January 2012 - Boost - lists.preview.boost.org

[#pragma once]
by Sid Sacek 18 Nov '12

18 Nov '12

I've worked with the MSVC, Sun and GCC compilers. Each one of them supports #pragma once. Is there any reason to wrap this pragma within #ifdefs? Are there any compilers out there today that don't support this #pragma? #if defined( _MSC_VER ) && ( _MSC_VER >= 1020 ) # pragma once #endif Could we change this coding pattern so that it no longer looks like MSVC is being selfish? -Sid Sacek

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[config] explicit call of operator templates / msvc bug workaround
by Stefan Strasser 10 Oct '12

10 Oct '12

Hi, is there already a macro in Boost.Config that allows you to insert the "template" keyword in the following code for those compilers that require it? struct functor{ template<class T> void operator()(); }; template<class F> void g(F f){ f.template operator()<int>(); //(1) works with GCC and comeau f.operator()<int>(); //(2) works with MSVC } this apparently only applies to operator calls. MSVC accepts both (1) and (2) for regular functions. (instantiating the operator template with an object of type T as argument, like mpl::for_each does, is not an option. I can't construct T.) thanks, Stefan

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[test] Trunk broken: What happened to test_exec_monitor?
by John Maddock 21 Sep '12

21 Sep '12

Testing on Trunk is apparently broken as the test_exec_monitor target has been removed from Boost.Test Trunk as of revision #74642. A quick grep shows 22 Jamfiles and over 200 targets dependent upon this. Whats happened? John.

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[type_traits] has_equal_to< std::vector<T> > always true_
by lcaminiti 15 Jul '12

15 Jul '12

-- View this message in context: http://boost.2283326.n4.nabble.com/boost-type-traits-has-equal-to-std-vecto… Sent from the Boost - Dev mailing list archive at Nabble.com.

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hex/unhex()?
by Olaf van der Spek 19 Jun '12

19 Jun '12

Hi, Does Boost have hex/unhex() that support std::string? I can't find them and I think they'd be quite handy to have. -- Olaf

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status of sp_counted_base_solaris.hpp
by Graham Bennett 07 Jun '12

07 Jun '12

Hi all, I'm interested in getting boost::shared_ptr to use atomic ops on Solaris. I notice there is an implementation using the OS-provided atomics in boost/detail/sp_counted_base_solaris.hpp, but it doesn't seem to be included. According to this thread: http://lists.boost.org/Archives/boost/2006/07/107144.php, it seems the reason might be that it wasn't possible to come up with a proper preprocessor condition to include it on the right versions of Solaris. I'm considering modifying my boost installation to include this header on Solaris - does anyone know of any issues with the code, or can they confirm that it has been well tested? Are there any other reasons for its omission? Thanks, Graham -- Graham Bennett

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[fusion] Trouble using BOOST_FUSION_ADAPT_ADT with boost::fusion::operator<
by GOODHART, TAYLOR 17 May '12

17 May '12

Hi all, I'm attempting to adapt a third-party struct into a fusion sequence using BOOST_FUSION_ADAPT_ADT to get access to a nice operator<. Unfortunately compilation fails and I'm not sure if it's a bug or me using the library incorrectly. As best I can read the error message, it looks like the code is attempting to compare adt_attribute_proxy structs instead of the values represented by these. Below is some code that demonstrates the problem. Can anybody help me out? Thanks, Taylor #include <boost/fusion/adapted/adt/adapt_adt.hpp> #include <boost/fusion/adapted/struct/define_struct.hpp> #include <boost/fusion/adapted/struct/adapt_struct.hpp> #include <set> #include <string> #include <boost/fusion/sequence/comparison/less.hpp> struct test1 { std::string s; const std::string & getS() const { return s; } void setS( const std::string & s_) { s = s_; } }; BOOST_FUSION_ADAPT_ADT( test1, (const std::string &, const std::string &, obj.getS(), obj.setS(val)) ) BOOST_FUSION_DEFINE_STRUCT( , test2, (std::string, s) (int, a) ) struct test3 { std::string s; }; BOOST_FUSION_ADAPT_STRUCT( test3, (std::string, s) ) using boost::fusion::operator<; int main( int argc, char * argv[]) { //Fails /*std::set<test1> destinations1; destinations1.insert(test1());*/ std::set<test2> destinations2; destinations2.insert(test2()); std::set<test3> destinations3; destinations3.insert(test3()); return 0; }

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[contract] syntax redesign
by Lorenzo Caminiti 04 May '12

04 May '12

Hello all, After a long time of inactivity for Boost.Contract, I am considering how to re-design its macro syntax to make it simpler. I can eliminate a large number of extra parenthesis based on a few pp tricks I've learned in processing Boost.Local's `const bind(type)& var`. Plus, I can provide (optional) support for variadics macros so to use comma-separated pp tuplets instead of parenthesized pp sequences on preprocessors with variadics. For example, I _think_ (but I've not implemented this yet) that I can simplify the syntax like this: #include <contract.hpp> #include <vector> #include "myvector/pushable.hpp" // Wrapper class that adds contracts to std::vector. CONTRACT_CLASS( template( typename T ) class (myvector) extends( public pushable<T> ) // Subcontracting. ) { CONTRACT_CLASS_INVARIANT( empty() == (size() == 0) // More invariants here (comma separated)... ) CONTRACT_FUNCTION( public void (push_back)( (const T&) element ) precondition( size() < max_size() // More preconditions here (comma separated)... ) postcondition( auto old_size = CONTRACT_OLDOF(size()), // Old value. size() == old_size + 1 // More postconditions here (comma separated)... ) ) { vector_.push_back(element); // Implementation. } // Rest of the class here (with more contracts if needed)... public: typedef typename std::vector<T>::size_type size_type; size_type size(void) const { return vector_.size(); } size_type max_size(void) const { return vector_.max_size(); } bool empty(void) const { return vector_.empty(); } const T& back(void) const { return vector_.back(); } private: std::vector<T> vector_; }; For a side-by-side comparison with N1962 syntax: http://svn.boost.org/svn/boost/sandbox/contract/libs/contract/doc/html/inde… For a comparison of the entire std::vector (plus Boost.ConceptCheck concepts): http://svn.boost.org/svn/boost/sandbox/contract/libs/contract/doc/html/cont… For a comparison for all Boost.Contract features (plus Boost.ConceptCheck concepts and Boost.Parameter named parameters): http://svn.boost.org/svn/boost/sandbox/contract/libs/contract/doc/html/cont… (Don't pay attention to the rest of the docs that are way out of date.) A few notes: * Extra parenthesis are still needed around class and function names. * Extra parenthesis are still needed around types (like for the parameter `(T) element`) but only if the type is not a C++ keyword (no parenthesis needed aournd int, double, void, etc) or it contains a symbol (parenthesis needed if & or * are used `(int&) x`, etc). * In postconditions, the `auto old_size = CONTRACT_OLDOF(size())` only copies the vector size (and not the entire vector :)) ). Similarly, `auto result = return` can be used to access the return value for non-void functions. (The `auto ...` is parsed by the pp and it's implemented using Boost.Typeof so no C++0x is required.) * Template declaration (but not instantiation) angular parenthesis <> are replaced by round parenthesis (). All of this _should_ be implementable in pure ISO C++. What do you think? Based on the discontent that the previous "parenthesized" syntax generated among Boosters, the key question is: Would you consider this new syntax usable?? Thanks, --Lorenzo

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Looking for some "real world" extended precision integer arithmetic tests
by John Maddock 23 Mar '12

23 Mar '12

Folks, I'm continuing to add to the multiprecision arithmetic library in the sandbox (under "big_number"), and I've just added a Boost licensed fixed-precision integer type which on Win32 at least looks to be very competitive with GMP for reasonable numbers of bits (up to about 1024), see http://svn.boost.org/svn/boost/sandbox/big_number/libs/multiprecision/doc/h… However, as we all know there are lies damn lies and performance stats ;-) Plus the test results I have above ignore the effect of memory allocations (needed by libtommath and GMP, but not the fixed_int code - which in theory should make it faster still). So I'd be really interested to put the type through it's paces with some real world code that really thrashes an extended precision integer type. Any suggestions? Anything in Boost? Thanks in advance, John.

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[config] local types as template params
by Lorenzo Caminiti 22 Mar '12

22 Mar '12

Hello all, Is it possible to add a macro BOOST_CONFIG_LOCAL_TYPES_AS_TEMPLATE_PARAMS to Boost.Config to indicate if local types can be passed as template parameters? 1) Boost.Closure (formerly, Boost.Local) implements some optimizations when local types can be passed as template parameters. 2) C++11 always allows to pass local types as template parameters. 3) Local types cannot be passed as template parameters on C++03 instead but some C++03 compilers MSVC 8 (and older?) allow it anyway. // If it is possible to pass local types (classes, etc) as template parameters. // This is not possible in pure C++03 but it is possible in some C++03 // extensions (MSVC 8.0) and with C++11 (GCC >= 4.5.x -std=c++0x). #if (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ > 4)) && \ defined(__GXX_EXPERIMENTAL_CXX0X__) // From GCC 4.5.x when -std=c++0x specified. # define BOOST_LOCAL_TYPES_AS_TEMPLATE_PARAMS #elif defined(_MSC_VER) // For (all?) MSVC (tested on MVSC 8.0). # define BOOST_LOCAL_TYPES_AS_TEMPLATE_PARAMS #endif All, can you please try to compile the following example on different compilers/versions and let me know the outcome? If this example compiles successfully then the specific compiler supports local types as template parameters: #include <algorithm> #include <iostream> int main() { struct s { void operator()(int x) { std::cout << x << std::endl; } } l; int nums[] = {1, 2, 3}; std::for_each(nums, nums + 3, l); return 0; } For example, this compiles on GCC >= 4.5.x w/ C++0x extensions enabled and on MSVC 8.0- does it compile on all MSVC versions? Thanks. --Lorenzo

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