February 2004 - Boost-users - lists.preview.boost.org

[BGL] Removing vertices and internal properties
by Frédéric Mayot 09 Feb '04

09 Feb '04

Hi, I have a graph in the form of an adjacency_list with an internal property. I'm using vecS for both vertices and edges (and I don't want to use listS). When I remove a vertex with remove_vertex(), it seems that my property map is invalidated. Can I remove the property (from the map) which corresponds to the deleted vertex ? Is there any solution ? Thanks. Fred

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Dynamic Multi Array Library
by RGProlog＠aol.com 09 Feb '04

09 Feb '04

Is anyone interested in dynamic_multi_array template library that offers user intuitive convenience of use as well as capacity to hone in upon any specific subset of a multi-dimensional array? As an example of usage, a dynamic_multi_array object can be constructed and then resized and then reshaped like this: size_t arrayShape = { 3, 7, 15}; dynamic_multi_array<double, 3> A(arrayShape); boost::array<size_t, 3> anotherArrayShape = {{ 5, 4, 22}}; A.resize(anotherArrayShape); boost::array<size_t, 5> yetAnotherArrayShape = {{ 440, 1, 1, 0, 0}} ; A.reshape(yetAnotherArrayShape); size_t stillAnotherArrayShape[4] = { 22, 10, 2, 11}; A.reshape(stillAnotherArrayShape); The library’s design owes a lot to Andrei Alexandrescu’s ideas. It is based on the data_table helper class template defined as follows: template<typename X> class data_table { … protected: std::vector<X> data_table_ ;}; template<> <value_type> class data_table { … protected: value_type* data_table_ ;}; Then, a sequence of the table class instantiation types is recursively defined and then given a name that is shared in different dimensional contexts as follows: typedef data_table<value_type> data_table_01; ……………………………………………. typedef data_table< data_table_49 > data_table_50 ; class Int2Type<int> { typedef data_table_01 data_table; } …………………………………………… class Int2Type<> <50> { typedef data_table_50 data_table; } Being a recursive template class, the data_table is implemented in a concise code that is mostly about stating a few recursive rules and implementing some access operators and is totally dimension independent. This is the central feature of the design since the user level wrapper class template by virtue of exporting a dimension appropriate data_table instantiation that uses its shared name template <T, size_t i, Allocator> class dynamic_multi_array { ………………………………………. typedef …. class Int2Type <i>::data_table; } is also implemented in a way that hides all the implementation details, is concise and dimension independent, thus providing user with a great deal of flexibility, syntax safety, and, in case of a new user, a flat learning curve. This is a std::vector based design. The dynamic_multi_array template class, the library’s main component, extends, where appropriate, std::vector capacities, replicates its exception safety guarantees and has std::vector as its back end storage device. The library’s code, documentation that includes a short tutorial and a few key tests and will be posted in Dynamic Multi Array Folder on boost Files once the issue of available space will be resolved.

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(no subject)
by RGProlog＠aol.com 09 Feb '04

09 Feb '04

Is anyone interested in dynamic_multi_array template library that offers user intuitive convenience of use as well as capacity to hone in upon any specific subset of a multi-dimensional array? As an example of usage, a dynamic_multi_array object can be constructed and then resized and then reshaped like this: size_t arrayShape = { 3, 7, 15}; dynamic_multi_array<double, 3> A(arrayShape); boost::array<size_t, 3> anotherArrayShape = {{ 5, 4, 22}}; A.resize(anotherArrayShape); boost::array<size_t, 5> yetAnotherArrayShape = {{ 440, 1, 1, 0, 0}} ; A.reshape(yetAnotherArrayShape); size_t stillAnotherArrayShape[4] = { 22, 10, 2, 11}; A.reshape(stillAnotherArrayShape); The library’s design owes a lot to Andrei Alexandrescu’s ideas. It is based on the data_table helper class template defined as follows: template<typename X> class data_table { … protected: std::vector<X> data_table_ ;}; template<> <value_type> class data_table { … protected: value_type* data_table_ ;}; Then, a sequence of the table class instantiation types is recursively defined and then given a name that is shared in different dimensional contexts as follows: typedef data_table<value_type> data_table_01; ……………………………………………. typedef data_table< data_table_49 > data_table_50 ; class Int2Type<int> { typedef data_table_01 data_table; } …………………………………………… class Int2Type<> <50> { typedef data_table_50 data_table; } Being a recursive template class, the data_table is implemented in a concise code that is mostly about stating a few recursive rules and implementing some access operators and is totally dimension independent. This is the central feature of the design since the user level wrapper class template by virtue of exporting a dimension appropriate data_table instantiation that uses its shared name template <T, size_t i, Allocator> class dynamic_multi_array { ………………………………………. typedef …. class Int2Type <i>::data_table; } is also implemented in a way that hides all the implementation details, is concise and dimension independent, thus providing user with a great deal of flexibility, syntax safety, and, in case of a new user, a flat learning curve. This is a std::vector based design. The dynamic_multi_array template class, the library’s main component, extends, where appropriate, std::vector capacities, replicates its exception safety guarantees and has std::vector as its back end storage device. The library’s code, documentation that includes a short tutorial and a few key tests and will be posted in Dynamic Multi Array Folder on boost Files once the issue of available space will be resolved. P.S. The space issue is that I freed the space I previously occupied on boost Files and still cannot post the message. Need help here.

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RE: [Boost-users] configuring boost on MS Visual Studio 6 where the installation drive isn't C:
by Dernoncourt, Wayne CTR NAVAIR 3184, ,10 09 Feb '04

09 Feb '04

Thanks much. I think the folks here have sent a message (I leave here a little after 1:30 on Friday and discussion sometimes takes a while) to the other SDK developers asking if they could put their SDK in a namespace and do this the "right" way instead of this round-about method. But yes this could work as well. Thanks much. -----Original Message----- From: boost-users-bounces(a)lists.boost.org [mailto:boost-users-bounces@lists.boost.org]On Behalf Of Administrator Sent: Friday, February 06, 2004 12:57 To: 'Boost Users mailing list' Subject: RE: [Boost-users] configuring boost on MS Visual Studio 6 where the installation drive isn't C: Wayne, There might still be conflicts if the compiler can't place everything into it's proper namespace. In addition, some sdk's force everything into std namespace or into the global namespace. If you use "using namespace boost;", you're basically doing the same thing. There are a couple of options that could be used separately. 1. One is to not use "using namespace". Preface everything used from there with boost:: or std::. More typing, less pain, less chance for conflict. 2. The second is wrap the offending sdk in it's own namespace. Here is what I have come up with. I have three files here. c.h is the original function. b.h wraps it in it's own namespace, and main.cpp can only use it with the new namespace. Simple example, but hopefully it illustrates what I'm trying to get across. -------------------------------------------------- c.h ------------------------------------------------- #ifndef _C_H #define _C_H inline int garbage_method() { return 0; } #endif // -------------------------------------------------- b.h -------------------------------------------------- #ifndef _B_H #define _B_H namespace garbage_namespace { #include "c.h" } #endif // -------------------------------------------------- main.cpp -------------------------------------------------- #include "b.h" int main() { return garbage_namespace::garbage_method(); }

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suspend/cancel thread
by janardhan.guptha＠efi.com 09 Feb '04

09 Feb '04

Hi, i working on an application using boost::thread. The application cretaes a thread, then put in wait state. Based on the user input i want the thread eitjer to move it to run state or cancel the thread. As i am newbie to boost thread, i couldn't find any documentation or working example that satisfies my requiremnt. So someone can help me out?? Rgds, Janardhan

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std::map problem.
by Joshua Little 08 Feb '04

08 Feb '04

I'm working on making a factory class but have run into a problem. I think I'm trying to get the shared pointer out the wrong way. std::map<std::string, boost::shared_ptr<Logger> > LoggerFactory::loggers; boost::shared_ptr<Logger> LoggerFactory::getInstance(std::string& logger) { boost::shared_ptr<Logger> TheLogger; LoggerMap::iterator i = loggers.find(logger); if (!(*i).second.get()) { TheLogger.reset(new Logger()); loggers[logger] = TheLogger; } else { TheLogger = (*i).second; } return TheLogger; } I thought that the TheLogger = (*i).second line was the correct way to get any logger within the map but when I run it I get this segfault: Program received signal SIGSEGV, Segmentation fault. LoggerFactory::getInstance(std::string&) (logger=@0x22ff58) at e:/boost-1.30.2/boost/detail/shared_count.hpp:123 123 if(use_count_ == 0 && weak_count_ != 0) boost::throw_exception(boost::bad_weak_ptr()); if I comment out the 'TheLogger = (*i).second;' line everything seems to fine. Any ideas? Joshua.

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Help with shared_ptrs please
by Steve Folly 08 Feb '04

08 Feb '04

Hi, I'd like some help trying to crack a problem I've got. Now, I am using shared pointers at the moment, and that might be part of my problem, or it might not, but I'll describe the situation and you can tell to go elsewhere if you like! :) Part of my application involves scripting - allowing the user to write file based scripts to execute within the context of an application. I've designed it so it also gives the ability for the application writer to create some 'scripts' by creating classes directly in the C++ code. The script has the ability to run in the main thread of the app, but some statements could potentially block, so each statement is run from a 'timer' event which gets scheduled immediately. Those that block wait for an event and continue on that event. This part is working well. The statements are classes constructed in a hierarchical manner with things like a block class (a statement itself) which has a list of statements in it, an if statement class - which has an expression evaluator, a statement for the 'then' part, and an optional statement for the 'else' part. You get the idea? After looking at boost::lambda I thought it would be nice if I could construct my script similar to how lambda does these sorts of control statements - the if_, switch_, for_ constructs. The idea I have is like: expression exp = ... If_statement s1 = if_( expr)->then_( s2 )->else_( s3 ); while_statement ws = while_( expr ).do_( s1 ); One of the things I decided early on was to use shared_ptrs. The while_ and if_ constructs are functions returning a shared pointer to the real if statement object. Now my problem: given the example above. The do_ method of a while_statement takes a shared pointer to a statement so I don't have to worry about deallocation. Constructing the if_ statement on it's own is no problem, but if I was to construct one directly within the do_ part of the while statement it wont compile: while_( expr ).do_( if_(expr)->then_(s2)->else_(s3) ); The problem is to be able to chain then_ and else_ together, I have to return a plain pointer because the if_ statement itself doesn't know about it's shared pointer. So now, the compiler complains that can't implicitly convert a plain if_statement pointer into a shared pointer. And even if it could, I don't have the original shared pointer to hand. Now, I hope you're all still listening at the back! :) My first thought was to somehow get the object to look after the shared pointer, but surely if the object has a reference to itself, the ref count of the shared pointer could never reach zero? As I said right at the beginning, I think is a problem I have with shared pointers, whether it be a misunderstanding about them or maybe I'm using them the wrong way? I could always go for scrapping the shared pointers all together, and make the classes responsible for their own (de)allocation, but I was rather hoping to avoid that. Any tips and suggestions on ways forward will be much appreciated. (Even if to say - "ha! it'll never work", or "try a another newsgroup"! :) TIA. -- Regards, Steve.

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PreProcessor Library and Class Constructors
by Paul Grenyer 07 Feb '04

07 Feb '04

Hi All I fear I may be trying to get a square peg in a round hole, but here goes anyway... I'm trying to use the boost PreProcessor library to generate constructors with varying numbers of parameters. I've tried the following: #include <boost/preprocessor/arithmetic/inc.hpp> #include <boost/preprocessor/punctuation/comma_if.hpp> #include <boost/preprocessor/repetition.hpp> #ifndef MAX_CONCRETE_CONSTRUCTOR_PARAMS #define MAX_CONCRETE_CONSTRUCTOR_PARAMS 3 #endif #define CONCRETE_CONSTRUCTOR(Z, N, _) \ template<class R BOOST_PP_COMMA_IF(N) BOOST_PP_ENUM_PARAMS(N, class A)> \ explicit Concrete( BOOST_PP_ENUM_PARAMS(N, A) ) \ { } class Concrete { public: BOOST_PP_REPEAT(BOOST_PP_INC(MAX_CONCRETE_CONSTRUCTOR_PARAMS), CONCRETE_CONSTRUCTOR, _) }; int main() { Concrete a( 1, 2 ); return EXIT_SUCCESS; } But this gives me the following error: error C2660: 'Concrete::Concrete' : function does not take 2 arguments I have feeling I'm doing something very wrong or that can't be done. Regards Paul Paul Grenyer Email: paul(a)paulgrenyer.co.uk Web: http://www.paulgrenyer.co.uk Have you met Aeryn: http://www.paulgrenyer.co.uk/aeryn/? Version 0.3.0 beta now ready for download

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RE: [Boost-users] How to export arrays from C(++) to python using boost
by Shukla, Nitin (Export) 06 Feb '04

06 Feb '04

Hi, I working on an application where an array of ints and floats are to exported from C++ to Python using boost::python. As I am newbie to boost python, I couldn't find any documentation or working example that satisfies the above requirement. Can someone help me out?? Nitin. -----Original Message----- From: Shukla, Nitin (Export) [mailto:nitin.shukla@pw.utc.com] Sent: Thursday, February 05, 2004 3:19 PM To: 'boost-users(a)lists.boost.org' Subject: [Boost-users] How to export arrays from C(++) to python using boost I want to export an array of int and floats from C(++) to python using Boost but don't know how? Can anyone help me out? Is there any tutorials specifically on C(++)/Python interfacing using the Boost tool? I also want to export the BOOL type of C(++) to Python. How can I do that? --Nitin _______________________________________________ Boost-users mailing list Boost-users(a)lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users

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RE: [Boost-users] configuring boost on MS Visual Studio 6 where t he installation drive isn't C:
by Administrator 06 Feb '04

06 Feb '04

Wayne, There might still be conflicts if the compiler can't place everything into it's proper namespace. In addition, some sdk's force everything into std namespace or into the global namespace. If you use "using namespace boost;", you're basically doing the same thing. There are a couple of options that could be used separately. 1. One is to not use "using namespace". Preface everything used from there with boost:: or std::. More typing, less pain, less chance for conflict. 2. The second is wrap the offending sdk in it's own namespace. Here is what I have come up with. I have three files here. c.h is the original function. b.h wraps it in it's own namespace, and main.cpp can only use it with the new namespace. Simple example, but hopefully it illustrates what I'm trying to get across. -------------------------------------------------- c.h ------------------------------------------------- #ifndef _C_H #define _C_H inline int garbage_method() { return 0; } #endif // -------------------------------------------------- b.h -------------------------------------------------- #ifndef _B_H #define _B_H namespace garbage_namespace { #include "c.h" } #endif // -------------------------------------------------- main.cpp -------------------------------------------------- #include "b.h" int main() { return garbage_namespace::garbage_method(); } -----Original Message----- From: Dernoncourt, Wayne CTR NAVAIR 3184, ,10 [mailto:wayne.dernoncourt@navy.mil] Sent: Friday, February 06, 2004 5:43 AM To: Boost Users mailing list Subject: RE: [Boost-users] configuring boost on MS Visual Studio 6 where the installation drive isn't C: Well that worked much better as far as it went (747 updated files out of 747 targets wth no skipped files and no failures). The version of the bjam binary was a little larger (~5k) than the one I compiled<scratches head>, but using this produced no errors. Unfortunately we still have at least a few problems. As I described originally we are using a highly specialized third party SDK. Part of this SDK redefines reverse_iterator (as well as min & max) evidently the MS Visual C++ reverse iterator is broken in some way. From a cursory examination of the two implementations, it appears that both the two are very similiar in functionality if not implementation. The issue with min/max could be eliminated by commenting out line 59 of boost/config/stllib/dinkumware.hpp (line defines BOOST_NO_STD_MIN_MAX). There doesn't appear to be a similiar line for the reverse iterator. One of the issues appears to be that this third party SDK doesn't seem to use namespaces for the SDK. From my limited understanding, for namespaces to be used effectively, the different libraries/SDK's would need to be in their own namespaces. If Boost had theirs and the third party used the global namespaces, there could still be conflicts. Is my understanding correct?

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