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enable_if question
by John Maddock 08 May '12

08 May '12

Folks I'm having some difficulties understanding the subtleties of enable_if, consider: using namespace boost; template <unsigned B> struct dummy {}; template <unsigned B, class Integer> typename boost::enable_if<mpl::and_<is_signed<Integer>, mpl::bool_<(sizeof(Integer) <= sizeof(long))> > >::type bar(dummy<B>&, const Integer&) { } template <unsigned B, class Integer> typename boost::enable_if<mpl::and_<is_unsigned<Integer>, mpl::bool_<(sizeof(Integer) <= sizeof(long))> > >::type bar(dummy<B>&, const Integer&) { } Then calling: dummy<2> d; bar(d, 2); Leads to an ambiguity between the two overloads (both gcc and VC++10), how can that be? However, changing the condition to: template <unsigned B, class Integer> typename boost::enable_if<mpl::and_<is_signed<Integer>, mpl::bool_<(B || !B) && (sizeof(Integer) <= sizeof(long))> > >::type bar(dummy<B>&, const Integer&) { } template <unsigned B, class Integer> typename boost::enable_if<mpl::and_<is_unsigned<Integer>, mpl::bool_<(B || !B) && (sizeof(Integer) <= sizeof(long))> > >::type bar(dummy<B>&, const Integer&) { } "fixes" things. But this fix isn't always possible. Thoughts? Thanks, John.

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[preprocessor] Chaos: Auto macros incorrectly deduces the recursion state
by paul Fultz 08 May '12

08 May '12

Hello, I am not sure if this is the most appropriate place to post this, but I do know the author frequents this mailing list often. Well, when I run this code: #define FIXED(s, n, text) text #define TTP(s, n, id) \ template< \ CHAOS_PP_AUTO_ENUM( \ CHAOS_PP_INC(n), FIXED, class \ ) \ > class id ## n \ /**/ CHAOS_PP_AUTO_ENUM(3, TTP, T) // template<class> class T0, // template<class, class> class T1, // template<class, class, class> class T2 It expands to: template< CHAOS_IP_AUTO_ENUM_1( 1, FIXED, class ) > class T0 , template< CHAOS_IP_AUTO_ENUM_1( 2, FIXED, class ) > class T1 , template< CHAOS_IP_AUTO_ENUM_1( 3, FIXED, class ) > class T2 Showing CHAOS_IP_AUTO_ENUM_1 is incorrect, and its why it won't expand since its trying to be expanded recursively. It should be CHAOS_IP_AUTO_ENUM_2 instead. I'm not sure why it incorrectly deduces the recursion state. TTP is not a deferred expression. Any ideas? Thanks, Paul Fultz II

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Aspen Meadows Resort suite available for up to 4 nights for C++Now Conference
by Pdruck 08 May '12

08 May '12

Hi. I reserved a suite at Aspen Meadows Resort for 4 nights, for the C++Now conference; Sunday night, May 13 – Wed night, May 16, leaving Thurs. May 17. But due to last minute pressing events in the office, I have to cancel my registration. Propose to switch my reservation to whomever might be attending. Win-win. I don’t lose a heft cancellation fee. You get a beautiful suite (having been there previously) and conveniently located to the conference at Physics Center. Regards. Phil

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Iterator Range and operator==
by Olaf van der Spek 08 May '12

08 May '12

Hi, What do you expect this code to do? Is b true or false? And why? Is this expected behaviour? #include <boost/range/iterator_range.hpp> #include <string> int main() { std::string s = "Olaf"; boost::iterator_range<std::string::iterator> r(s); bool a = r == s; bool b = r == "Olaf"; assert(a); assert(b); return 0; } -- Olaf

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[bind] variant arg list template functions could have a forward declaration as doc & coding suggeustion
by Huang Huan 08 May '12

08 May '12

Hi all, Before I do some change, no suggestion when I coding with Boost.Bind. This is a big disadvantage for learning & using. Variant arg list template functions as follow are there in so many boost code file. // template<class F, class A1, ... class An> // X foo(F f, A1 a1, ... An an); template<class F> X foo(F f) { ... } template<class F, class A1> X foo(F f, A1 a1) { ... } template<class F, class A1, class A2> X foo(F f, A1 a1, A2 a1) { ... } ... Some code like the comment, the forward declaration could be good doc & coding suggestion, such as following: template<class F /*, class A1, ... class An */> X foo(F f /*, A1 a1, ... An an */); OR template<class F, class A1, class A2 /*, ... */> X foo(F f, A1 a1, A2 a2, ... ); OR template<class F /*... */> // may no cxx11 X foo(F f , ... ); This may like BOOST_CONTAINERS_PERFECT_FORWARDING Becase of the template grammar, this forward declaration has no implementation. The code is ONLY for coding suggestion & doc. As an example [boost][bind] When I write the code boost::bind( _ ) I want the suggestions as follow ______________________________________________ | [1 of 3] _bi::bind_t<_bi::unspecified, F, L> bind(F f, ...) | |_____________________________________________| A more difficulty is boost bind has a BOOST_BIND for redefine the name. my patch as follow: =================================================================== --- bind.hpp (revision 77278) +++ bind.hpp (working copy) @@ -1289,6 +1289,17 @@ #ifndef BOOST_BIND #define BOOST_BIND bind + +template<class R, class F, class L> + _bi::bind_t<R, F, L> + bind(F f, ...); +template<class R, class F, class L> + _bi::bind_t<R, F, L> + bind(boost::type<R>, F f, ...); +template<class F, class L> + _bi::bind_t<_bi::unspecified, F, L> + bind(F f, ...); + #endif // generic function objects

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Boost Threads - x86 Platforms / 64 bits compilation in Managed/Unmanaged Code / Visual Studio 2010 / Windows SDK 7.1 /clr
by Guillaume Rembert 07 May '12

07 May '12

As I had lots of issues to include boost thread libraries in a windows 64 bits code generated under Visual Studio 2010, here are the different steps to follow in order to get it compiling and executing quickly (mix of lots of the different specific posts). I could not find an easy, up to date procedure for this. This has been tested with Boost 1_49_0 release, Visual Studio 2010, Windows SDK 7.1 and Microsoft .NET 4. - Download 64 bits libraries, as binaries: http://boost.teeks99.com/ + unzip in a dedicated folder (for the example C:\boost\lib64) - Download boost headers and source code: http://sourceforge.net/projects/boost/files/boost/1.49.0/ + unzip in a dedicate folder (for the example C:\boost) - Set the project not to use precompiled headers + compilation with /clr to mix managed and unmanaged code - Add the headers path to the project additional include directories (in the example C:\boost) - Add the compiled libraries path to the linker additional library directories (in the example C:\boost\lib64) - Add to your project the following lines (force dynamic linking): #define BOOST_ALL_DYN_LINK #define BOOST_THREAD_USE_DLL #define BOOST_LIB_DIAGNOSTIC #include <boost/thread.hpp> --> Just compile and execute, it should not give any problems. The first line (#define BOOST_ALL_DYN_LINK) solves the following error I had: An unhandled exception of type 'System.TypeInitializationException' occurred in Unknown Module. Additional information: The type initializer for '<Module>' threw an exception.

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[generic] status?
by lcaminiti 06 May '12

06 May '12

Hello all, What's the status of Matt Calabrese's Boost.Generic library? I was looking at the similarities between Boost.Generic and Boost.Contract syntax, and I think the following syntax can be implemented to define concepts, concepts_maps, axioms, etc CONTRACT_CONCEPT( concept (Iterator) ( typename X ) extends( Semiregular<X> ) ( typename(MoveConstructible) reference, as typename X::reference , typename(MoveConstructible) postinc_result , requires HasDereference<postinc_result> , (reference) operator(*)(deref) ( X& ) , (reference) operator(*)(deref) ( X&& ) , (X&) operator(++)(preinc) ( X& ) , (postinc_result) operator(++)(postinc) ( X&, int ) ) ) More examples here (auto concepts, concept maps, axioms, etc): http://contractpp.svn.sourceforge.net/viewvc/contractpp/trunk/doc/html/cont… If there was real interest using this syntax to define concepts, either the syntax could replace the on of Boost.Generic or Boost.Contract could provide the syntax and then use Boost.Generic behind the scene to actually define the concepts (same as Boost.Contract now does for Boost.Parameter). What do you think? Thanks. --Lorenzo -- View this message in context: http://boost.2283326.n4.nabble.com/boost-generic-status-tp4611363.html Sent from the Boost - Dev mailing list archive at Nabble.com.

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[concept] typenames vs. typedefs
by lcaminiti 06 May '12

06 May '12

Hello all, I have questions about concepts (it's related to Boost.ConceptCheckign and Boost.Generic, but it's really just about the concept syntax that was proposed and never adopted for C++11). What's the difference between typename new_type = old_type and typedef old_type new_type? Why are they both allowed? For example, what's the difference between this: auto concept HasFind < typename T > { typename key_type = typename T::key_type; // use typename typename mapped_type; std::pair<key_type, mapped_type> find ( T const&, key_type const& ); } And this: auto concept HasFind < typename T > { typedef typename T::key_type key_type; // use typedef typename mapped_type; std::pair<key_type, mapped_type> find ( T const&, key_type const& ); } Thanks a lot. --Lorenzo -- View this message in context: http://boost.2283326.n4.nabble.com/boost-concept-typenames-vs-typedefs-tp46… Sent from the Boost - Dev mailing list archive at Nabble.com.

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question about C++11 guidelines
by Eric Niebler 06 May '12

06 May '12

Say I'm rewriting an existing Boost library and targeting C++11 users. I plan to ship C++03 and C++11 versions of my library side-by-side, so back-compat isn't an issue for the new code. Is there a reason to prefer using Boost's versions of utilities like enable_if, type traits, integral constant wrappers (e.g. mpl::int_), tuples, etc., over the now-standard ones? I'm leaning toward using std:: where I can, and falling back on Boost's versions only when there is a compelling reason. -- Eric Niebler BoostPro Computing http://www.boostpro.com

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Latest version and status of lockfree
by Julien Nitard 06 May '12

06 May '12

Hi All, Where can I find the latest version of boost.lockfree ? There's nothing in the sandbox or the vault (it seems). The latest commit on Tim's public git repo was done more than 6 month ago. Now that atomic has been accepted, are there any roadblocks to have boost.lockfree released ? Many thanks, Julien

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