September 2009 - Boost-users

Problem detecting python
by Philippe Fremy 01 Sep '09

01 Sep '09

Hi, bjam does not seem to pick my python installation on windows. This is running on Windows XP, toolset gcc, boost 1.39, compiling from source with no changes. D:\program\boost_1_39_0>bjam --debug-configuration -d+2 --debug-building [...] notice: [python-cfg] running command '"C:\Python25\python" -c "from sys import *; print 'version=%d.%d\nplatform=%s\nprefix=%s\nexec_prefix=%s\nexecutable=%s' % (version_info[0],version_info[1],platform,prefix,exec_prefix,executable)" 2>&1'notice: [python-cfg] ...does not invoke a working interpreter notice: [python-cfg] No working Python interpreter found. The strange thing is that if I run the same command line, it works perfectly: D:\program\boost_1_39_0>"C:\Python25\python" -c "from sys import *; print 'version=%d.%d\nplatform=%s\nprefix=%s\nexec_prefix=%s\nexecutable=%s' % (version_info[0],version_info[1],platform,prefix,exec_prefix,executable)" 2>&1 version=2.5 platform=win32 prefix=C:\Python25 exec_prefix=C:\Python25 executable=C:\Python25\python.exe Any idea what confuses bjam ? I could not find any log file to see more details of what is going wrong... cheers, Philippe

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Latex
by Dmitry Bufistov 01 Sep '09

01 Sep '09

\renewcommand{\baselinestretch}{0.98}

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[MPL] Front of a set of types
by Marco Guazzone 01 Sep '09

01 Sep '09

Dear all, Consider this: ---[code]--- #include <boost/mpl/front.hpp> #include <boost/mpl/set.hpp> #include <boost/type_traits/is_same.hpp> #define BOOST_TEST_MODULE "boost::mpl::set tests" #define BOOST_TEST_DYN_LINK #define BOOST_TEST_MAIN #include <boost/test/unit_test.hpp> BOOST_AUTO_TEST_CASE( mpl_set ) { typedef boost::mpl::set<int,long,char> s; BOOST_CHECK( (boost::is_same<int, boost::mpl::front<s>::type>::value) ); // Test #1 BOOST_CHECK( (boost::is_same<long, boost::mpl::front<s>::type>::value) ); // Test #2 BOOST_CHECK( (boost::is_same<char, boost::mpl::front<s>::type>::value) ); // Test #3 } ---[/code]--- Reading the docs http://www.boost.org/doc/libs/1_40_0/libs/mpl/doc/refmanual/set.html the "front" of a set<t1,t2,...,tn> return the first element type in s which for me is t1 So what I expect is the test to fail on tests #2 and #3 and hence to succeed on test #1 Instead the test fails on tests #1 and #2 and succeeds on test #3. Looking inside the code I find out this is OK since a setN<T1,..,TN> is defined from TN and set{N-1}<T1,...,T{N-1}>, resulting in TN be the very front element Anyway, in my opinion this is counterintuitive. Maybe a note in the document would be helpful. What do you think? Thank you very much! Cheers, -- Marco

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problem with asio
by pedro chaparro 01 Sep '09

01 Sep '09

hi everyone, i'm new with boost, i've try some examples and they work well but spacifically with programs that use asio libraries i've got some error when i try to compile them, below the line i use to compile, ill apreciate some help thnaks pdro7@ubuntu:~/Desktop$ c++ -I /home/pdro7/Desktop/boost_1_40_0 asio1.cpp -o asio1 /usr/lib/libboost_system-gcc43-mt-1_35.a /usr/lib/libboost_thread-gcc43-mt-1_35.a /usr/lib/libboost_date_time-gcc43-mt-1_35.a /usr/lib/libboost_regex-gcc43-mt-1_35.a /usr/lib/libboost_serialization-gcc43-mt-1_35.a // timer.cpp // ~~~~~~~~~ // // Copyright (c) 2003-2008 Christopher M. Kohlhoff (chris at kohlhoff dot com) // // Distributed under the Boost Software License, Version 1.0. (See accompanying // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) // #include <iostream> #include <boost/asio.hpp> #include <boost/date_time/posix_time/posix_time.hpp> int main() { boost::asio::io_service io; boost::asio::deadline_timer t(io, boost::posix_time::seconds(5)); t.wait(); std::cout << "Hello, world!\n"; return 0; } -- Ing Pedro Alonso Chaparro Valero Ciudad Politecnica de la Innovación iTEAM - Mobile Communications Group Polytechnic University of Valencia C\ Camino de Vera S/N, Edificio 8G 46022 Valencia, Spain

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[Math] Fractional binomial_coefficient
by Ralf M. 01 Sep '09

01 Sep '09

Hi, the binomial coefficients are usually used with integers, but it is also possible to get the binomial coefficient of real values (cf. http://en.wikipedia.org/wiki/Binomial_coefficient ). Maybe this could be added to the boost math library. Here's a sample implementation using standard g++: template <class T> T Choose(T n, T k) { return exp(lgamma(n + 1.0) - lgamma(k + 1.0) - lgamma(n - k + 1.0)); } Examples using double or long double type: C(10.000000, 3.000000) = 120.000000000000 C(10.000000, 3.250000) = 143.236519908866 C(10.000000, 3.500000) = 166.719334273254 C(10.000000, 3.750000) = 189.361086655990 C(10.000000, 4.000000) = 210.000000000000 C(10.500000, 3.000000) = 141.312500000000 C(10.500000, 3.250000) = 171.461136142499 C(10.500000, 3.500000) = 202.979003906250 C(10.500000, 3.750000) = 234.620815915449 C(10.500000, 4.000000) = 264.960937500000

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[BGL] backward warning
by Ralf Goertz 01 Sep '09

01 Sep '09

When compiling with gcc4.3 I get a backward warning from adjacency_list.hpp because it includes hash_set instead of unordered_set (Boost 1.39.0). Will this be fixed soon? Ralf

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