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[Review Results] Named Parameters Library
by Doug Gregor 06 Dec '04

06 Dec '04

The Named Parameters Library has been accepted into Boost. Congratulations to the authors, David Abrahams and Daniel Wallin. The vast majority of reviews were positive, although most reviewers requested additional documentation. Here is a list of the most important/commonly-requested changes or additions to the library: - More documentation! Specifically, + Automatic overload generation should go into the tutorial + Document operator, + Performance data (what's the cost?) + Reference section + "Best practices" section. - Add a metafunction for getting the type of a parameter, e.g., param_type<Params, width_t>::type. - Add test cases for the automatic overload generation macros. - Fix the BOOST_NAMED_PARAMS_MAX_ARITY bug; Cromwell Enage provided a solution. Doug Gregor Review Manager

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Anyone interested in a virtual constructor lib?
by Roland Schwarz 06 Dec '04

06 Dec '04

As a byproduct of my current work I factored out a small utility library that implements a virtual constructor. The implementation is based on boost::any and typeid(...).name(). It features dynamic creation of objects by name (string), and allows for default and custom constructors beeing called. It could be used as the basic step to object deserialization from a file, creation of operating system dependent implementations, or allow a library to instantiate user-pluggable classes. The design is inspired by the Io_obj example from Stroustrup's book on C++ programming. A small example to show the usage: #include <string> #include <iostream> #include "dynanew.hpp" using namespace dynanew; // a simple class hierarchy with abstact base class struct shape { virtual void draw() = 0; }; struct square : public shape { virtual void draw() { std::cout << "I am a square" << std::endl; } }; struct circle : public shape { circle() : radius(0) {} circle(double dr) : radius(dr) {} virtual void draw() { std::cout << "I am a circle of radius: " << radius << std::endl; } double radius; }; // create the type map TYPE_MAP(shape); // square with default constructor TYPE_REGISTER(shape, square); // circle with custom constructor taking a double parameter TYPE_REGISTER1(shape, circle, double); // circle with default constructor TYPE_REGISTER(shape, circle); int main(int argc, char* argv[]) { std::string type; type = "square"; shape* ps1 = dynamic_new<shape>(type); shape* ps2 = dynamic_new<shape>("circle", 20.0); shape* ps3 = dynamic_new<shape>("circle"); shape* ps4 = dynamic_new<shape>("square", 10.0); if (ps1) ps1->draw(); // prints: I am a square if (ps2) ps2->draw(); // prints: I am a circle of radius: 20.0 if (ps3) ps3->draw(); // prints: I am a circle of radius: 0.0 if (ps4) ps4->draw(); // does nothing since no ctor available delete ps1; delete ps2; delete ps3; delete ps4; return 0; } regards, Roland

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date-time out of whack?
by Victor A. Wagner Jr. 06 Dec '04

06 Dec '04

The program that causes this error used to compile (until a few days ago) I'm using the cvs HEAD c:\boost\include\boost-1_32\boost\iterator\iterator_facade.hpp(326) : error C2664: 'boost::implicit_cast' : cannot convert parameter 1 from 'const std::string *__w64 ' to 'boost::mpl::identity::type' with [ T=boost::detail::operator_arrow_result,std::basic_string,std::allocator>::const_iterator,std::string>,std::string,boost::detail::minimum_category::type>::type,const std::string &>::value_type,boost::iterator_facade,std::basic_string,std::allocator>::const_iterator,std::string>,std::string,boost::detail::minimum_category::type>::type,const std::string &>::reference,boost::iterator_facade,std::basic_string,std::allocator>::const_iterator,std::string>,std::string,boost::detail::minimum_category::type>::type,const std::string &>::pointer>::type ] Conversion loses qualifiers c:\boost\include\boost-1_32\boost\iterator\iterator_facade.hpp(325) : while compiling class-template member function 'boost::detail::operator_arrow_result::type boost::detail::operator_arrow_result::make(Reference)' with [ ValueType=boost::iterator_facade,std::basic_string,std::allocator>::const_iterator,std::string>,std::string,boost::detail::minimum_category::type>::type,const std::string &>::value_type, Reference=boost::iterator_facade,std::basic_string,std::allocator>::const_iterator,std::string>,std::string,boost::detail::minimum_category::type>::type,const std::string &>::reference, Pointer=boost::iterator_facade,std::basic_string,std::allocator>::const_iterator,std::string>,std::string,boost::detail::minimum_category::type>::type,const std::string &>::pointer ] c:\boost\include\boost-1_32\boost\iterator\iterator_facade.hpp(642) : see reference to class template instantiation 'boost::detail::operator_arrow_result' being compiled with [ ValueType=boost::iterator_facade,std::basic_string,std::allocator>::const_iterator,std::string>,std::string,boost::detail::minimum_category::type>::type,const std::string &>::va lue_type, Reference=boost::iterator_facade,std::basic_string,std::allocator>::const_iterator,std::string>,std::string,boost::detail::minimum_category::type>::type,const std::string &>::reference, Pointer=boost::iterator_facade,std::basic_string,std::allocator>::const_iterator,std::string>,std::string,boost::detail::minimum_category::type>::type,const std::string &>::pointer ] c:\boost\include\boost-1_32\boost\token_iterator.hpp(41) : see reference to class template instantiation 'boost::iterator_facade' being compiled with [ Derived=boost::token_iterator,std::basic_string,std::allocator>::const_iterator,std::string>, Value=std::string, CategoryOrTraversal=boost::detail::minimum_category::type>::type, Reference=const std::string & ] c:\boost\include\boost-1_32\boost\date_time\date_parsing.hpp(119) : see reference to class template instantiation 'boost::token_iterator' being compiled with [ TokenizerFunc=boost::char_delimiters_separator, Iterator=std::basic_string,std::allocator>::const_iterator, Type=std::string ] c:\boost\include\boost-1_32\boost\date_time\gregorian\parsers.hpp(24) : see reference to function template instantiation 'date_type boost::date_time::parse_date(const std::string &,int)' being compiled with [ date_type=boost::gregorian::date ] 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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Boost.FileSystem, problem with exists()
by Martin Slater 06 Dec '04

06 Dec '04

Hi, I've been using boost.filesystem and have come up on a problem with exists(). Basically on a windows system it will return true if asking whether a file exists on a non-existent share. The problem is at, operations_posix_windows.cpp:327. There should (?) be an additional check against ERROR_BAD_NETPATH as well. The fuzziness of this function is quite disturbing as shown by the following comment in the code return false; // GetFileAttributes failed because the path does not exist // for any other error we assume the file does exist and fall through, // this may not be the best policy though... (JM 20040330) The windows docs don't really help that much by not specify exactly what the failures can be though. Personally I think it should always return false on GetAttributes() error to avoid false positives and the expense of the possible false negatives, but we need a list of all possible errors to be sure that this is the right thing to do. Oh and any chance you can put in serialization support for boost::filesystem::path? I've done it locally and the code is trivial but it would be nice to have it out the box. Anyhow, thanks for a great library (filesystem and the rest of boost). cheers martin

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A few more filesystem documentation corrections
by Edward Diener 06 Dec '04

06 Dec '04

Here are a few more grammatical corrections to the excellent filesystem documentation. Default Name Check mechanism Dangers second sentence: "Since global variables are considered harmful [Wulf-Shaw-73], class path allows the default name check function can be set only once, and only before the first use." should be: "Since global variables are considered harmful [Wulf-Shaw-73], class path allows that the default name check function can be set only once, and only before the first use." or "Since global variables are considered harmful [Wulf-Shaw-73], class path allows the default name check function to be set only once, and only before the first use." Rationale Const vs non-const returns last sentence: "A requirement that path::iterator not be a non-class type was added to eliminate errors non-const iterator errors." should be: "A requirement that path::iterator not be a non-class type was added to eliminate non-const iterator errors." or better: "A requirement that path::iterator be a class type was added to eliminate non-const iterator errors." Finally, in operations.hpp, links on "class directory_iterator" and "other functions" to their explanations further down the page do not work using IE, Netscape, or Opera, so I imagine some HTML error.

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Filesystem documentation error
by Edward Diener 06 Dec '04

06 Dec '04

The documentation to filesystem is outstanding. Congratulation Mr. Dawes ! I did find an error, however. In the class documentation to path.hpp there are two default_name_check member functions. In the specific documentation for default_name_check, there is only a single default_name_check mentioned and the return value in the declaration of the specific documentation has 'void' even while the "Returns:" says otherwise and correctly matches the return value given for either one of the default_name_checks given in the class documentation.

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BOOST_FOREACH questions
by Vladimir Prus 05 Dec '04

05 Dec '04

Eric, I've some questions about BOOST_FOREACH (which is pretty cool, BTW). 1. Is it possible to use typeof on gcc, to avoid any possible overhead? While you've posted some results which show that gcc generally can optimise it very well, I'd like to be 100% sure). Something like: #define FOR_EACH(var, container) \ for(typeof(container.begin()) _for_each_i = container.begin(),\ _for_each_e = container.end();\ _for_each_i != _for_each_e; ++_for_each_i)\ if(bool _for_each_continue = false) {}\ else\ for(var = *_for_each_i; !_for_each_continue; _for_each_continue=true) which works perfectly for me. 2. Any chance that BOOST_FOREACH((pair<int, int> p), container) will work? I don't know how to make it work without require paranthethis in all cases, but maybe there's a smart trick. 3. Is it possible that you place this to sandbox, for easier access? - Volodya

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[Boost-bugs] [ boost-Bugs-1079444 ] type_traits headers use #include ""
by SourceForge.net 05 Dec '04

05 Dec '04

Bugs item #1079444, was opened at 2004-12-05 08:59 Message generated for change (Tracker Item Submitted) made by Item Submitter You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=107586&aid=1079444&group_… Category: None Group: None Status: Open Resolution: None Priority: 5 Submitted By: Nobody/Anonymous (nobody) Assigned to: Nobody/Anonymous (nobody) Summary: type_traits headers use #include "" Initial Comment: The various type_traits headers (as of boost 1.32.0) use #include "" directives while the rest of boost headers uses #include <>. For example the use of #include "" in boost/type_traits/ add_reference.hpp compared to the use of #include <> in boost/ mpl/bool.hpp . ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=107586&aid=1079444&group_… ------------------------------------------------------- SF email is sponsored by - The IT Product Guide Read honest & candid reviews on hundreds of IT Products from real users. Discover which products truly live up to the hype. Start reading now. http://productguide.itmanagersjournal.com/ _______________________________________________ Boost-bugs mailing list Boost-bugs(a)lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/boost-bugs

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Deserialization issue
by Jared McIntyre 05 Dec '04

05 Dec '04

I have a class that I am serializing using the non-intrusive method. It serializes just fine, but when I code the input stream, the compiler complains that the class doesn't implement the serialize function (which is, of course, true since I'm am doing the non-intrusive method on this class). Any idea what could be going wrong? The class I'm wrapping is being serialized as part of another class (if that helps at all). Visual Studio 7.1 Boost 1.32.0 tar ball Wide character XML output Jared McIntyre

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Front page redesign...
by Rene Rivera 05 Dec '04

05 Dec '04

Fellow Boosters, Well I must say I've been smiling all day :-) Thanks for the encouraging feedback. And I've been putting finishing touches on my design hopefully coming up with something everyone can enjoy. I have two different sample for you to gander at. The first is the simple clean version... http://redshift-software.com/~grafik/boost/index.htm The second adds some background flair to the page... http://redshift-software.com/~grafik/boost/index_code.htm And for those with CSS switching browser, there's an alternate CSS on each of those which displays the page without any CSS. Just to show that everything is done in thee CSS ;-) Enjoy. Have a good weekend, and all that. -- -- Grafik - Don't Assume Anything -- Redshift Software, Inc. - http://redshift-software.com -- rrivera/acm.org - grafik/redshift-software.com - 102708583/icq

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