January 2005 - Boost-users - lists.preview.boost.org

Re: [Boost-users] boost::tuple problem
by Victor A. Wagner Jr. 24 Jan '05

24 Jan '05

At Saturday 2005-01-22 08:22, you wrote: > hello everyone, >     what's the difference between "tuple<int> t;"  > and  " tuple<int> t();" >why > tuple<int> t; > cout<<t; >is ok. >But > tuple<int> t(); this declares a function named t which takes no arguments and returns a tuple<int> it does NOT define a variable named t. > cout<<t; >make a link error. >I'm using >vs.net2003__________________________________________________________________»¶ÓÊ¹ÓÃACMAIL >ÓÊ¼þÏµÍ³ > > > >_______________________________________________ >Boost-users mailing list >Boost-users(a)lists.boost.org >http://lists.boost.org/mailman/listinfo.cgi/boost-users Victor A. Wagner Jr. http://rudbek.com The five most dangerous words in the English language: "There oughta be a law"

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Serialization problem loading a vector of items
by Bill Lear 24 Jan '05

24 Jan '05

I am curious why loading a vector of items from an input stream fails using one method but works using a slightly different method. Given a load method: template <class T> T* load(std::istream& in) { boost::archive::xml_iarchive ia(in); T* t; ia & BOOST_SERIALIZATION_NVP(t); return t; } and use of it: vector<item>* v = load<vector<item> >(std::cin); I get: uncaught exception: stream error But, when I use this load method: template<class T> void load(std::istream& in, std::vector<T*>& v) { boost::archive::xml_iarchive ia(in); ia >> BOOST_SERIALIZATION_NVP(v); } and use it so: vector<item> v; load(std::cin, v); it works perfectly. Is there some reason the first method should fail? Bill

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serialization library problems with MFC support for OLE Controls
by Muruganathan Annamalai 24 Jan '05

24 Jan '05

hi, Iam using VC6. I had problems using boost serialization library classes with MFC support for OLE controls. This is what I have, #include <afxctl.h> // MFC support for OLE Controls #include <boost/archive/text_oarchive.hpp> #include <boost/archive/text_iarchive.hpp> ............. .............. When I compiled the code I got errors like, :\boost\boost-1_32\boost/archive/basic_text_iprimitive.hpp(72) : error C2039: 'char_type' : is not a member of 'IStream' D:\Devstudio_6.0\VC98\INCLUDE\objidl.h(4049) : see declaration of 'IStream' D:\boost\boost-1_32\boost/archive/basic_text_iprimitive.hpp(121) : see reference to class template instantiation 'boost::archive::basic_text_iprimitive<IStream>' being compiled D:\boost\boost-1_32\boost/archive/basic_text_iprimitive.hpp(72) : error C2065: 'char_type' : undeclared identifier D:\boost\boost-1_32\boost/archive/basic_text_iprimitive.hpp(121) : see reference to class template instantiation 'boost::archive::basic_text_iprimitive<IStream>' being compiled D:\boost\boost-1_32\boost/archive/basic_text_iprimitive.hpp(73) : error C2039: 'traits_type' : is not a member of 'IStream' D:\Devstudio_6.0\VC98\INCLUDE\objidl.h(4049) : see declaration of 'IStream' I think, error is because MFC has class called IStream. And the same name IStream is used as template parameter in the boost class. Is there anything I can do to overcome this problem. annamalai

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implicit conversion
by Benjamin Schmeling 24 Jan '05

24 Jan '05

Hi, I am working on exposing a bigint class to python. Now I've got the problem that methods which take an bigint as an parameter do not accept Python longs. For example: import _PythonLiDIA x=123L; c=_PythonLiDIA.bigint(); _PythonLiDIA.gcd(c,x); Traceback (most recent call last): File "test.py", line 132, in ? _PythonLiDIA.gcd(a,x); Boost.Python.ArgumentError: Python argument types in _PythonLiDIA.gcd(bigint, long) did not match C++ signature: gcd(LiDIA::bigint, LiDIA::bigint) I don't know how to achieve implicit conversion at this point, turning an long automatically into an bigint. The other way round, turning an bigint into long can be realized by defining __long__. Can someone help me please? Benjamin

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program_options usage question
by John Eddy 24 Jan '05

24 Jan '05

Hello, I was wondering if it is possible to have an option for which supplying an argument is optional. For example, suppose I have an executable called myprog and an option "o" that does something. Is it possible to allow both of the following command line syntaxes? myprog --o arg myprog --o Where in the second case I can programatically supply some default value? So the first would instruct the program to take the action associated with the "o" option using the supplied arg and the second would instruct it to take that action using the default argument value. I have been fooling with the default_value and implicit methods but neither seems to do what I want. Thanks, John Eddy johneddy(a)eng.buffalo.edu

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MPL vs BLL
by Roman 24 Jan '05

24 Jan '05

Hi. Any suggestion about mpl vs bll? Will they merge someday, or go concurrently? I haven't found anything on the net about it. I'm using bll currently. Thanks. Roman.

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uBLAS Matrix and Vector IO
by Pascal Bauer 24 Jan '05

24 Jan '05

Hi Boost-Users, Does Anybody know, whether there is a routine to save / read (double) Matrices in a BINARY format? Thanx in Advance. Pascal Bauer

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Tiny bug in boost::threads documentation (bibliographic reference)
by Andreas Wachowski 24 Jan '05

24 Jan '05

Hello, ok, this is, how shall I say it, more of a Knuthish bug, but a bug it is, so I might as well report it: In the bibliography of the boost:threads documentation, a reference is erroneous. It says [Hansen73] ACM Computing Surveys. Vol. 5. No. 4. December, 1983. Per Brinch. "Concurrent Programming Concepts" but instead it should be [Hansen73] ACM Computing Surveys. Vol. 5. No. 4. December, 1973. Per Brinch. "Concurrent Programming Concepts" (1973 instead of 1983) Best regards, Andreas

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passing shared_ptr<> by_value or by-reference?
by Kosta 23 Jan '05

23 Jan '05

Hi! Don't know, if this is a FAQ, but I couldn't find an answer to this question: Is there a common sense about how a shared_ptr<> should be passed to functions/methods: by-value or by-(const-)reference? 1) void test(boost::shared_ptr<A> a); 2) void test(boost::shared_ptr<A>& const a);

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Re: [Boost-users] boost::tuple problem
by Peter Dimov 23 Jan '05

23 Jan '05

heroboy wrote: > hello everyone, >     what's the difference between "tuple<int> > t;"  and  " tuple<int> t();" why > tuple<int> t; > cout<<t; > is ok. > But > tuple<int> t(); > cout<<t; > make a link error. Because tuple<int> t(); is a function returning a tuple<int>.

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