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[ICL] interval_map::find returns only const iterator
by CarlosRoVe 27 Jan '13

27 Jan '13

Hi, I am using boost v.1.49.0 and I have a question about ICL. We are building a system that stores information associated with time intervals. For this we are using the interval_map container, and every element that we insert in the map contains a right_open interval as the key, and an instance of the structure that holds the information as the value. Some of the features of the system are: 1. Minimum interval length is one second. 2. We have seen that the default behavior for interval_map is aggregate on overlap, but in our case we enforce that overlapping time intervals are not allowed. To achieve this, every time we try to insert an element we perform a check if the time interval overlaps with any of the existing intervals in the map, and if so, we ignore the element. 3. We should be able to modify the data associated with a time interval. We have seen that the find method of the interval_map container returns only a const iterator, but we would like to have a version of find that returns a non-const iterator as well. We want to be able to search for an element whose time interval contains a certain timestamp, and change its content. With the given requirements, find should return one element at most. For us it would be handy if ICL could also provide a version of find that returns a non-const iterator, but maybe I this would break the philosophy behind the design of ICL. We would be glad to hear ideas suggesting what we could do, or alternatives ways of dealing with other problem. Thank you very much. -- View this message in context: http://boost.2283326.n4.nabble.com/ICL-interval-map-find-returns-only-const… Sent from the Boost - Users mailing list archive at Nabble.com.

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boost::asio async
by huvcbo 26 Jan '13

26 Jan '13

Hello, I have a problem I hope I can get some help with. I use boost http-server3, I have a number of tcp/ip-client started and connects to a server, every 15 seconds sending tcp/ip-client a keepalive message. When an HTTP client connects get tcp/ip-client from a container, and from the http message, a new message must be sent via the tcp/ip-client, when the reply is received how can I return it to the http-session? When i send the message to the tcp/ip-client the http-session goes out of scope. Both http-server and tcp/ip-client use async_write and read. Appriciate any help. /Christer

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[accumulators] accumulator "adapters"?
by Pete Bartlett 25 Jan '13

25 Jan '13

Dear all, The accumulators library is a very nice way to get a set of statistics for a stream of numbers, doubles, say. Now let’s suppose I’m receiving a stream of boost::optional<double>s – e.g. let’s suppose I’m receiving simulation results and some simulations fail. It would be neat if I could somehow write and “adaptor accumulator” that took this stream of optionals and then, if they are not empty, pass them to an underlying accumulator. In rough terms: template<typename UnderlyingAccumulator , typename Sample > struct accumulator_adaptor { template<typename Args> void operator()( Args const& args) { Sample const& s = args[sample]; if( s ) { m_underlying_accumulator( *s ) ; //doesn’t compile UnderlyingAccumulator expects an Args, not a Sample } } private: UnderlyingAccumulator m_underlying_accumulator; }; (we might also define another accumulator that just counts the number of “bad” samples. Then by adding an appropriate feature adaptor, one could write something like accumulator_set< boost::optional<double> , tag::accumulator_adaptor< mean > , tag::bad_samples_count > For the data 1.0,2.0,boost::optional<double>(),4.0 This would return a mean of 7/3 and a bad_samples_count of 1. Is it possible for me to implement such an adaptor that would work for an arbitrary underlying accumulator? Thanks for your interest, Pete

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Does Boost have polymorphic functors as named-operators?
by TONGARI 25 Jan '13

25 Jan '13

Hi all, Is there something like -- functional::identity, functional::plus (not std::plus<T>), functional::assign...etc -- in Boost? I know I can use Phoenix _1, _1 + _2, _1 = _2..., but I'd expect something more basic. Sometimes I just need something like that but not willing to have all the ET things... Maybe they're just provided within Phoenix or Proto? Thanks for any help.

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HTTP server3 example question
by huvcbo 25 Jan '13

25 Jan '13

Hi all, I have problem with HTTP Server3 example, in connection::handle_write i have a dedline_timer with a async_wait. but before the handle_timed execute the connection_ptr goes out of scope, why? Appriciate any help. Christer The boost HTTP Server 3 in file connection.cpp in server.hpp boost::shared_ptr<connection> connection_ptr; server.cpp void server::handle_accept(const boost::system::error_code& e) { if (!e) { new_connection_->start(); new_connection_.reset(new connection(io_service_)); acceptor_.async_accept(new_connection_->socket(), boost::bind(&server::handle_accept, this, boost::asio::placeholders::error)); } } in connection.cpp void connection::handle_write(const boost::system::error_code& e) { if (!e) { const boost::shared_ptr<boost::asio::deadline_timer> t(new boost::asio::deadline_timer(*io_service_, boost::posix_time::seconds(15))); } } void connection::handle_timed( const boost::system::error_code& ec, const boost::shared_ptr<boost::asio::deadline_timer> t) { syslog(LOG_INFO, "handle_timed: %s", ec.message().c_str()); }

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boost::bind/boost::function and fast delegates
by Littlefield, Tyler 24 Jan '13

24 Jan '13

hello all: We have a project we're working on that will be distributed, and I didn't want to have to set boost as a dependency if we're only using boost::bind and boost::function. Given this, I had a couple steps. First I thought I could possibly just copy out the code and modify it a bit, but it uses a ton of boost::preprocessor, so that'd require copying that out too. I'd rather not imbed half of boost in the project. My other solution (and one I really like) was to write my own delegates. I set to work on this and it's coming out good, but I have a couple questions. I know you can assign function pointers to boost::function objects, though I've always done it through bind. I'm curious how this works though: I have a normal function pointer set up and working right now, but how does boost::function take other pointers (say to static methods)? Also I'm curious what boost::bind generates. I'd like to create my own version since I love using it to pass in arbitrary values/using placeholders, but the boost::function has to be able to take a newly constructed function object and bind to that from what I understand. The new function object somehow has it's arguments stored on the object so that the () operator can just pass those in. Any help here would be appreciated. Thanks, -- Take care, Ty http://tds-solutions.net The aspen project: a barebones light-weight mud engine: http://code.google.com/p/aspenmud He that will not reason is a bigot; he that cannot reason is a fool; he that dares not reason is a slave.

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Re: [Boost-users] intrusive_ptr vs shared-ptr
by John M. Dlugosz 24 Jan '13

24 Jan '13

Gottlob Frege<gottlobfrege(a)gmail.com> wrote: > Yes, I was wondering if the magic call inside of smart_ptr's constructor, > that handles the enabled_shared_from_this, wouldn't be better as a free > function, like smart_pointer_being_created(), which gives you an extension > point to go look up whether the object already had a smart pointer. It > could default back to the enabled_shared_from_this trick if you don't > override it for your types, etc. > > Qt's smart pointer has extra tracking like this - typically only turned on > in debugging. The issue boils down to non-intrusiveness. I used a base class 'can_handle' for types I planned on using smart pointers on, much as you inherit from enable_shared_from_this but without the need for CRTP. The free function that looks up the 'lifetime object' for any given pointer (which may or may not already exist in the system) can be overloaded for different ways of doing it for different classes, and inheriting from that base allows it to match the intrusive form. Now as it turns out I never needed to make shared_ptr's to types that I did not define (or trivially derive from), so it never bothered me; but the intent was that a non-intrusive general solution would use a map or something. Only later did I figure out the catch: knowing when the map can be cleaned up of counts to deleted objects. Certainly it can be done: the logic in the smart pointer "I hit zero, free it" code can call another free function to report it; the deleter can capture the need to supplement the normal destructor with additional cleanup; etc. Certainly with the maturity of current compilers there is no reason not to support "lost and found" in an efficient manner. If non-intrusive, it only pays for it when you construct a smart pointer from a raw pointer (potential "find"), and for creating fresh objects a make_shared bypasses that step and knows that it does not exist already in the system anyway. Or, just as you have shared_from_this available now only if enabled, you can have lost-and-found available only if enabled using the intrusive mechanism. Basically, shared_from_this would always work whether it was "in the system" already or not, and constructing a shared_ptr from a raw ptr that has such a base class would call shared_from_this on it rather than new'ing up the counter object. Easy. Hmm, a non-standard shared_from_this mechanism that works this way could still interoperate with code that expects standard shared_ptr class to be used, if you call it that way yourself when you need to "find". Standard code never will, and constructing a shared_ptr the normal way still works as it always did. Now I have noticed that the implementations for shared_from_this interact with internals of weak_ptr. But a portable implementation doesn't have to. If I had time to write for magazines (and such magazines still existed) I'd write that up for an issue. —John

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(no subject)
by khaled hamidouche 24 Jan '13

24 Jan '13

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[1.53.0] Beta1 release available
by Marshall Clow 24 Jan '13

24 Jan '13

Boost release 1.53.0 beta 1 is now available from SourceForge. See https://sourceforge.net/projects/boost/files/boost/1.53.0.beta.1/ This release contains numerous enhancements and bug fixes for existing libraries. For details of what's in the release, see http://www.boost.org/users/history/version_1_53_0.html. Please download the beta, give it a try, and report any problems you encounter. Thank you, -- The Boost Release Team Beman Dawes, Eric Niebler, Rene Rivera, Daniel James, Vladimir Prus and Marshall Clow.

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[MultiIndex] question on replace() documentation
by John M. Dlugosz 24 Jan '13

24 Jan '13

“|replace| performs this substitution in such a manner that: … Iterator and reference validity are preserved.” I suppose "Iterator validity is preserved" means that no iterators are invalidated by this operation. Does that refer to the iterator passed as the first argument, too? That is, the iterator that referred to the replaced element now refers to the new element? And other indexes' iterators referring to the same element (e.g. project()) too? That might still be "valid" in the STL sense but might not continue to work if the position changed (e.g. it is now past the end of the range you are following). That's presuming the changed (but still "valid") iterator follows the new sort order rather than remembering the original order. Can someone clarify? My original reason for writing was to as what is meant by "reference validity is preserved"? Does that mean that the address of the items stored in the collection are not changed, and never move around as a result of this operation? —John

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