include <boost/static_assert.hpp> int main(int argc, char *argv[]) { BOOST_STATIC_ASSERT((boost::mpl::is_sequence<boost::fusion::vector<> >::type::value)); return EXIT_SUCCESS; } The error is pasted below: /home/dean/boost_trunk/boost/mpl/begin_end.hpp: In instantiation of 'boost::mpl::begin<boost::fusion::vector<boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_> >': /home/dean/boost_trunk/boost/mpl/is_sequence.hpp:95: instantiated from 'boost::mpl::is_sequence<boost::fusion::vector<boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_> >' fusion_is_sequence_test.cpp:5: instantiated from here /home/dean/boost_trunk/boost/mpl/begin_end.hpp:35: error: invalid use of incomplete type 'struct boost::mpl::begin_impl<boost::fusion::fusion_sequence_tag>' /home/dean/boost_trunk/boost/mpl/begin_end_fwd.hpp:19: error: declaration of 'struct boost::mpl::begin_impl<boost::fusion::fusion_sequence_tag>' fusion_is_sequence_test.cpp: In function 'int main(int, char**)': fusion_is_sequence_test.cpp:5: error: 'type' is not a member of 'boost::mpl::is_sequence<boost::fusion::vector<boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_> >' fusion_is_sequence_test.cpp:5: error: template argument 1 is invalid fusion_is_sequence_test.cpp:5: error: template argument 1 is invalid Is this a bug? HTH -- Dean Michael C. Berris Software Engineer, Friendster, Inc.

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[Signals] Early exit on call
by Kisso Bajslovski 12 Jan '09

12 Jan '09

Hi, I wonder if there's any way to end a call early. For example, if we have 4 connections to a signal, and when the first 2nd is called it wants to abort and avoid the calls to the last 2 connections.

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[PhD] todo: use sum() consistently all places ... make it easy to switch to kahanSum() or to optomize
by Thorsten Ottosen 12 Jan '09

12 Jan '09

-Thorsten

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[Review] UUID review results
by Hartmut Kaiser 12 Jan '09

12 Jan '09

Hi all, Some while ago we have had a lively discussion during the review of Andy Thompkin's UUID library. I counted 11 votes, 10 'yes' votes and one 'no' vote. IMHO the 'no' vote has been superseded by the followup discussion and all issues have been resolved. Almost all reviewers stated the UUID library to be very useful. Given the overwhelming number of 'yes' votes the UUID library is accepted for inclusion into Boost. Before inclusion into the Boost SVN Andy will need to fix a couple of minor issues as discussed during the review, some of which are: - POD-ness - lexical_cast - default construction Congratulations to Andy for his effort related to pushing the UUID library forward. I hope to see active development and maintenance of this library in the future. Regards Hartmut Review Manager

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[iostreams]howto replace ostream buffer?
by Larry Evans 11 Jan '09

11 Jan '09

How can one use iostreams::filtering_streambuf to replace the std::basic_streambuf used by cout. I've tried the code in 1st attachment; however, that code produces the output in 2nd attachment. The desired output is shown in 3ird attachment. How should the code be modified to get the desired output? TIA. -regards, Larry Hello World! is_complete=1 3ird Hello! Hello World! is_complete=1 2ND HELLO! 3ird Hello!

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Proposal: Add Loki Library's SafeFormat to Boost:
by Tom Browder 11 Jan '09

11 Jan '09

The last Loki thread I see here is the one from 2002 discussing adding Loki to Boost. I asked Andrei once about doing that specifically for the Loki SafeFormat functions (FPrint, Printf, and SPrintf) and he said FPrintf wasn't good enough yet. However, I find all of them very useful and would love to see them added to the Boost library I know Boost has Format now, but SafeFormat has some advantages over Boost.Format, one of which is that FPrintf can be output to C++ streams as well as to FILE pointers--very handy when one is gradually converting legacy code to using C++ streams. In addition, I find the SafeFormat family much easier to use than Boost.Format. Andrei's original comments regarding FPrintf's shortcomings are here: https://sourceforge.net/forum/message.php?msg_id=4525195 His "Dr. Dobb's Journal" article describing SafeFormat is here: http://www.ddj.com/cpp/184401987 Thank you for your consideration. Warmest regards, -Tom Tom Browder Niceville, Florida USA

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