October 2008 - Boost - lists.boost.org

[MultiIndex] interface comments
by David Abrahams 05 Nov '08

05 Nov '08

Just reading through the docs for this very useful library and I had a few notes: 0. The term /typelist/ (italicized) is used in the tutorial without definition. Do you mean an MPL type sequence, or something else? 1. Seems like the tags functionality could take advantage of Boost.Parameter to provide a nicer interface and save some code. 2. The "shortcuts" save exactly 1 character. Each index of a multi_index_container uses its own iterator types, which are different from those of another indices. As is the rule with STL containers, these iterators are defined as nested types of the index: employee_set::nth_index<1>::type::iterator it= es.get<1>().find("Judy Smith"); <snip> Additionally, multi_index_containers provide shortcut definitions to the iterator types of their constituent indices: employee_set::nth_index_iterator<1>::type it= es.get<1>().find("Judy Smith"); There is a variation of the expression above for use with tags: employee_set::index_iterator<name>::type it= es.get<name>().find("Judy Smith"); // get<1> would also work Notice the column in which "it" appears in both versions. IMO these interfaces should be deprecated (i.e. not documented, and eventually removed) as they provide no readability advantage, hurt learnability, and complicate usage. Regards, -- Dave Abrahams BoostPro Computing http://www.boostpro.com

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[threadpool] new version v12
by k-oli＠gmx.de 04 Nov '08

04 Nov '08

Hello, the new version of Boost.Threadpool depends on Boost.Fiber. regards, Oliver

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[1.37.0][date-time] Breaking the log jam
by Beman Dawes 04 Nov '08

04 Nov '08

Andrey Semashev has pulled together a number of patches to address backed-up date-time tickets. He has tested them on Linux and Windows. The arrangement was that Jeff Garland would look them over, but Jeff just isn't finding the time to do that. I've taken a look at a few of the proposed fixes. Without knowing anything about date-time, these seem like problems that really should have been fixed some time ago.The proposed patches I looked at seemed fine. So I think it is important we break the log jam. Proposal: * We give Andrey write permission. * He starts moving these fixes into trunk right away. * Anyone who cares about data-time watch the commits carefully, and discuss any issues with Andrey. * Once Andrey is satisfied with trunk test results, he asks permission to merge to release. * Unless there has been undue delay or issues have come up, we will give permission for this release. * I'm willing to hold the release a few days; in aggregate this is an important set of overdue fixes to a major library so I'd like to see them go in this release. Comments? --Beman

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new libaray Boost.Fiber in vault
by k-oli＠gmx.de 03 Nov '08

03 Nov '08

Hello, I've added Boost.Fiber to the boost vault. The library implements lightweight threads of execution (context swapping; fibers on Windows). regards, Oliver

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[MultiIndex] "Compatible Sorting Criterion"
by David Abrahams 02 Nov '08

02 Nov '08

The docs mention that the definition is cumbersome. I think you could probably do much better with a formulation that relies on the concept of being partitioned with respect to a predicate function. See www.open-std.org/jtc1/sc22/wg21/docs/papers/2001/n1313.html and the wording changes (now in the standard) at: http://anubis.dkuug.dk/jtc1/sc22/wg21/docs/lwg-defects.html#270 -- Dave Abrahams BoostPro Computing http://www.boostpro.com

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Negative Cycle Detection Code
by Paul De La Musica 02 Nov '08

02 Nov '08

Hi, Is there any negative cycle detection code in the public domain? We would prefer BGL based code but LEDA is fine too. Thanks, Paul

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[type-traits] virtual function type trait check
by Chris 02 Nov '08

02 Nov '08

I was wondering if it were possible to make a is_virtual_function type trait check. Example: class B { public: virtual void complicatedFunction() { } }; class D : public B { public: void complicatedFnction() { static_assert(**check if D::complicatedFnction() is virtual **); // notice the misspelling. } };

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Style Guideline
by Robert Jones 31 Oct '08

31 Oct '08

Writing the kind of code that you see in the Boost libraries is something of a step change from the day-to-day production code that I write, and I suspect most of us write (Joel, Eric, Dave, Peter and others excepted of course! :-) ), and writing it, I find, is a rather different matter from reading it and broadly understanding it! So,....enable_if.... Is enable_if intended only to include or exclude complementary instantiations of different templates from the possible set, or also to control whether a particular instantiation is available at all? Say I have a class which I want to be able to instantiate only for vectors. Is it sensible to create an is_vector<> template and then use enable_if, or should I simply allow instantiation to fail when the code uses some aspect of vectors which is specific to vectors? Does the situation change if it is vectors or lists that are permissible? Or if it's anything with begin() & end() defined? Or am I making a complete hash of this, and ought to be thinking in a different paradigm? Thanks in advance. - Rob.

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[Timer] Inconsistent behaviour
by Jordans, R. 31 Oct '08

31 Oct '08

Hey all, I was looking at Boost.Timer and I noticed that it shows different results when it's used in a threaded program on Windows or Unix machines. A closer inspection revealed that it uses clock() to do it's timings. Digging a bit deeper I found that clock() is specified differently on Windows than it is in my Linux man-page. On windows it counts 'wall clock' time, basically what I'd expect from a class named timer but on Linux it counts CPU time. Thus it will give the result for completely different concepts of time elapsed depending on my system. Two questions; 1) is there a good way to solve this, 2) if not, could it at least be noted in the documentation. Thanks, Roel

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first Visual Studio 2010 CTP is out, c++0x
by Cory Nelson 31 Oct '08

31 Oct '08

In case anyone missed it, a VS10 CTP is out with partial 0x support (lambda, rvalue, static assert, and "auto"), better intellisense, and a modern c++ parallel library. http://www.microsoft.com/downloads/details.aspx?familyid=922b4655-93d0-4476… -- Cory Nelson

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