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[Units] How to use units from different systems
by Juan José Icaza 23 Dec '08

23 Dec '08

I am trying to use the boost::units library for the first time. I'm able to use the SI system. However, I would like to use units from different systems. Particularly, I would like to be able to write: quantity<si::length> L = 3.0 * us::inch + 0.50 * si::meter; The library comes with a us::inch_base_unit. But I don't know how to create a us::inch unit. Any help is appreciated. Juan José

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Graph-Based Threaded Algorithms
by James C. Sutherland 23 Dec '08

23 Dec '08

I am looking for some guidance from some of the graph and thread experts out there. I have a graph that I want to execute a breadth-first search (BFS) on. When each node is visited, it spawns a thread to execute some work. I must not execute a child node before the parent execution is completed, but I also want to maximize concurrency. In other words, I don't want to "serialize" the BFS to force proper execution ordering. Are there any ideas of how to accomplish this efficiently? James --- James C. Sutherland Assistant Professor, Chemical Engineering The University of Utah 50 S. Central Campus Dr, 3290 MEB Salt Lake City, UT 84112-9203 (801) 585-1246 http://www.che.utah.edu/~sutherland

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Determine base class member function pointer for member function pointer of derived class.
by Siegfried Kettlitz 23 Dec '08

23 Dec '08

Hello, is there an automatic way to determine the base class member function pointer &base::fn from the derived member function pointer &derived::fn? Or do you know that there is no way to do this with current c++? It should work like this: class base { public: virtual void fn( void ); }; class derived : public base { public: void fn( void ); } main() { base_pointer = get_base_pointer( &derived::fn ); } Thanks, Siegfried

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Re: [Boost-users] [STL] Is there a std::abs<>() function? (Max)
by Max 23 Dec '08

23 Dec '08

Hello Scott I'm not sure what you mean by ADL? Thanks for reply. Best regards Max ----- Original Message ----- From: Scott McMurray To: boost-users(a)lists.boost.org Subject: Re: [Boost-users] [STL] Is there a std::abs<>() function? (Max) Date: 2008-12-23 12:42:48 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 ). ~ Scott ------------------------------------------------------------------- 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] [STL] Is there a std::abs<>() function? (Max)
by Max 23 Dec '08

23 Dec '08

hello Philip, Thanks for your reply. What I need is a template version of abs, not the int abs(int) function, to make use of it genericly. B/Rgds Max ----- Original Message ----- From: Philip Ogunbona To: boost-users(a)lists.boost.org Subject: [Boost-users] [STL] Is there a std::abs<>() function? (Max) Date: 2008-12-22 23:45:52 Max, Using STL does not prevent access to abs(), fabs() and labs(). You just need to #include . Is that what you want? Philip ------------------------------------------------------------------- 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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[Spirit] Building an expression parser with boost.spirit or any other
by Max 23 Dec '08

23 Dec '08

Hello all, There are several parsing tool libs in boost, say spirit and wave, pheonix, etc. But I am just not quite clear of the relation between each of them. I've skimmed through some of the documentation some time ago, but it seems to be too tough to me till now. My question is, giving the huge power of these libs, is it simple to construct an traditional expression parser which accepts formulea like: 1+2/3 sin(0.34)/power(tan(.4),3) and so on Or, preferably, is there already a sample program like this anywhere? Thanks for any hints. 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] [bind] Need Help - Function Composition
by Max 23 Dec '08

23 Dec '08

Thank you, Watanabe. B/Rgds Max ----- Original Message ----- From: Steven Watanabe To: boost-users(a)lists.boost.org Subject: Re: [Boost-users] [bind] Need Help - Function Composition Date: 2008-12-21 10:50:22 AMDG loadcom wrote: > I'm not sure if what you mean is that in your use case: > boost::function f = make_less_by_func(boost::bind(...)); > the temporarily constructed bind obj will go out of its lifetime before > we use it via a refence to it? Yes. the temporary is destroyed as soon as the boost::function constructor runs. f is then left with a reference to an object that has been destroyed. > But if I cannot declare > > const F& func_; > > instead of > > F func_; > > then why bother using another ref lib? > You can use a reference in some cases. Using Boost.Ref forces the caller to be explicit about whether to use a reference so presumably the user knows that it is safe. > or, in other words, is there a way to save this 'unneeded' copy > construction and allow us to use > > make_less_by_func(boost::bind(...)) > ? > There is no way to avoid the copy while maintaining this interface. However, it is quite likely that the compiler can optimize away the copy when you are only using Boost.Bind with built in types. > btw, I'm not using ref lib frequently, but should boost::unwrap_ref > be boost::unwrap_reference? > No. boost::unwrap_reference is a metafunction. 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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[STL] Is there a std::abs<>() function?
by Max 23 Dec '08

23 Dec '08

Hello, It's strange to me that there seems not to be a std::abs<>() function in STL, with it I can write code like this: double d = std::abs(-1.0); int i = std::abs(-1); Does anybody else have the same feeling? Being uncomfortable with the abcence of it, I've wrote my own version in my namespace: #include <boost/utility/value_init.hpp> // my abs function // it works not only for POD types, but also for // user types that are default constructible and // support operator<() and unary operator-() template<class T> T abs(const T & x) { static boost::value_initialized<T> zero; return (x < zero? -x : x); } Thanks for any information. Best regards 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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[STL] Is there a std::abs<>() function? (Max)
by Philip Ogunbona 22 Dec '08

22 Dec '08

Max, Using STL does not prevent access to abs(), fabs() and labs(). You just need to #include <cstdlib>. Is that what you want? Philip

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Access to BGL errata?
by Roger House 22 Dec '08

22 Dec '08

When I click on BGL Book Errata at the link below, I'm asked for a username and password. The name and password I use as a Boost User Subscriber don't seem to work. What is the magic incantation needed to access the errata? Roger House Software Developer http://www.boost.org/doc/libs/1_37_0/libs/graph/doc/table_of_contents.html

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