Hello, David. Wednesday, November 12, 2008 at 8:14:55 PM you wrote: DA> on Wed Nov 12 2008, Sergey Sadovnikov <flex_ferrum-AT-artberg.ru> wrote:
By the way when C++0x will be committed and std::tr1 namespace will be merged with std namespace a lot of code will become uncompilable because of both std and boost namespaces exposed into global or local scope.
DA> "Doctor, it hurts when I do this..." :) DA> Sorry to be glib, but I really can't get too worked up over this. DA> This is why we have namespaces. If you erase the namespace boundaries, DA> collisions happen. Should anyone be surprised that names in Boost, a DA> library collection specifically aimed at standardization, eventually DA> match some of those in std::? Absolutely right, but... Let's see an example. Just get the one of the boost test cases (http://www.boost.org/doc/libs/1_37_0/libs/function/test/lambda_test.cpp) and try to compile with gcc 4.3.2: ----------------------------------------------------------------------- // Boost.Function library // Copyright Douglas Gregor 2002-2003. Use, modification and // distribution is subject to 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) // For more information, see http://www.boost.org #include <iostream> #include <cstdlib> #include <boost/test/minimal.hpp> #include <boost/lambda/lambda.hpp> #include <boost/lambda/bind.hpp> #include <boost/function.hpp> using namespace std; using namespace boost; using namespace boost::lambda; static unsigned func_impl(int arg1, bool arg2, double arg3) { return abs (static_cast<int>((arg2 ? arg1 : 2 * arg1) * arg3)); } int test_main(int, char*[]) { function <unsigned(bool, double)> f1 = bind(func_impl, 15, _1, _2); function <unsigned(double)> f2 = bind(f1, false, _1); function <unsigned()> f3 = bind(f2, 4.0); f3(); return 0; } ----------------------------------------------------------------------- Compiler says: P:\projects\Tests\Sandbox\C++0x\gcc43>g++ -std=c++0x -IP:\projects\common\boost_1.36.0 boost_test1.cpp boost_test1.cpp: In function 'int test_main(int, char**)': boost_test1.cpp:30: error: reference to 'function' is ambiguous P:\projects\common\boost_1.36.0/boost/function/function_base.hpp:99: error: candidates are: template<class Signature> struct boost::function s:\programming\mingw\bin\../lib/gcc/mingw32/4.3.2/include/c++/tr1_impl/functional:1464: error: template<class _Signature> struct std::function boost_test1.cpp:30: error: functional cast expression list treated as compound expression boost_test1.cpp:30: error: expected primary-expression before 'unsigned' boost_test1.cpp:30: error: expected `;' before 'unsigned' boost_test1.cpp:31: error: reference to 'function' is ambiguous P:\projects\common\boost_1.36.0/boost/function/function_base.hpp:99: error: candidates are: template<class Signature> struct boost::function s:\programming\mingw\bin\../lib/gcc/mingw32/4.3.2/include/c++/tr1_impl/functional:1464: error: template<class _Signature> struct std::function boost_test1.cpp:31: error: expected primary-expression before 'unsigned' boost_test1.cpp:31: error: expected `;' before 'unsigned' boost_test1.cpp:32: error: reference to 'function' is ambiguous P:\projects\common\boost_1.36.0/boost/function/function_base.hpp:99: error: candidates are: template<class Signature> struct boost::function s:\programming\mingw\bin\../lib/gcc/mingw32/4.3.2/include/c++/tr1_impl/functional:1464: error: template<class _Signature> struct std::function boost_test1.cpp:32: error: 'f3' was not declared in this scope boost_test1.cpp:32: error: 'f2' was not declared in this scope As you can see <tr1/functional> header isn't explicitly included but compilation was failed. I mean that code which is conform to the some boost examples or other *same* guidelines which explicitly or implicitly expose both 'boost' and 'std' namespaces into global or local scope could become automatically uncompilable... -- Best Regards, Sergey mailto:flex_ferrum@artberg.ru