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Re: [boost] [Iterators] Iterators and higher-order programming
by Thomas Jordan 07 May '10

07 May '10

Mathias Gaunard wrote: -------------------------------------------------------------------- Message: 2 Date: Sun, 25 Apr 2010 12:33:51 +0100 From: Mathias Gaunard <mathias.gaunard(a)ens-lyon.org> To: boost(a)lists.boost.org Subject: Re: [boost] [Iterators] Iterators and higher-order programming Message-ID: <hr19av$sgp$1(a)dough.gmane.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Thomas Jordan a ?crit : > Hi, > One of the interesting things about the iterators library, it seems to me, is the additional support it gives for higher-order, > functional-style programming. For example, you can use the transform and filter iterators to produce a simple 'Comprehension' object > which permits list-comprehension type of syntax to be used, instead of conventional loops You might want to look at the range library then, which has been recently modified to add support for things like: some_range | transformed(f) | filtered(p) ----------------------------------------- Thanks/merci, Mathias (and apologies for my late reply), I am now looking at 1.43.0 Boost::Range! T.

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bjam's use of O_NONBLOCK in execunix.c
by Dan Gohman 06 May '10

06 May '10

Hello, Why does bjam on "unix" platforms set the O_NONBLOCK flag when creating standard output and error pipes from the child process to the parent process? https://svn.boost.org/trac/boost/browser/trunk/tools/jam/src/execunix.c#L189 This was introduced in change r38009: https://svn.boost.org/trac/boost/changeset/38009 The parent process uses select(2) to block and wait for output from children, so it doesn't appear to need non-blocking file descriptors. Child processes are unrelated programs, and it seems mistaken to assume that they will want their stdout and stderr to be non-blocking. A project that I'm involved in recently had to add code to handle EAGAIN from a write(2) call by spinning until it succeeds, and it seems to be fairly common practice. It would seem to be better if the parent would just leave the file descriptors in blocking mode. Thanks, Dan

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[fusion] BOOST_FUSION_ADAPT_CLASS* not documented
by Michael Caisse 06 May '10

06 May '10

I may be able to submit a patch after boostcon but I thought I would first check to see if this is just an issues with the latest docs not being checked in. I just verified the trunk is missing docs about the class adaption macros. regards - michael -- ---------------------------------- Michael Caisse Object Modeling Designs www.objectmodelingdesigns.com

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[paired ptr] Proposing a new smart pointer object for managing bidirectional relationships between objects
by Dan Walters 06 May '10

06 May '10

Dear all, I have been working on a proposal for a useful utility for managing non hierarchal, bi-directional relationships between objects and as a useful tool in object composition. This utility is in the form of a type of templated smart pointer that can connect to one single other pointer and manage the relationship between the two pointers. This paired_ptr object is intended for use as a member of (or at least contained within) a user defined object and is conceptualized from the needs of object composition. Prototype source code, a usage example and brief documentation is available here: http://www.boostpro.com/vault/index.php?action=downloadfile&filename=paired… Doumentation only is available here: (this is a google doc and is continually being updated) http://docs.google.com/View?id=dc33pnfx_442s22z7d6 I am posting here in the hope it will generate suitable interest that it may be worth developing as a full library for submission. Best wishes, Dan

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Re: [boost] [MSM] passing constructor arguments to frontend asreference.
by Christophe Henry 06 May '10

06 May '10

> Hi, All > > we might found a problem when passing constructor arguments to the > front end in case constructor arguments are passed by reference. > In that case you do not pass the argument as reference in the first > place rather copy construct a new object and pass that object as > reference to the front end. > We looked into the preprocessor code which we believe verified our assumption: > > (code snippet only contains the first part with one constructor argument!) > > template < class ARG0> > state_machine<Derived,HistoryPolicy,CompilePolicy >( ARG0 t0 ) > :Derived( t0) ,m_events_queue() ,m_deferred_events_queue() > ,m_history() ,m_event_processing(false) ,m_is_included(false) > ,m_visitors() ,m_substate_list() { ::boost::mpl::for_each< > seq_initial_states, ::boost::msm::wrap<mpl::placeholders::_1> > > (init_states(m_states)); m_history.set_initial_states(m_states); > fill_states(this); } > > > In our case, if we want to pass a reference, ARG0 has to be declared as follows: > template < class ARG0> > state_machine<Derived,HistoryPolicy,CompilePolicy >( ARG0& t0 ) > :Derived( t0) .... > > The "Derived" class looks like as follows: > class "Derived" > { > public: > Derived(SomeClass& cl_) {} > } > > Do you have any idea how to solve this? > > Thanks in advance. > > Richie & Michi Hi, It's a classical issue with template arguments and something I definitely should have written in the doc. To pass arguments by reference, you need to use boost::ref (or boost::cref for const references), for example: // The "Derived" class looks like as follows: class Derived : public msm::front::state_machine_def<Derived> { public: Derived(SomeClass& cl_) {} ... } typedef msm::back::state_machine<Derived> MyFsm; SomeClass stuff; ... MyFsm fsm (boost::ref(stuff)); Thanks for pointing this out, I will update the doc. Note: I fly tomorrow to the BoostCon, so I might be a bit less responsive (jetlagged) the first few days. HTH, Christophe

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[1.43.0] Release Candidate available
by Beman Dawes 06 May '10

06 May '10

The 1.43.0 release candidate files are available at http://boost.cowic.de/rc/ Before these get pushed out to SourceForge, we like to get verification that they download and build OK. So please download one of these for your favorite platform, try a build, and report success or failure here. Thanks, --Beman

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[1.43.0] Release notice
by Beman Dawes 06 May '10

06 May '10

Release 1.43.0 of the Boost C++ Libraries is now available. These open-source libraries work well with the C++ Standard Library, and are usable across a broad spectrum of applications. The Boost license encourages both commercial and non-commercial use. This release contains two new libraries (functional/factory, functional/forward), a major range library upgrade, plus numerous enhancements and bug fixes for other libraries. For details, including download links, see http://www.boost.org/users/news/version_1_43_0 The release can also be downloaded directly from SourceForge. See http://sourceforge.net/projects/boost/files/ To install this release on your system, see http://www.boost.org/doc/libs/1_43_0/more/getting_started/index.html Thanks to all who contributed, --The Boost release team

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[MSM] passing constructor arguments to frontend as reference.
by Richard Szabo 06 May '10

06 May '10

Hi, All we might found a problem when passing constructor arguments to the front end in case constructor arguments are passed by reference. In that case you do not pass the argument as reference in the first place rather copy construct a new object and pass that object as reference to the front end. We looked into the preprocessor code which we believe verified our assumption: (code snippet only contains the first part with one constructor argument!) template < class ARG0> state_machine<Derived,HistoryPolicy,CompilePolicy >( ARG0 t0 ) :Derived( t0) ,m_events_queue() ,m_deferred_events_queue() ,m_history() ,m_event_processing(false) ,m_is_included(false) ,m_visitors() ,m_substate_list() { ::boost::mpl::for_each< seq_initial_states, ::boost::msm::wrap<mpl::placeholders::_1> > (init_states(m_states)); m_history.set_initial_states(m_states); fill_states(this); } In our case, if we want to pass a reference, ARG0 has to be declared as follows: template < class ARG0> state_machine<Derived,HistoryPolicy,CompilePolicy >( ARG0& t0 ) :Derived( t0) .... The "Derived" class looks like as follows: class "Derived" { public: Derived(SomeClass& cl_) {} } Do you have any idea how to solve this? Thanks in advance. Richie & Michi

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Web site problems
by Beman Dawes 06 May '10

06 May '10

In a private email, Chris Ahlstrom reported: >On quite a few pages, when I enter the URL, a blank page comes up. > >Here's one example: > > http://www.boost.org/doc/tools/build/index.html It is actually weirder than that. The URL should be: http://www.boost.org/tools/build/index.html which should forward to: http://www.boost.org/doc/tools/build/v2/index.html but instead http://www.boost.org/doc/tools/build/index.html appears, and as a blank page. Any ideas? --Beman

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1.43.0 range_ex
by Neal Becker 06 May '10

06 May '10

Before 1.43.0, range_ex had boost::make_reversed_range. In 1.43.0, it seems to have been renamed to boost::adaptors::reverse. This is unfortunate, as there is also a boost::reverse function that means something different.

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