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ublas identity_matrix problem
by Heiko Bauke 08 Sep '04

08 Sep '04

Dear all, I discovered a problem in ublas identity_matrix class. I am doing linear algebra in finite fields. So my matrices contain no floats nor doubles. Instead I use some class that behaves like a number but does arithmetic in a finite field. Class instances are contructable by int, but _not_ default constructable by int. I don't want to have this. In matrix.hpp one finds the lines template<class T> typename identity_matrix<T>::value_type identity_matrix<T>::zero_=0; template<class T> typename identity_matrix<T>::value_type identity_matrix<T>::one_=1; These lines are problematic and the reason why my number class works not with the identity_matrix class. I think these lines should by changed into template<class T> typename identity_matrix<T>::value_type identity_matrix<T>::zero_=T(0); template<class T> typename identity_matrix<T>::value_type identity_matrix<T>::one_=T(1); to make the ublas code more general. with regards Heiko -- -- Gute Sitten haben für die Gesellschaft mehr Wert als alle -- Berechnungen Newtons. (Friedrich II., der Große, 1712-1786) -- Supercomputing in Magdeburg @ http://tina.nat.uni-magdeburg.de -- Heiko Bauke @ http://www.uni-magdeburg.de/bauke

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How to remove custom property map from graph dynamically ?
by Raj 08 Sep '04

08 Sep '04

Hi, I have an adjacency list graph with three custom property maps attached. At some point during the run of the program, I would like to remove two of those maps from the graph. Is it possible ? How can I do it ? Thanks in advance Raja

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RE: [Boost-users] Re: statically linking to Boost.Threads with msvc7
by Simmons, Aaron 08 Sep '04

08 Sep '04

> In Boost release 1.31, the Boost.Threads library doesn't support static > linking. This limitation will be removed in the next release (coming > soon) for: > > a) anyone using the pthreads implementation of Boost.Threads > b) anyone using Visual C++ on Win32 > > Hopefully it will be removed for other Win32 compilers in the future. How was the TSS problem solved for win32-threads? What's the ETA for the next version? Thanks, aaron

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macro m4 for boost
by Thomas Lemaire 08 Sep '04

08 Sep '04

Hi boost-users, I am looking for a macro m4 (used by autoconf) that automatically detects boost installation directory. Has anybody got it ? thomas

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dynamically created program options
by Rodolfo Schulz de Lima 08 Sep '04

08 Sep '04

Hi, I wonder if it's possible to handle dynamically created program options with boost::program_options. For instance: I have a config file that specifies configure options for dynamic loaded modules in my project. So the cfg file would be: [module.foo1] module_file = foo.so listen_port = 564 enabled = true [module.foo2] module_file = foo.so listen_port = 565 enabled = false [module.bar1] module_file = bar.so listen_port = 145 enabled = true As can be seen, foo1, foo2 and bar1 names are defined by the user in the configure file, and the program doesn't know about them before parsing the configuration. But if we parse that (somehow), an exception saying that the option "module.foo1.module_file" is invalid will be thrown. Can I manage the options_description "on the fly"? Another less complicated situation would be something like this: modules = foo1 foo2 bar1 [module.foo1] . . . [module.foo2] . . . [module.bar1] . . . So when parsing the "modules" option, we would know the new options name and it would be a matter of appending more option descriptions to the object. Regards, rod

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Min-Cut o Max-Flow in a graph?
by Daniele Carlucci 08 Sep '04

08 Sep '04

Hi, How can I find the min-cut, or the max-flow in a graph with all the costs of edges equal one? Thanks Daniele

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Comiling Boost with VC++.net
by Andreas Kempf 07 Sep '04

07 Sep '04

My IDE for C++ is VC++.net I heard that it is impossible to compile Boost with its compiler. I replaced the compiler with the VC++.net 2003 Toolkit Compiler, but it still doesn't work. Can anyone help me compiling with the VC++.net 2003 Toolkit?

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RE: [Boost-users] signal slot flexibility
by Frank Maddin 07 Sep '04

07 Sep '04

Ahh, so now I'm able to do such things as this. Hello* h_ptr = new Hello(); World* w_ptr = new World(); typedef boost::signal< int (int, float) > IntFloatSignal; IntFloatSignal sig; sig.connect(boost::bind(&Hello::alternate_int_float, h_ptr, _1, _2)); sig.connect(boost::bind(&World::alternate_int_float, w_ptr, _1, _2)); float temp = 0.0f; sig(1, temp); > I don't see much benefit to extra (explicit) level of indirection here. > Most slots are short bind expressions that don't ever need to be > revisited, so it seems that it could be a bit challenging to determine > where some slots should reside: always in the class containing the > member function that is called (assuming one only uses member > functions!)? I guess I was thinking that since nothing is done with inheritance, it provides less opportunity to do things that might get you into trouble. If I've a hierarchy that looks something like this: BaseObject SimpleObject : BaseObject, signals::trackable ComplexObject : SimpleObject ReallyComplexObject : ComplexObject, signals::trackable where a SimpleObject can get a signal of one type and a ReallyComplexObject object can get another, is trackable inheritance ok with this or is there some other recommended method? Thanks again, Frank -----Original Message----- From: boost-users-bounces(a)lists.boost.org [mailto:boost-users-bounces@lists.boost.org] On Behalf Of Doug Gregor Sent: Tuesday, September 07, 2004 2:38 PM To: boost-users(a)lists.boost.org Subject: Re: [Boost-users] signal slot flexibility On Sep 7, 2004, at 1:36 PM, Frank Maddin wrote: > If I add a function to both Hello and World, from the "Hello World" > example, called alternate() and set up signals like so: > > > > boost::signal<void (Hello*) > sig_h; > > boost::signal< void (World*) > sig_w; > > > > sig_h.connect(boost::mem_fn(&Hello::alternate)); > > sig_w.connect(boost::mem_fn(&World::alternate)); > > > > I have to define two different signals since the object type is part > of the signal definition. Is there an easy way to get a single signal > to call the alternate() function of both Hello and World? Without Hello and World being related (e.g., sharing a base class declaring a virtual "alternate" function), I don't see a way. Still, when you call these signals you have to know whether you have a "Hello" in hand or a "World"; perhaps you wanted to store the "Hello" and "World" objects within the signal, and pass it no arguments? For instance, boost::signal<void()> sig; sig.connect(boost::bind(&Hello::alternate, &my_hello)); sig.connect(boost::bind(&World::alternate, &my_world)); > I recently found this signal slot solution. > http://www.codeproject.com/cpp/ElmueSignalsandSlots.asp > > There is an extra level of indirection here, in that you define a slot > that points to the function. I'd be interested to see what people on > this forum think about this solution. If I understand things > correctly, this solution doesn't seem to fit into the categories > listed in the "Choice of Slot Definitions" docs. I don't see much benefit to extra (explicit) level of indirection here. Most slots are short bind expressions that don't ever need to be revisited, so it seems that it could be a bit challenging to determine where some slots should reside: always in the class containing the member function that is called (assuming one only uses member functions!)? > Also a general signal slot question. What are the main reasons why > developers don't use an inherited pure interface for every callback > type? A signal would be a template class with a list of pointers to > the interface and some methods to operate on the list. Not flexible > enough? You often want only one event out of five, so it's a pain to drop in all of the stubs needed to ignore the other events. Also, you don't get a choice of names to use: if the writer of the interface says it's "on_click", you must write a function named "on_click" even though you'd rather write something like "submit_current_query" that describes the action taken when the event fires, not the event itself (which is essentially irrelevant). > Doesn't scale well to larger uses? Time spent calling virtual > functions? I saw this in the boost signal docs that might apply - > "the use of a large number of small adaptor classes containing virtual > functions has been found to cause an unacceptable increase in the size > of executables (polymorphic class types require more code than > non-polymorphic types)". This is more of an implementation detail; using function pointers instead of virtual functions tends to reduce the amount of code generated for libraries such as Boost.Signals or Boost.Function. Doug _______________________________________________ Boost-users mailing list Boost-users(a)lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users

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signal slot flexibility
by Frank Maddin 07 Sep '04

07 Sep '04

Hi, I have some questions about signals. If I add a function to both Hello and World, from the "Hello World" example, called alternate() and set up signals like so: boost::signal<void (Hello*) > sig_h; boost::signal< void (World*) > sig_w; sig_h.connect(boost::mem_fn(&Hello::alternate)); sig_w.connect(boost::mem_fn(&World::alternate)); I have to define two different signals since the object type is part of the signal definition. Is there an easy way to get a single signal to call the alternate() function of both Hello and World? I recently found this signal slot solution. http://www.codeproject.com/cpp/ElmueSignalsandSlots.asp There is an extra level of indirection here, in that you define a slot that points to the function. I'd be interested to see what people on this forum think about this solution. If I understand things correctly, this solution doesn't seem to fit into the categories listed in the "Choice of Slot Definitions" docs. Also a general signal slot question. What are the main reasons why developers don't use an inherited pure interface for every callback type? A signal would be a template class with a list of pointers to the interface and some methods to operate on the list. Not flexible enough? Doesn't scale well to larger uses? Time spent calling virtual functions? I saw this in the boost signal docs that might apply - "the use of a large number of small adaptor classes containing virtual functions has been found to cause an unacceptable increase in the size of executables (polymorphic class types require more code than non-polymorphic types)". Thanks Frank

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Re: [Boost-users] bjam with mingw
by Brewer, Christopher 07 Sep '04

07 Sep '04

Angus- I had similar problems with bjam under MinGW. By experimentation, I discovered that I could make bjam work under MinGW by moving it from it's previous location at 'c:/msys/1.0/bin' to 'c:/msys/1.0/mingw/bin'. FYI, you can find this thread starting at Boost-users Digest, Vol 250, Issue 1, and ending (successully :) at Boost-users Digest, Vol 253, Issue 1. HTH, Chris Brewer

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