- Boost-users - lists.boost.org

Re: [Boost-users] [STL] Is there a std::abs<>() function? (Max)
by Max 25 Dec '08

25 Dec '08

seconded. But could you tell me where I can find the temple version of AbsoluteValue function you mentioned? Thanks B/Rgds Max ----- Original Message ----- From: Deane Yang To: boost-users(a)lists.boost.org Subject: Re: [Boost-users] [STL] Is there a std::abs<>() function? (Max) Date: 2008-12-23 23:28:08 Scott McMurray wrote: > On Mon, Dec 22, 2008 at 21:06, Max wrote: >> What I need is a template version of abs, not the >> int abs(int) function, to make use of it genericly. >> > > Do you really need a template of it? I can't see why using ADL > wouldn't be enough (with a using declaration for std::abs, to catch > the overloads for scalars from and ). I certainly use template versions of Max, Min, and AbsoluteValue, because I need them for user-defined classes (that represent real numbers) and not just for built-in types. ------------------------------------------------------------------- 新浪空间——与朋友开心分享网络新生活！(http://space.sina.com.cn/ )

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Re: [Boost-users] [boost] [test] Runtime parameter handling subsystem updated
by David Abrahams 25 Dec '08

25 Dec '08

on Tue Dec 23 2008, Gennadiy Rozental <rogeeff-AT-gmail.com> wrote: > Hi, > > I've checked in an update to the runtime parameters handling > subsystem. It's not completely up to my liking yet, but should fare > better than old one. > > From usage prospective you will see major differences in features > supported by command line argument parser (don't worry - everything is > backward compatible). Are these new features documented? -- Dave Abrahams BoostPro Computing http://www.boostpro.com

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Re: [Boost-users] [iterator] transform_iterator
by Max 25 Dec '08

25 Dec '08

But another minor thing that I don't understand is why the template parameters of the transform_iterator and the parameters of its constructor are in the different order. If I were the author, I would feel keeping them in the same order be more natural and more straightforward. Perhaps letting Function be the 1st template parameter make it clearer the behavior of the class? :-) If this is a too stupid question, just ignore. :-) Thanks. B/Rgds Max ----- Original Message ----- From: Steven Watanabe To: boost-users(a)lists.boost.org Subject: Re: [Boost-users] [iterator] transform_iterator Date: 2008-12-25 00:47:36 AMDG Max wrote: > I just came across transform_iterator and found it a useful generic tool. > But is it possible for it to go further to make the following code get > compiled and run as expected? > No. > struct A > { > int i_; > A() : i_(0) {} > explicit A(int i) : i_(i) {} > }; > > const int N = 5; > A a_list[N] = { A(-3), A(1), A(3), A(2), A(-4) }; > > typedef boost::function fn_t; > > // sorting a_list according to the elements' i_ member > std::stable_sort(boost::make_transform_iterator(a_list, fn_t(boost::bind(&A::i_, _1))), > boost::make_transform_iterator(a_list+N, fn_t(boost::bind(&A::i_, _1))), > std::less()); > stable_sort assumes that the sort keys are the same as the objects that it is moving around. In Christ, Steven Watanabe ------------------------------------------------------------------- 新浪空间——与朋友开心分享网络新生活！(http://space.sina.com.cn/ ) ------------------------------------------------------------------- 新浪空间——与朋友开心分享网络新生活！(http://space.sina.com.cn/ )

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Re: [Boost-users] [iterator] transform_iterator
by Max 25 Dec '08

25 Dec '08

Thank you, Watanabe. B/Rgds Max ----- Original Message ----- From: Steven Watanabe To: boost-users(a)lists.boost.org Subject: Re: [Boost-users] [iterator] transform_iterator Date: 2008-12-25 00:47:36 AMDG Max wrote: > I just came across transform_iterator and found it a useful generic tool. > But is it possible for it to go further to make the following code get > compiled and run as expected? > No. > struct A > { > int i_; > A() : i_(0) {} > explicit A(int i) : i_(i) {} > }; > > const int N = 5; > A a_list[N] = { A(-3), A(1), A(3), A(2), A(-4) }; > > typedef boost::function fn_t; > > // sorting a_list according to the elements' i_ member > std::stable_sort(boost::make_transform_iterator(a_list, fn_t(boost::bind(&A::i_, _1))), > boost::make_transform_iterator(a_list+N, fn_t(boost::bind(&A::i_, _1))), > std::less()); > stable_sort assumes that the sort keys are the same as the objects that it is moving around. In Christ, Steven Watanabe ------------------------------------------------------------------- 新浪空间——与朋友开心分享网络新生活！(http://space.sina.com.cn/ )

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about convert adjacency_matrix into common boost matrix
by Peng Wang 24 Dec '08

24 Dec '08

Hi, I am a newbie of boost. Could I ask one question that how to convert BGL adjacency_matrix object into common matrix (http://www.boost.org/doc/libs/1_37_0/libs/numeric/ublas/doc/matrix.htm)? I am sorry that if the question is too simple. I have looked around but did not find a answer. Thank you very much in advance. Sincerely yours, Wang

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[iterator] transform_iterator
by Max 24 Dec '08

24 Dec '08

Hello I just came across transform_iterator and found it a useful generic tool. But is it possible for it to go further to make the following code get compiled and run as expected? struct A { int i_; A() : i_(0) {} explicit A(int i) : i_(i) {} }; const int N = 5; A a_list[N] = { A(-3), A(1), A(3), A(2), A(-4) }; typedef boost::function<int(A)> fn_t; // sorting a_list according to the elements' i_ member std::stable_sort(boost::make_transform_iterator(a_list, fn_t(boost::bind(&A::i_, _1))), boost::make_transform_iterator(a_list+N, fn_t(boost::bind(&A::i_, _1))), std::less<int>()); Thanks B/Rgds Max ------------------------------------------------------------------- 新浪空间——与朋友开心分享网络新生活！(http://space.sina.com.cn/ )

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Re: [Boost-users] [boost] [shared_ptr] A smarter smart pointer proposal for dyn
by Max 24 Dec '08

24 Dec '08

Hello Dotchevski, Could you please elaborate? Thanks. B/Rgds Max ----- Original Message ----- From: Emil Dotchevski To: boost(a)lists.boost.org Subject: Re: [boost] [shared_ptr] A smarter smart pointer proposal for dynamic libraries Date: 2008-12-24 12:37:33 As far as I can tell, the only reason your reset() appears to work is that it is inlined in the executable. The compiler doesn't guarantee inlining, so in general it will crash anyway. The solution to this problem is to inject the DLL's lifetime into any shared_ptrs obtained from that DLL; that is, make the shared_ptr keep the DLL afloat. This can be done easily (and non-intrusively) using shared_ptr's aliasing constructor. Emil Dotchevski Reverge Studios, Inc. http://www.revergestudios.com/reblog/index.php?n=ReCode ------------------------------------------------------------------- 新浪空间——与朋友开心分享网络新生活！(http://space.sina.com.cn/ )

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boost::interprocess on FreeBSD 7
by Andy Wiese 24 Dec '08

24 Dec '08

Using boost::interprocess from boost_1_37_0 on FreeBSD 7.0, I get a segmentation fault in pthread_mutex_lock() from /lib/libthr.so. 3, in what appears to anything related to a ShmemAllocator. For example, when I run the example from http://www.boost.org/doc/libs/1_37_0/doc/html/interprocess/allocators_conta… I get the segfault at this line: //Initialize the STL-like allocator const ShmemAllocator alloc_inst (segment.get_segment_manager()); I stepped back to this simple test after encountering this segfault (always in pthread_mutex_lock) when trying to use almost any function of segment_manager from managed_mapped_file. This is from an mapped file boost::interprocess::map structure that works very well on darwin. Is there any hope to getting this to work on FreeBSD? ----------------------------------------------------------------------------------------------- FWIW, here is the complete text of the example: void test_ipc2() { using namespace boost::interprocess; shared_memory_object::remove("MySharedMemory"); try{ //A managed shared memory where we can construct objects //associated with a c-string managed_shared_memory segment(create_only, "MySharedMemory", //segment name 65536); //Alias an STL-like allocator of ints that allocates ints from the segment typedef allocator<int, managed_shared_memory::segment_manager> ShmemAllocator; //Alias a vector that uses the previous STL-like allocator typedef vector<int, ShmemAllocator> MyVector; int initVal[] = {0, 1, 2, 3, 4, 5, 6 }; const int *begVal = initVal; const int *endVal = initVal + sizeof(initVal)/sizeof(initVal[0]); //Initialize the STL-like allocator const ShmemAllocator alloc_inst (segment.get_segment_manager()); //Construct the vector in the shared memory segment with the STL- like allocator //from a range of iterators MyVector *myvector = segment.construct<MyVector> ("MyVector")/*object name*/ (begVal /*first ctor parameter*/, endVal /*second ctor parameter*/, alloc_inst /*third ctor parameter*/); BOOST_CHECK(myvector); //Use vector as your want std::sort(myvector->rbegin(), myvector->rend()); // . . . //When done, destroy and delete vector from the segment segment.destroy<MyVector>("MyVector"); } catch(...){ shared_memory_object::remove("MySharedMemory"); throw; } shared_memory_object::remove("MySharedMemory"); }

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shared_ptr downcast
by Jason Cipriani 24 Dec '08

24 Dec '08

If I have: class Base { }; class Derived : public Base { }; And a container, e.g.: std::vector<boost::shared_ptr<Base> > objs; How do I downcast to a shared_ptr<Derived>? E.g.: boost::shared_ptr<Derived> d = (boost::shared_ptr<Derived>)objs[0]; I have a function that takes a shared_ptr<Derived> and all I have is a shared_ptr<Base>. I don't mind static_cast behavior, although dynamic_cast behavior would be ideal. Thanks, Jason

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[Spirit] Building an expression parser with boost.spirit
by Max 24 Dec '08

24 Dec '08

Thank you! It's really a vault full of spirit examples from beginning tutorials to full-fledged applications! Best regards Max ----- Original Message ----- From: Joel de Guzman To: boost-users(a)lists.boost.org Subject: Re: [Boost-users] [Spirit] Building an expression parser with boost.spirit Date: 2008-12-24 11:07:20 Max wrote: > Thank you Hartmut. > > I've found some simple examples using Google and an > expression parser, exactly as what I described, which is > built on boost.spirit: > > http://idlebox.net/2007/stx-exparser/#subsec_grammar Also, see http://spirit.sourceforge.net/repository/applications/show_contents.php Spirit2 has extensive calculator examples from the simplest expression evaluator progressing incrementally to a full C-like compiler. Regards, -- Joel de Guzman http://www.boostpro.com http://spirit.sf.net ------------------------------------------------------------------- 新浪空间——与朋友开心分享网络新生活！(http://space.sina.com.cn/ )

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