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Type deduction
by Robert Jones 01 Mar '12

01 Mar '12

Is there anything in Boost to help with the type deduction of simple arithmetic expressions? Essentially a C++03 version of template <typename T, typename U> struct deduce { typedef decltype( T / U ) type; }; (I know that wasn't valid code, it's just for exposition) Thx, - Rob.

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[PREDEF] Review for the Boost.Predef library by Rene Riviera
by Joel Falcou 29 Feb '12

29 Feb '12

The review of BOOST.PREDEF by Rene Riviera is scheduled between Monday, February 20th to February 29th. ================ Contents & Scope ================ BOOST.PREDEF defines a set of compiler, architecture, operating system, and library version numbers from the information it can gather of C++ predefined macros or those defined in generally available headers. The idea for this library grew out of a proposal to extend the Boost Config library to provide more, and consistent, information than the feature definitions it supports. What follows is an edited version of that brief proposal. =============== How to get it ? =============== Sources and documentation can be retrieved from http://tinyurl.com/73n6a3k ================ Writing a Review ================ The reviews and all comments should be submitted to the developers list, and the email should have "[PREDEF] Review" at the beginning of the subject line to make sure it's not missed. Please explicitly state in your review whether the library should be accepted. The general review checklist: - What is your evaluation of the design? - What is your evaluation of the implementation? - What is your evaluation of the documentation? - What is your evaluation of the potential usefulness of the library? - Did you try to use the library? With what compiler? Did you have any problems? - How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? - Are you knowledgeable about the problem domain? And finally, every review should answer this question: - Do you think the library should be accepted as a Boost library? Be sure to say this explicitly so that your other comments don't obscure your overall opinion.

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PP: commas issues
by MM 29 Feb '12

29 Feb '12

Hi, I am trying to generate a list of instances of the same template with different pairs of args, to populate a mpl container, with PP so, mpl::vector< tmpl<A::x,A::y>, tmpl<B::x,B::y>, tmpl<C::x, C::y> > i'm having trouble with the commas. I successfully generate the pp sequence (tmpl<A::x,A::y>)(tmpl<B::x,B::y>) (tmpl<C::x, C::y>) but from this to get the enumeration, it's impossible using SEQ_ENUM, because the sequence contains commas MM

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[multi_array] How to specify degenerate at runtime?
by Anton Daneyko 29 Feb '12

29 Feb '12

Greetings to Boosters, I have a 3D multi_array and I would like to make 2D slices using dimensions specified at runtime. I know the index of degenerate dimension and an index of slice, that I want to extract in that degenerate dimension. Currently the ugly workaround looks like that: if (0 == degenerate_dimension) { Slice slice = input_array[boost::indices[slice_index][range()][range()]]; } else if (1 == degenerate_dimension) { Slice slice = input_array[boost::indices[range()][slice_index][range()]]; } else if (2 == degenerate_dimension) { Slice slice = input_array[boost::indices[range()][range()][slice_index]]; } Is there a more beautiful way to construct index_gen object? Something like that: var slicer; for(int i = 0; i < 3; ++i) { if (degenerate_dimension == i) slicer = boost::indices[slice_index]; else slicer = boost::indices[range()]; } Slice slice = input_array[slicer]; It seems each subsequent call to boost::indices::operator[] returns a different type depending on the dimensionality, so there's no way to use a single variable, that can hold the temporary index_gen object.

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iterator_facade with incomplete type as Value argument
by Philipp Moeller 29 Feb '12

29 Feb '12

I've tried writing an iterator with iterator_facade that returns itself as the result of dereference, but the Value template argument requires a complete type because it tries to make a difference between returning by value or reference if Value is_pod (as far as I understand). #include <boost/iterator/iterator_facade.hpp> class iter : public boost::iterator_facade< iter, iter, boost::forward_traversal_tag > { public: void fancy_non_iterator_member(); private: friend class boost::iterator_core_access; void increment() { } bool equal(iter const& other) const { return true; } iter& dereference() const { return const_cast<Derived&>(static_cast<const Derived&>(*this)); } }; Is this the intended behavior of iterator_facade? Is there some workaround? Would such an iterator actually be conforming? -- Philipp Moeller GeometryFactory

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boost python & context manager/with statement
by Avi Bahra 29 Feb '12

29 Feb '12

Does boost python support context management using the with statement? In my case I need to manage __enter__/__exit__ on the c++ side. Could not find any examples for this in the documentation. Any help appreciated. Best regards, Ta, Avi

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Using boost with PathScale v4.x under Linux
by Roberto Fichera 29 Feb '12

29 Feb '12

Hi there, I've compiled the last boost v1.49 against PathScale v4.x compiler under 64bit linux distribution, but when compiling certain library that uses the boost/numeric/interval/rounded_transc.hpp include file, I end up on getting some error regarding asinh(), acosh() and atanh() which were searched in the std namespace. Compiling the same library against g++ or MSVC goes pretty straight without problems. /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp: In member function 'T boost::numeric::interval_lib::rounded_transc_exact<T, Rounding>::asinh_down(const T&)': /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp:42: error: 'std::asinh' has not been declared /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp: In member function 'T boost::numeric::interval_lib::rounded_transc_exact<T, Rounding>::asinh_up(const T&)': /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp:42: error: 'std::asinh' has not been declared /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp: In member function 'T boost::numeric::interval_lib::rounded_transc_exact<T, Rounding>::acosh_down(const T&)': /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp:43: error: 'std::acosh' has not been declared /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp: In member function 'T boost::numeric::interval_lib::rounded_transc_exact<T, Rounding>::acosh_up(const T&)': /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp:43: error: 'std::acosh' has not been declared /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp: In member function 'T boost::numeric::interval_lib::rounded_transc_exact<T, Rounding>::atanh_down(const T&)': /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp:44: error: 'std::atanh' has not been declared /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp: In member function 'T boost::numeric::interval_lib::rounded_transc_exact<T, Rounding>::atanh_up(const T&)': /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp:44: error: 'std::atanh' has not been declared /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp: In member function 'T boost::numeric::interval_lib::rounded_transc_std<T, Rounding>::asinh_down(const T&)': /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp:77: error: 'std::asinh' has not been declared /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp: In member function 'T boost::numeric::interval_lib::rounded_transc_std<T, Rounding>::asinh_up(const T&)': /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp:77: error: 'std::asinh' has not been declared /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp: In member function 'T boost::numeric::interval_lib::rounded_transc_std<T, Rounding>::acosh_down(const T&)': /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp:78: error: 'std::acosh' has not been declared /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp: In member function 'T boost::numeric::interval_lib::rounded_transc_std<T, Rounding>::acosh_up(const T&)': /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp:78: error: 'std::acosh' has not been declared /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp: In member function 'T boost::numeric::interval_lib::rounded_transc_std<T, Rounding>::atanh_down(const T&)': /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp:79: error: 'std::atanh' has not been declared /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp: In member function 'T boost::numeric::interval_lib::rounded_transc_std<T, Rounding>::atanh_up(const T&)': /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp:79: error: 'std::atanh' has not been declared /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp: In member function 'T boost::numeric::interval_lib::rounded_transc_opp<T, Rounding>::asinh_down(const T&)': /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp:122: error: 'std::asinh' has not been declared /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp: In member function 'T boost::numeric::interval_lib::rounded_transc_opp<T, Rounding>::asinh_up(const T&)': /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp:122: error: 'std::asinh' has not been declared /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp: In member function 'T boost::numeric::interval_lib::rounded_transc_opp<T, Rounding>::atanh_down(const T&)': /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp:123: error: 'std::atanh' has not been declared /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp: In member function 'T boost::numeric::interval_lib::rounded_transc_opp<T, Rounding>::atanh_up(const T&)': /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp:123: error: 'std::atanh' has not been declared /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp: In member function 'T boost::numeric::interval_lib::rounded_transc_opp<T, Rounding>::acosh_down(const T&)': /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp:132: error: 'std::acosh' has not been declared /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp: In member function 'T boost::numeric::interval_lib::rounded_transc_opp<T, Rounding>::acosh_up(const T&)': /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp:132: error: 'std::acosh' has not been declared Thus, I had a look in the boost include file boost/numeric/interval/detail/bugs.hpp and look like that apply the patch below fixes the compilation error: --- numeric/interval/detail/bugs.hpp.orig 2012-02-29 10:44:06.876597264 +0100 +++ numeric/interval/detail/bugs.hpp 2012-02-29 10:18:42.831581398 +0100 @@ -25,7 +25,7 @@ #else # define BOOST_NUMERIC_INTERVAL_using_math(a) using std::a # if defined(BOOST_HAS_INV_HYPERBOLIC) -# if defined(__GLIBCPP__) || defined(__GLIBCXX__) +# if defined(__GLIBCPP__) || defined(__GLIBCXX__) || defined(__GLIBC__) # define BOOST_NUMERIC_INTERVAL_using_ahyp(a) using ::a # else # define BOOST_NUMERIC_INTERVAL_using_ahyp(a) using std::a does anyone can comment? Thanks in advance, Roberto Fichera.

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[PREDEF] Review ends today
by Joel Falcou 29 Feb '12

29 Feb '12

The review of Boost.PRedef by Rene Rivera is ending today, February 29th. I recall to all people wanting to submit a formal review to do so. Regards

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Metaprogramming Question
by John M. Dlugosz 28 Feb '12

28 Feb '12

I've not had much opportunity to do much template metaprogramming in my work, but I've kept up with my reading. So, might I get some advice on how to approach this problem? I'm thinking of an assert-like statement that follows the syntax of Boost.Format, thus avoiding the variadic argument list. MY_FANCY_ASSERT (cond, "format string") % arg % arg; works if the macro expands to an unnamed temporary, whose destructor does the interesting work if the first argument is false. my_assert_formatter_type (cond, "cond", __FILE__, __LINE__, "format string") This is easy to do, simply deriving from boost::formatter, I would think. But, I want to avoid doing any work except on failure. This means remembering the arguments including the following %arg stuff, and passing everything through to Boost.Format based on the condition. So I'm thinking that template metaprogramming can let me collect all the arguments (any number of them) into one object, efficiently at compile time. So, what approach should I use? Plain MPL and classic metaprogramming? Fusion? Phoenix? and any concrete suggestions on how to proceed, or pointers to similar works? Thanks, —John

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boost::python handles boost::shared_ptr specially...
by Neal Becker 28 Feb '12

28 Feb '12

Will it just work if I use std::shared_ptr instead?

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