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

[BGL]Standard Breadth First Visitor
by Moritz Beber 07 Jan '09

07 Jan '09

Hello everyone, I can't seem to wrap my head around implementing a BFS Visitor and color map required by the breadth_first_visitor function. I want to use it to find connected parts of a graph and after the algorithm has run I plan to clear all white nodes. If anyone could provide me with a code example or link to one implementing really only default behaviour I'd appreciate it immensely. Have a happy new year, Moritz

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[fusion] const and transform algorithm
by vicente.botet 07 Jan '09

07 Jan '09

Hi, What is the reason fusion::transform taskes a const Sequence? template< typename Sequence, typename F > typename result_of::transform<Sequence const, F>::type transform( Sequence const& seq, F f); Does this means that the transform do not change the sequence itself o also its elements? Why the following do not compiles struct get { template<typename Sig> struct result; template<typename T> struct result<get(T)> { typedef typename boost::remove_reference<T>::type ACT; typedef typename ACT::result_type type; }; template<typename ACT> typename ACT::result_type operator()(ACT& act) const { return act.get(); } }; boost::tuple<shared_future<int>,shared_future<char> > t; boost::fusion::result_of::transform< boost::tuple<shared_future<int>,shared_future<char> > , get>::type res= boost::fusion::transform(t, get()); transform call to get()(const shared_future<int>&act). How can I make a transformation changing also the sequence itself? The result of transform is a transform_view, so the function get is not really called. How can I assign this to a boost::tuple<int, char> = ??(boost::fusion::transform(t, get())); boost::as_vector? Is there a as_tuple function? Should this force the evaluation of the get function? Thanks, Vicente

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Updating my local boost.
by Robert Jones 06 Jan '09

06 Jan '09

I guess this question is more appropriate to the Subversion maillist, but I'm not subscribed to that, so it might take upto 24 hours to appear there. I'm hoping someone here will know the answer! My organisation maintains its boost libraries under its own Subversion repository. This strikes me as a bit odd, but no reason really why not AFAICS. However, the version in our repository is 1.33.1, and I'd like to upgrade to latest 1.36 release. Our network prevents me accessing the Boost subversion repository, so I have to download the tarball and unpack. Then what do I do? I basically want to overwrite our existing boost code with the newer code, but maintain our local edit history so we can see what's changed locally between our old boost code and new. Hence there are lots of additions, changes and deletions, all of which I want to be able see (that's see the differences between our old code and new code, not all the individual boost commits). How can I do this? Thanks - Rob.

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[bind][function] Newbie finds errors, but in Boost or between chair and keyboard?
by Jeroen N. Witmond 06 Jan '09

06 Jan '09

Greetings, I'm a newbie, at least to Boost, and I have been playing around with it to get familiar with it, and to improve my c++ skills. :) I've run into two problems with boost::bind (and I suspect there is a connection with boost::function). The two programs at the bottom of this message demonstrate these problems. Can anybody shed a light on this? Are these errors in Boost, or did I miss something in the documentation? Should I ask on another mailing list? Or should I file a bug report? Platform: linux-x86 Compiler: GNU C++ version 4.1.2 20061115 (prerelease) (Debian 4.1.1-21) STL : GNU libstdc++ version 20061115 Boost : 1.35.0 Regards, Jeroen. ------------------------------------------------------------------------ #include <boost/bind.hpp> #include <boost/function.hpp> bool doit(int i) { return i > 0; } int main(void) { boost::function1<bool, int> mything; mything = boost::bind(doit, 3); // The statement below results in error: // bind-and-function.cpp:24: error: no match for call to // $-1òø(boost::function1<bool, int, // std::allocator<boost::function_base> >) ()$-1òù // /usr/include/boost/function/function_template.hpp:819: note: // candidates are: typename boost::function1<R, T0, // Allocator>::result_type boost::function1<R, T0, // Allocator>::operator()(T0) const [with R = bool, T0 = int, // Allocator = std::allocator<boost::function_base>] return mything() ? 0 : 1; } ------------------------------------------------------------------------ #include <boost/bind.hpp> #include <boost/function.hpp> #include <cassert> struct anything { void operator()(int var1, int var2, boost::function1<void, int>& mything) { assert(var1 == 12345); assert(var2 == 67890); mything(var1 + var2); } void one_arg(int var3, int var4) { assert(var3 == var4); } } something; int main(void) { // Building and running an expression in small steps works. boost::function1<void, int> one_arg_f = boost::bind(&anything::one_arg, &something, _1, 80235); boost::function2<void, int, int> parentheses_f = boost::bind(&anything::operator(), &something, _1, _2, one_arg_f); parentheses_f(12345, 67890); // This also works. boost::bind(&anything::operator(), &something, _1, _2, one_arg_f)(12345, 67890); // Change either zero in the preprocessor consitionals to one to // demonstrate the problem. In my setup, changing both zeroes to // ones results only in an error message for the first statement. // Leaving both zeroes in place makes this code compile and run to an // exit code of zero. #if 0 // But replacing one_arg_f by its value fails to compile: // /usr/include/boost/bind.hpp:413: error: invalid use of void // expression boost::bind(&anything::operator(), &something, _1, _2, boost::bind(&anything::one_arg, &something, _1, 80235)) (12345, 67890); #elif 0 // Separating construction and execution does not help, but shows it // is the construction that is failing. boost::function2<void, int, int> parentheses_f2 = boost::bind(&anything::operator(), &something, _1, _2, boost::bind(&anything::one_arg, &something, _1, 80235)); parentheses_f2(12345, 67890); #endif // Replacing the second _1 by _3 results in even weirder error messages. return 0; } ------------------------------------------------------------------------

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[Units] root_typeof_helper documentation
by David Walthall 06 Jan '09

06 Jan '09

Hello. I ran across a slight documentation issue when using Boost.Units root_typeof_helper. http://www.boost.org/doc/libs/1_37_0/doc/html/boost/units/root_typeof_helpe… and operators.hpp The issue is that BaseType is not defined. (Was that code copied from power_typeof_helper?) In addition, for both power_typeof_helper and root_typeof_helper, it would be useful to mention that Exponent and Index are of type boost::units::static_rational<N,D>. Thanks for the great library! David

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[Units] Bug with BOOST_UNITS_STATIC_CONSTANT and precompiled headers on MSVC
by David Walthall 06 Jan '09

06 Jan '09

I think that I've run across a bug, either in Units, or in MSVC. Because it only appears when precompiled headers are in use, I suspect it may be a bug in MSVC. Basically, if BOOST_UNITS_STATIC_CONSTANT is used in a header that is compiled into the precomiled header, there will be linker errors. Here is my information: Microsoft Windows XP Professional x64 Edition Microsoft Development Environment 2003 Version 7.1.6030 Microsoft Visual Studio .NET 2003 Service Pack 1 (KB918007) Below is the minimial code to reproduce the error. There are 4 files, stdafx.h, stdafx.cpp (which is used to create the pch), a.cpp, and b.cpp. The same code without precompiled headers turned on links fine. // start of stdafx.cpp #include "stdafx.h" // end of stdafx.cpp // start of stdafx.h #ifndef STDAFX_H_328A91DC_3924_466E_80EA_C9BB6CBF7638 #define STDAFX_H_328A91DC_3924_466E_80EA_C9BB6CBF7638 #include <boost/units/systems/si/length.hpp> BOOST_UNITS_STATIC_CONSTANT(ONE_METER, boost::units::si::length); #endif // end of stdafx.h // start of a.cpp #include "stdafx.h" int main(void) { boost::units::si::meter; return 0; } // end of a.cpp // start of b.cpp #include "stdafx.h" int main2(void) { boost::units::si::meter; return 0; } // end of b.cpp Here is the error message: unit.obj : error LNK2005: "class unit<struct boost::units::list<struct boost::units::dim<struct boost::units::length_base_dimension,class boost::units::static_rational<1,1> >,struct boost::units::dimensionless_type>,struct boost::units::homogeneous_system<struct boost::units::list<struct boost::units::si::meter_base_unit,struct boost::units::list<struct boost::units::scaled_base_unit<struct boost::units::cgs::gram_base_unit,struct boost::units::scale<10,class boost::units::static_rational<3,1> > >,struct boost::units::list<struct boost::units::si::second_base_unit,struct boost::units::list<struct boost::units::si::ampere_base_unit,struct boost::units::list<struct boost::units::si::kelvin_base_unit,struct boost::units::list<struct boost::units::si::mole_base_unit,struct boost::units::list<struct boost::units::si::candela_base_unit,struct boost::units::list<struct boost::units::angle::radian_base_unit,struct boost::units::list<struct boost::units::angle::steradian_base_unit,struct boost::units::dimensionless_type> > > > > > > > > >,void>::boost::unit<struct boost::units::list<struct boost::units::dim<struct boost::units::length_base_dimension,class boost::units::static_rational<1,1> >,struct boost::units::dimensionless_type>,struct boost::units::homogeneous_system<struct boost::units::list<struct boost::units::si::meter_base_unit,struct boost::units::list<struct boost::units::scaled_base_unit<struct boost::units::cgs::gram_base_unit,struct boost::units::scale<10,class boost::units::static_rational<3,1> > >,struct boost::units::list<struct boost::units::si::second_base_unit,struct boost::units::list<struct boost::units::si::ampere_base_unit,struct boost::units::list<struct boost::units::si::kelvin_base_unit,struct boost::units::list<struct boost::units::si::mole_base_unit,struct boost::units::list<struct boost::units::si::candela_base_unit,struct boost::units::list<struct boost::units::angle::radian_base_unit,struct boost::units::list<struct boost::units::angle::steradian_base_unit,struct boost::units::dimensionless type> > > > > > > > > >,void> const & const boost::units::si::`anonymous namespace'::meter" (?meter@?A0x490e06d9@si@units@boost@@3ABV?$unit@U?$list@U?$dim@Ulength_base_dimension@units@boost@@V?$static_rational@$00$00@23@@units@boost@@Udimensionless_type@23@@units@boost@@U?$homogeneous_system@U?$list@Umeter_base_unit@si@units@boost@@U?$list@U?$scaled_base_unit@Ugram_base_unit@cgs@units@boost@@U?$scale@$09V?$static_rational@$02$00@units@boost@@@34@@units@boost@@U?$list@Usecond_base_unit@si@units@boost@@U?$list@Uampere_base_unit@si@units@boost@@U?$list@Ukelvin_base_unit@si@units@boost@@U?$list@Umole_base_unit@si@units@boost@@U?$list@Ucandela_base_unit@si@units@boost@@U?$list@Uradian_base_unit@angle@units@boost@@U?$list@Usteradian_base_unit@angle@units@boost@@Udimensionless_type@34@@34@@34@@34@@34@@34@@34@@23@@34@@units@boost@@@23@X@34@B) already defined in stdafx.obj unit2.obj : error LNK2005: "class unit<struct boost::units::list<struct boost::units::dim<struct boost::units::length_base_dimension,class boost::units::static_rational<1,1> >,struct boost::units::dimensionless_type>,struct boost::units::homogeneous_system<struct boost::units::list<struct boost::units::si::meter_base_unit,struct boost::units::list<struct boost::units::scaled_base_unit<struct boost::units::cgs::gram_base_unit,struct boost::units::scale<10,class boost::units::static_rational<3,1> > >,struct boost::units::list<struct boost::units::si::second_base_unit,struct boost::units::list<struct boost::units::si::ampere_base_unit,struct boost::units::list<struct boost::units::si::kelvin_base_unit,struct boost::units::list<struct boost::units::si::mole_base_unit,struct boost::units::list<struct boost::units::si::candela_base_unit,struct boost::units::list<struct boost::units::angle::radian_base_unit,struct boost::units::list<struct boost::units::angle::steradian_base_unit,struct boost::units::dimensionless_type> > > > > > > > > >,void>::boost::unit<struct boost::units::list<struct boost::units::dim<struct boost::units::length_base_dimension,class boost::units::static_rational<1,1> >,struct boost::units::dimensionless_type>,struct boost::units::homogeneous_system<struct boost::units::list<struct boost::units::si::meter_base_unit,struct boost::units::list<struct boost::units::scaled_base_unit<struct boost::units::cgs::gram_base_unit,struct boost::units::scale<10,class boost::units::static_rational<3,1> > >,struct boost::units::list<struct boost::units::si::second_base_unit,struct boost::units::list<struct boost::units::si::ampere_base_unit,struct boost::units::list<struct boost::units::si::kelvin_base_unit,struct boost::units::list<struct boost::units::si::mole_base_unit,struct boost::units::list<struct boost::units::si::candela_base_unit,struct boost::units::list<struct boost::units::angle::radian_base_unit,struct boost::units::list<struct boost::units::angle::steradian_base_unit,struct boost::units::dimensionles s_type> > > > > > > > > >,void> const & const boost::units::si::`anonymous namespace'::meter" (?meter@?A0x490e06d9@si@units@boost@@3ABV?$unit@U?$list@U?$dim@Ulength_base_dimension@units@boost@@V?$static_rational@$00$00@23@@units@boost@@Udimensionless_type@23@@units@boost@@U?$homogeneous_system@U?$list@Umeter_base_unit@si@units@boost@@U?$list@U?$scaled_base_unit@Ugram_base_unit@cgs@units@boost@@U?$scale@$09V?$static_rational@$02$00@units@boost@@@34@@units@boost@@U?$list@Usecond_base_unit@si@units@boost@@U?$list@Uampere_base_unit@si@units@boost@@U?$list@Ukelvin_base_unit@si@units@boost@@U?$list@Umole_base_unit@si@units@boost@@U?$list@Ucandela_base_unit@si@units@boost@@U?$list@Uradian_base_unit@angle@units@boost@@U?$list@Usteradian_base_unit@angle@units@boost@@Udimensionless_type@34@@34@@34@@34@@34@@34@@34@@23@@34@@units@boost@@@23@X@34@B) already defined in stdafx.obj Any insights would be appreciated. Thanks, David

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Possible bug in archive/codecvt_null.hpp
by Matthieu Brucher 06 Jan '09

06 Jan '09

Hi, I'm trying to compile Boost 1.37 with PGI 7.0-7 (which does not support some SSE2 instructions, but this is easily managed) and I run into a missing ";" in archive/codecvt_null.hpp when no STD namespace is available: 25 #if defined(BOOST_NO_STDC_NAMESPACE) 26 using ::codecvt; 27 using ::mbstate_t; 28 using ::size_t 29 #endif Line 28 should end with a comma. Matthieu -- Information System Engineer, Ph.D. Website: http://matthieu-brucher.developpez.com/ Blogs: http://matt.eifelle.com and http://blog.developpez.com/?blog=92 LinkedIn: http://www.linkedin.com/in/matthieubrucher

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isnan stopped working
by Thijs Koerselman 06 Jan '09

06 Jan '09

isnan() and family seems to have stopped working in my code. The only thing I can remember is updating from 1.36 to 1.37. Any idea why the following wouldn't work? float nan = FP_NAN; int ret = 0xdeadbeef; ret = (boost::math::isnan)(nan); isnan never returns anything. The value of ret is still 0xdeadbeef after invoking isnan() I'm on OSX10.5.6 using XCode 3 if that helps. Thijs

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proto: BOOST_PROTO_AUTO
by Kim Kuen Tang 06 Jan '09

06 Jan '09

Hi all, i have a question and a problem. The problem is that i would like to write code like: domain=Domain([0,1]*[0,1]); where Domain([0,1]*[0,1]) is an expression created with proto. But of course this line of code is illegal, because i have to provide the type of this expression Domain([0,1]*[0,1]). So i have to write something like this: Domain([0,1]*[0,1])::type domain=Domain([0,1]*[0,1]); Is this correct? Now the question: To avoid code like above is this what the macro BOOST_PROTO_AUTO is for? Can i write BOOST_PROTO_AUTO( domain,Domain([0,1]*[0,1]) ); . Thanks in advance, Kim Tang

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Boost preprocessor question
by Michiel Helvensteijn 06 Jan '09

06 Jan '09

I'm looking for a way to write certain kinds of classes without duplication or unnecessary verbosity. Because there will be many of them in a single file and I want them to be readable. I'm trying to decide if I should use the preprocessor or if I should write a script to do the translation before compilation. I would like something like this (how I think it might look): CLASS(Foo, FROM(Bar)) CONSTRUCT() CONSTRUCT(PAR(int, a, A), PAR(bool, b, B)) int A; bool B; END_CLASS to automatically become something like this: class Foo : public Bar, public shared_from_this<Foo> { private: Foo() {} public: static shared_ptr<Foo> construct() { return shared_ptr<Foo>(new Foo()); } private: Foo(int a, bool b) : A(a), B(b) {} public: static shared_ptr<Foo> construct(int a, bool b) { return shared_ptr<Foo>(new Foo(a, b)); } int A; bool B; }; Is such a thing possible? You see, there are a few things happening there: * Variable length list, reproduced more than once in different ways. * Foo is remembered to use in the constructor name. What would the original code look like if we could make this work? And is there something in the boost preprocessor library that can help me? Thanks in advance! -- Michiel Helvensteijn

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