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

RE: [Boost-Users] Problem with boost::any.
by Jim.Hyslop 11 Oct '02

11 Oct '02

Luc Bergeron [mailto:bluc@videotron.ca] wrote: > Greets, > > I'm trying to use the boost::any component but i'm having > problem with > it !!! I'm using it because I need a way to store parameters of > different type. That real fine but I can't retrieve the value > from the > boost::any. This is what i've tried : > > std::string GetStringFromAny(const boost::any& val) const > { > std::string strVal; > try > { > strVal = boost::any_cast<std::string>(val); > } > catch(boost::bad_any_cast &err) > { > std::cerr << err.what() << std::endl; > return ""; > } > return strVal; > } > > But I always have a bad_any_cast exception. From the > documentation, at > leats what I understand of it, "If passed a value or reference, it > returns a copy of the value content if successful". Can > someone point me > in the right direction as to how can I extract the value within a > boost::any type, I think i'm lost !!! :) The following program works for me, without any error (using MSVC6): #include <boost/any.hpp> #include <string> #include <iostream> std::string GetStringFromAny(const boost::any& val) { std::string strVal; try { strVal = boost::any_cast<std::string>(val); } catch(boost::bad_any_cast &err) { std::cerr << err.what() << std::endl; return ""; } return strVal; } int main() { boost::any anAny( std::string("Hello, world") ); std::string converted = GetStringFromAny( anAny ); std::cout << "Converted: [" << converted << "]" << std::endl; } The output, as I expected, was: Converted: [Hello, world] Note that if I add more to main: int main() { boost::any anAny( std::string("Hello, world") ); std::string converted = GetStringFromAny( anAny ); std::cout << "Converted: [" << converted << "]" << std::endl; anAny = 23; converted = GetStringFromAny( anAny ); std::cout << "Converted: [" << converted << "]" << std::endl; } the second conversion fails. The conversion will only succeed if the type that boost::any currently holds can be implicitly converted into the type you want to retrieve. If you want to convert from (for example) an int to a string, you'll need boost::lexical_cast. -- Jim -- Jim

1 0

Problem with boost::any.
by Luc Bergeron 11 Oct '02

11 Oct '02

Greets, I'm trying to use the boost::any component but i'm having problem with it !!! I'm using it because I need a way to store parameters of different type. That real fine but I can't retrieve the value from the boost::any. This is what i've tried : std::string GetStringFromAny(const boost::any& val) const { std::string strVal; try { strVal = boost::any_cast<std::string>(val); } catch(boost::bad_any_cast &err) { std::cerr << err.what() << std::endl; return ""; } return strVal; } But I always have a bad_any_cast exception. From the documentation, at leats what I understand of it, "If passed a value or reference, it returns a copy of the value content if successful". Can someone point me in the right direction as to how can I extract the value within a boost::any type, I think i'm lost !!! :) Thanks in advance for any help. Luc.

2 1

Possible bug in boost_1_28
by Christopher Henrich 11 Oct '02

11 Oct '02

This bug comes up when I try to include <boost/array.hpp> in certain CodeWarrior projects. (CodeWarrior 8.0, running under Mac OS 10.1.5 on G3 "beige tower") If I initialize the project with stationery "C++ Console Mach-O", and I change HelloWorld.cp to include <boost/array.hpp>, then I get this error message: Error: undefined identifier 'ptrdiff_t' suffix.hpp line 204 included from config.hpp: 57 array.hpp:27 HelloWorld.cp: 10 If I initialize with PowerPlant stationery, I do not have this problem. Chris Henrich

6 6

BOOST regex problem using Libarys with Borland Builder 4
by Alastair 11 Oct '02

11 Oct '02

Hi I have just found out about the boost library's so I am new to them. I am trying to use the regex within a VCL Borland Builder 4. I have followed the installation. and tried a given example. I found that the example works well for a console program but for a windows program it seems to crash with the message. EAccessViolation with message ŽAccess violation at address 0040987B. Read address 00000032. I have compiled both within the Borland IDE and I believe that I don't have to do anything and that the IDE and Library will automatically configure itself. What am I doing wrong? Thanks in advance Alastair

2 1

Thread Lib Build errors in xtime.cpp
by Glenn Thorne 10 Oct '02

10 Oct '02

I'm getting the following errors when trying to build Boost using the Intel C++ v6.0 compiler. The build completes as expected with msvc. Is there a problem with boost::uint64_t in this configuration or am I missing a setting somewhere? Any help will be appreciated. Thanks! Glenn ******** C:\boost_1_28_0>set INTELC="C:\Program Files\Intel\Compiler60\IA32" C:\boost_1_28_0>bjam "-sTOOLS=intel-win32" ...found 330 targets... ...updating 12 targets... vc-C++ libs\thread\build\bin\libboost_thread.lib\intel-win32\debug\runtime-link- static\threading-multi\xtime.obj xtime.cpp libs\thread\build\../src\xtime.cpp(80): error: namespace "boost" has no member " uint64_t" const boost::uint64_t TIMESPEC_TO_FILETIME_OFFSET = ((boost::uint64_t) 27111902UL << 32) + (boost::uint64_t)3577643008UL; ^ libs\thread\build\../src\xtime.cpp(80): error: namespace "boost" has no member " uint64_t" const boost::uint64_t TIMESPEC_TO_FILETIME_OFFSET = ((boost::uint64_t) 27111902UL << 32) + (boost::uint64_t)3577643008UL; ^ libs\thread\build\../src\xtime.cpp(80): error: expected a ")" const boost::uint64_t TIMESPEC_TO_FILETIME_OFFSET = ((boost::uint64_t) 27111902UL << 32) + (boost::uint64_t)3577643008UL; ^ libs\thread\build\../src\xtime.cpp(80): error: namespace "boost" has no member " uint64_t" const boost::uint64_t TIMESPEC_TO_FILETIME_OFFSET = ((boost::uint64_t) 27111902UL << 32) + (boost::uint64_t)3577643008UL; ^ libs\thread\build\../src\xtime.cpp(80): error: expected a ";" const boost::uint64_t TIMESPEC_TO_FILETIME_OFFSET = ((boost::uint64_t) 27111902UL << 32) + (boost::uint64_t)3577643008UL; ^ compilation aborted for libs\thread\build\../src\xtime.cpp (code 2) "C:\Program Files\Intel\Compiler60\IA32/bin/icl" /Zm400 -nologo -GX -c /Z 7 /Od /Ob0 /GX /GR MTd -I"libs\thread\build" -I"C:\boost_1_28_0" -I"C:\PROGR A~1\MICROS~3\VC98\include" -I"../include" -Fo"libs\thread\build\bin\libboo st_t hread.lib\intel-win32\debug\runtime-link-static\threading-multi\xtime.obj" -Tp" libs\thread\build\../src\xtime.cpp" ...failed vc-C++ libs\thread\build\bin\libboost_thread.lib\intel-win32\debug\run time-link-static\threading-multi\xtime.obj... ...skipped <libs!thread!build\libboost_thread.lib\intel-win32\debug\runtime-link -static\threading-multi>libboost_thread.CMD for lack of <libs!thread!build\libbo ost_thread.lib\intel-win32\debug\runtime-link-static\threading-multi>xtime.o bj.. . ...skipped <libs!thread!build\libboost_thread.lib\intel-win32\debug\runtime-link -static\threading-multi>libboost_thread.lib for lack of <libs!thread!build\libbo ost_thread.lib\intel-win32\debug\runtime-link-static\threading-multi>xtime.o bj.. . ********

1 0

CVS fails to build
by Björn Lindberg 10 Oct '02

10 Oct '02

Boost CVS isn't working for me right now. When I try to build programs against it I get /home/compbio/d95-bli/include/boost/preprocessor/cat.hpp:18:49: boost/preprocessor/config/config.hpp: Filen eller katalogen finns inte /home/compbio/d95-bli/include/boost/preprocessor/cat.hpp:22:28: missing binary operator before '(' /home/compbio/d95-bli/include/boost/preprocessor/cat.hpp:29:28: missing binary operator before '(' ... Is it (a) a bug, or (b) me doing something wrong, or (c) something else? I am running g++-3.2 on GNU/Linux. Björn

1 0

boost vs. The Lawyers (non-technical)
by Brian Neal 10 Oct '02

10 Oct '02

I hope this is appropriate for this mailing list... I am a software engineer and our development team loves boost. However, I can already see a coming battle with our company lawyers trying to convince them to let us use boost in our software. We informally talked with one of our software quality engineers. He said their major concern would be assuring that we had permission to use the boost software. In other words, how would we know that the boost developers had permission to release their libraries so that anyone could use it? He also thought we would need something in writing to this effect. Since their isn't any official boost organization, I am getting scared already. I am not a lawyer, nor do I play one on TV, but I would like to hear from any boost developer or user who has experiences in dealing with this nonsense. 1) How did you get your company lawyers off your backs and let you use boost? 2) Should there be (is there?) a central boost license that all boost libraries have that we can point our lawyers at, instead of going to each and every boost developer to get permission to use his/her library? 3) What has been your experience in this situation? Its ironic that something as wonderful as boost, which gives us so much productivity (and that savings is passed along to our customers) could be considered so dangerous by our lawyers. Again, if this is not appropriate or has been rehashed to death I apologize. If that is the case, please email me off list. I'll collect the responses and give them to anyone who is interested. Thanks, Brian Neal

4 3

tuple vs SGI/MIPSPro
by Kevin Wheatley 10 Oct '02

10 Oct '02

Hi, I'm starting to get to grips with boost and in particular on the SGI platform. I was trying to use the boost::tuples and found that with the SGI compiler v7.3.1.3m I was getting the following error CC -LANG:std -I/images/src/boost/from_cvs/boost -I/images/src/boost/from_cvs/boost/boost/compatibility/cpp_c_headers/ -o tupple tupple.cpp cc-1239 CC: ERROR File = /images/src/boost/from_cvs/boost/boost/tuple/tuple_io.hpp, Line = 113 "close" is ambiguous. case close : c = i.widen(')'); break; ^ A template was detected during header processing. instantiation of "char boost::tuples::detail::format_info::get_manipulator(std:: basic_ios<char, std::char_traits<char>> &, boost::tuples::detail::format_info::manipulator_type)" at line 437 instantiation of "std::basic_istream<char, std::char_traits<char>> &boost::tuples::detail::extract_and_check_delimiter(std:: basic_istream<char, std::char_traits<char>> &, boost::tuples::detail::format_info::manipulator_type)" at line 511 instantiation of "std::basic_istream<char, std::char_traits<char>> &boost::tuples::operator>>(std::basic_istream<char, std::char_traits<char>> &, boost::tuples::cons<double, boost::tuples::detail::map_tuple_to_cons<double, double, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type>::type> &)" at line 630 of "/usr/include/CC/stl_iterator.h" instantiation of "void std::istream_iterator<density, char, std::char_traits<char>, ptrdiff_t>::_M_read()" at line 604 of "/usr/include/CC/stl_iterator.h" instantiation of "std::istream_iterator<density, char, std::char_traits<char>, ptrdiff_t>::istream_iterator(std::istream_iterator<densit y, char, std::char_traits<char>, ptrdiff_t>::istream_type &)" at line 19 of "tupple.cpp" I'm working with the code from CVS because it compiled better on the SGI, I looked at the code, and basically I think it's getting confused due to my test program including a "using namespace std;" so I modified the tuple_io.hpp to specifically mention detail::format_info::close rather than the bare close and then my example works (I also made explicit the other cases of the switch statement). Is there a more recomended way of doing this? Almost everywhere else in that file the full specification of the enum is given. My code is something like: #include <vector> #include <iostream> #include <algorithm> #include <numeric> #include <iterator> #include "boost/tuple/tuple.hpp" #include "boost/tuple/tuple_comparison.hpp" #include "boost/tuple/tuple_io.hpp" using namespace std; using namespace boost::tuples; typedef tuple<double, double, double> density; int main() { vector<density> v; istream_iterator<density> in(cin); istream_iterator<density> eos; ostream_iterator<density> out(cout); density total; copy(in, eos, back_inserter(v)); copy(v.begin(), v.end(), out); cout << endl; return 0; } Thanks Kevin -- | Kevin Wheatley | These are the opinions of | | Senior Do-er of Technical Things | nobody and are not shared | | Cinesite (Europe) Ltd | by my employers |

1 0

Building regex on AIX w VisualAge
by Tim Daplyn 10 Oct '02

10 Oct '02

Can anyone assist me with this? I've tried every compiler option I can think of combined with disabling BOOST support for a whole bunch of stuff and I still can't get this library to build on AIX. There are just too many compile errors, and I was really hoping I wouldn't have to go modifying the source.

2 1

How to Create Calculated Internal Properties?
by Phillip Ratzloff 10 Oct '02

10 Oct '02

I wish to create an internal calculated property that is derived from existing properties in a vertex or edge. Id also like to be able to access it like any other internal property. For instance, I want a vertex property called weight_sum that would sum the weights for all the out edges and return the answer. I want to be able to use a statement "get(vertex_weight_sum,G,v)" to get the value. Later on, I may decide that I want to cache the value on the vertex (like a normal property) and existing code should work without change. I have been unable to figure out any template class specializations to do this. Additionally, if I try to define the property using the property<> template in the graph declaration it reserves storage for the property, which is undesired. Am I missing something? Is there a way to define a calculated internal property that doesnt reserve storage?

1 0

using weak_ptr and shared_ptr for singleton
by Stephan Born 09 Oct '02

09 Oct '02

Hello! I do some experiments on shared_ptr and weak_ptr. So I tried to use them for a singleton-class, which does not need an explicit singleton::release_instance method. The singleton-instance will be destroyed everytime the last external shared_ptr holding the instance goes out of scope. Is this a valid usage for weak_ptr? Are there any traps I do not see using these smart_ptrs in this context? The drawback of using shared_ptr with singleton is the need for a public destructor. But this is dangerous....it is possible to write singleton::singleton_ptr first_ptr = singleton::instance(); delete first_ptr.get(); Declaring the destructor as private is only possible when defining boost::checked_delete as friend of the singleton-class. ( there is a thread on comp.lang.c++.moderated with the topic 'specialization of function template as friend with MSVC6SP5 not possible' which deals with this problem of friendship... ) But then it is still possible to write the following code singleton::singleton_ptr first_ptr = singleton::instance(); boost:checked_delete( first_ptr.get() ); OK, it's very unlikely to do it by chance, but it is possible. Is there a way to allow destruction of the instance only to shared_ptr? <code> #include <boost/shared_ptr.hpp> #include <boost/weak_ptr.hpp> #include <boost/utility.hpp> class singleton : boost::noncopyable { public: typedef boost::shared_ptr< singleton > singleton_ptr; static singleton_ptr instance() { singleton_ptr tmp; if( s_instance.expired() ) { tmp.reset( new singleton ); s_instance = tmp; } else { tmp = boost::make_shared( s_instance ); } return tmp; } void foo() { // do something i++; } // like to make it private in order to prohibit delete on it, // but boost::shared_ptr<> can't handle it....so sad :( ~singleton(){}; private: typedef boost::weak_ptr< singleton > internal_singleton_ptr; singleton(){}; int i; static internal_singleton_ptr s_instance; }; singleton::internal_singleton_ptr singleton::s_instance; int main() { { singleton::singleton_ptr first_ptr = singleton::instance(); { singleton::singleton_ptr second_ptr = singleton::instance(); second_ptr->foo(); } first_ptr->foo(); } singleton::singleton_ptr another_ptr = singleton::instance(); another_ptr->foo(); return 0; } </code> Regards, Stephan -- --------------------------------------------------------------- Dipl.-Inf. (FH) Stephan Born | beusen Solutions GmbH fon: +49 30 549932-0 | Landsberger Allee 366 fax: +49 30 549932-21 | 12681 Berlin mailto:stephan.born@beusen.de | Germany --------------------------------------------------------------- PGP-Key verfügbar | PGP-Key available ---------------------------------------------------------------

3 6

Regex Access violation in BCB5
by Tim Daplyn 09 Oct '02

09 Oct '02

I've used a previous version of the boost regex library before and have just upgraded to the latest version. Built the libs and dll fine, but now I get a A/V when calling any boost code. I've even set up a vanilla console app with all the Borland default settings and the following code: #include "boost/regex.hpp" int main(int argc, char* argv[]) { boost::wregex regExpr2(L"bill.*"); bool result; result = boost::regex_match(L"freddy", regExpr2); result = boost::regex_match(L"billabong", regExpr2); return 0; } And it blows up on the first regex_match!! I can't figure out what's going on - I know it's linking to the _sdi version of the lib because it complains about it being missing if I remove it, and the dlls are on the path and are loaded as soon as this mini-app starts up. It makes no difference whether I build through the command line or in BCB GUI. Please help!! Thanks, Tim D.

1 0

building smart_ptr as a separate library
by Nik Kolev 07 Oct '02

07 Oct '02

Hi everybody: Is it possible to build/integrate just the smart_ptr part of boost. If yes I would greatly apreciate your suggestions on how this is to be accomplished. Thanks, Nik

2 1

RE: [Boost-Users] Iterator adapters and maps
by scleary＠jerviswebb.com 04 Oct '02

04 Oct '02

I think the problem is in the definition of Select2ndRef; if you use: template<class pair_type> struct Select2ndRef { typedef pair_type argument_type; typedef typename pair_type::second_type result_type; result_type & operator()(pair_type & source) const { return source.second; } }; then your code will compile. This has to do with an unusual meaning of "result_type" for projection iterator adaptors. -Steve

2 1

Use a shared_ptr as a 'backpointer'?
by dick.bridges＠tais.com 04 Oct '02

04 Oct '02

I run into situations where it's useful for an object to have a 'backpointer' to the object instance that created it (example below). Is there a pattern/idiom for doing this using shared_ptr? Or maybe I need to re-think the idea of the backpointer in the first place? class Bar; class Foo { public: Foo(Bar* b) : p(b){} private: Foo() : p(0){} shared_ptr<Bar> p; } class Bar { void doit() { new Foo(???); // <<< new Foo(this) obviously won't work. } }

3 2

[BGL]: 2 desgin questions
by Björn Lindberg 03 Oct '02

03 Oct '02

I have two questions regarding the design of the BGL. I'm interested in this to get a better understanding of the design choices, which influences how I use the BGL and how I'm building on it. 1) Why is a lot of the function arguments made by value rather than reference? As an example, consider the BFS algorithm, where the documentation states that "[1] Since the visitor parameter is passed by value, if your visitor contains state then any changes to the state during the algorithm will be made to a copy of the visitor object, not the visitor object passed in. Therefore you may want the visitor to hold this state by pointer or reference." It would be much easier to use the visitor objects for keeping state throughout the algorithm if it was passed by reference instead. 2) Non-constness. It seems impossible to use BGL together with code that is "const-correct". If, for instance, I have a function implementing some kind of examining algorithm on a graph (so the graph is passed to it as const), and this algorithm uses breadth_first_search with a visitor that doesn't modify the graph, it still can't be const when passed to breadth_first_search. This only leaves the options of either (i) casting away constness in the call, which is bad because it could introduce bugs later on, or (ii) leaving out const altogether which is not good either. Maybe I've just misunderstood something and this is possible, or perhaps it is impossible to implement BGL in this way? Björn

2 2

boost build on redhat7.3
by Alkis Evlogimenos 03 Oct '02

03 Oct '02

Hi, I just compiled boost from cvs. I am using an x86 with redhat linux 7.3. I also have STLport 4.5.3 installed. I compiled against STLport using this command: bjam "-sTOOLS=gcc-stlport" "-sSTLPORT_INCLUDE_DIRECTORY=include/stlport" "-sSTLPORT_LIB_DIRECTORY=lib" "-sSTLPORT_ROOT=/usr" and against gcc using the following: bjam "-sTOOLS=gcc" Both builds finish with success (compiling with j4 leaves 2 targets behind but they succeed after a reinvocation). Now I enter status/ and compile regression using the following: g++ -I.. regression.cpp -o regression Modify compiler.cfg to look like: linux gcc-296 GCC 2.96 g++ -c -Wall -W -ftemplate-depth-30 -I%include %source g++ -o boosttmp.exe -Wall -W -ftemplate-depth-30 -I%include %source -lrt GNU <a href="http://gcc.gnu.org/">GCC</a> 2.96 linux gcc-296-stlport GCC 2.96 STLport 4.5 g++ -c -Wall -W -ftemplate-depth-30 -isystem /usr/include/stlport -I%include %source -lstlport_gcc g++ -o boosttmp.exe -Wall -W -ftemplate-depth-30 -isystem /usr/include/stlport -I%include %source -lrt -lstlport_gcc GNU <a href="http://gcc.gnu.org/">GCC</a> 2.96 <a href="http://www.stlport.org/">STLport</a> 4.5 and finally run regression as follows: ./regression -o cs-rh7.3.html Attached is a gzipped log of the regression run. The text was 429Kb so I didn't paste it to this email :-) It seems that the testing frameworks has some problems (libs/config/test/config_test.cpp fails). Am I doing something wrong here? Any help is appreciated. Thanks, -- Alkis [Non-text portions of this message have been removed]

1 1

[BGL] Daisy chaining algorithms using vistor mechanism?
by Chris Russell 02 Oct '02

02 Oct '02

Still up hacking... Without cluttering the question with a ton of detail, basically I need to perform a DFS on a forest stored in a bidirectionalS adjacency_list and then perform a subgraph traversal in response to each finish_vertex invocation in the visitor. (The idea is to push information down the branches towards the root of a tree in the forest). Calling in_edges(v,g) from within the finish_vertex method in a dfs_visitor will not compile however. This is because the graph is passed by const reference into the visitor method and in_edges requires a non-const graph reference? (this seems similar in spirit to a question I posted a week or two ago about boost::get(some_property, Graph) from within a visitor). Generally, I would like to be able to daisy chain graph algorithms - that is invoke a sub-algorithm from within a visitor method called by a controlling algorithm. This would require that the sub-algorithm not change the graph topology, trample on properties used by its controller (e.g. coloring), or otherwise invalidate vertex descriptors or iterators so some care would need to be taken in designing the sub-algorithm. But it seems like a useful mechanism for extension. Am I missing something about getting at the in_edges given that I'm working with a const graph_t& in the context of the "controlling" DFS' visitor method? Why is this so restrictive? I'm guessing it might have something to do with having multiple copies of vertex and edge iterators floating around but I'm not sure. Will you comment on this please Jeremy? Thank you. - Chris Russell

5 6

RE: [Boost-Users] MPL?
by Mark Storer 02 Oct '02

02 Oct '02

"Modern C++ Design" has a pretty good coverage so far (I'm on chapter 6 out of 11). As for impressing the ladies... well... you could always show them your stamp collection. --Mark Storer Software Engineer Cardiff Software #include <disclaimer> typedef std::disclaimer<Cardiff> Discard; -----Original Message----- From: Jeff Faust [mailto:jeff@opticalres.com] Sent: Wednesday, October 02, 2002 12:37 PM To: Boost-Users(a)yahoogroups.com Subject: RE: [Boost-Users] MPL? Well, I didn't know I needed boost until I saw it. Same for STL several years back. 'Metaprogramming' comes up a lot on the boost list, but I have no understanding about what it's for--what problems it solves. The documentation is sparse. Then this thread comes up and everybody talks about it like it's obvious. I dislike being baffled. But mostly it's curiosity. I need something to talk about at parties and impress the ladies. MPL will do that, right? Right? Hello? Jeff -----Original Message----- From: David B. Held [mailto:dheld@codelogicconsulting.com] Sent: Wednesday, October 02, 2002 12:14 PM To: Boost-Users(a)yahoogroups.com Subject: Re: [Boost-Users] MPL? ----- Original Message ----- From: "Jeff Faust" <jeff(a)opticalres.com> To: <Boost-Users(a)yahoogroups.com> Sent: Wednesday, October 02, 2002 11:32 AM Subject: [Boost-Users] MPL? > [...] > Can anybody explain in English what the following does? I believe that Aleksey posted the runtime pseudo-equivalent. > Posted by David Abrahams on boost developers list: > > Have I mentioned recently how totally cool MPL's lambda facility is? > > I can't believe I can do things like this, even with MSVC6. It makes my > > metaprograms SO much easier to manage! > > mpl::logical_and< > > is_reference_to_class<add_reference<mpl::_> > > > , mpl::logical_not< > > is_reference_to_args<add_reference<mpl::_> > [Aleksey, on 9/27] // "ideal" version, for comparison purposes: // is_reference_to_class( add_reference(_) ) // && !is_reference_to_args( add_reference(_) ) I can't say for sure what the code does myself, but if I could venture a guess, I would say that it's a condition for something else (maybe an iterative algorithm over a type container?) that checks to see if an argument is a reference type of various sorts. Basically, if you don't understand it, in this case, you probably don't need it. ;) I know I don't! Dave Info: <http://www.boost.org> Wiki: <http://www.crystalclearsoftware.com/cgi-bin/boost_wiki/wiki.pl> Unsubscribe: <mailto:boost-users-unsubscribe@yahoogroups.com> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/ Info: <http://www.boost.org> Wiki: <http://www.crystalclearsoftware.com/cgi-bin/boost_wiki/wiki.pl> Unsubscribe: <mailto:boost-users-unsubscribe@yahoogroups.com> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/

3 2

RE: [Boost-Users] MPL?
by Randy Bowen 02 Oct '02

02 Oct '02

Metaprogramming techniques are discussed pretty thoroughly in Andrei Alexandescru's "Modern C++ Design" and in Czarnecki and Eisenecker's "Generative Programming". --Randy -----Original Message----- From: Jeff Faust [mailto:jeff@opticalres.com] Sent: Wednesday, October 02, 2002 12:37 PM To: Boost-Users(a)yahoogroups.com Subject: RE: [Boost-Users] MPL? Well, I didn't know I needed boost until I saw it. Same for STL several years back. 'Metaprogramming' comes up a lot on the boost list, but I have no understanding about what it's for--what problems it solves. The documentation is sparse. Then this thread comes up and everybody talks about it like it's obvious. I dislike being baffled. But mostly it's curiosity. I need something to talk about at parties and impress the ladies. MPL will do that, right? Right? Hello? Jeff -----Original Message----- From: David B. Held [mailto:dheld@codelogicconsulting.com] Sent: Wednesday, October 02, 2002 12:14 PM To: Boost-Users(a)yahoogroups.com Subject: Re: [Boost-Users] MPL? ----- Original Message ----- From: "Jeff Faust" <jeff(a)opticalres.com> To: <Boost-Users(a)yahoogroups.com> Sent: Wednesday, October 02, 2002 11:32 AM Subject: [Boost-Users] MPL? > [...] > Can anybody explain in English what the following does? I believe that Aleksey posted the runtime pseudo-equivalent. > Posted by David Abrahams on boost developers list: > > Have I mentioned recently how totally cool MPL's lambda facility is? > > I can't believe I can do things like this, even with MSVC6. It makes my > > metaprograms SO much easier to manage! > > mpl::logical_and< > > is_reference_to_class<add_reference<mpl::_> > > > , mpl::logical_not< > > is_reference_to_args<add_reference<mpl::_> > [Aleksey, on 9/27] // "ideal" version, for comparison purposes: // is_reference_to_class( add_reference(_) ) // && !is_reference_to_args( add_reference(_) ) I can't say for sure what the code does myself, but if I could venture a guess, I would say that it's a condition for something else (maybe an iterative algorithm over a type container?) that checks to see if an argument is a reference type of various sorts. Basically, if you don't understand it, in this case, you probably don't need it. ;) I know I don't! Dave Info: < http://www.boost.org> Wiki: < http://www.crystalclearsoftware.com/cgi-bin/boost_wiki/wiki.pl> Unsubscribe: <mailto:boost-users-unsubscribe@yahoogroups.com> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/ Yahoo! Groups Sponsor ADVERTISEMENT <http://rd.yahoo.com/M=233351.2428261.3848243.2225242/D=egroupweb/S=17050067…> <http://us.adserver.yahoo.com/l?M=233351.2428261.3848243.2225242/D=egroupmai…> Info: < http://www.boost.org> Wiki: < http://www.crystalclearsoftware.com/cgi-bin/boost_wiki/wiki.pl> Unsubscribe: <mailto:boost-users-unsubscribe@yahoogroups.com> Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service <http://docs.yahoo.com/info/terms/> . [Non-text portions of this message have been removed]

1 0

Iterator adapters and maps
by Alisdair Meredith 02 Oct '02

02 Oct '02

I have a std::map<std::string, MyObject> and want to iterate over it calling several member functions of MyObject. This seems like a good case to learn about transform/projection iterator, but I am having a hard time getting a compiling example. My most recent attempt looks like this: class MyObject { public: void CommitChanges(); void RollbackChanges(); // More implementation details would follow }; typedef std::map<std::string, MyObject> MyMap; typedef MyMap::iterator MyIterator; typedef MyMap::value_type mapped_type; typedef boost::projection_iterator_generator< Select2ndRef<mapped_type>, MyIterator >::type projection; MyMap theMap; projection begin( theMap.begin() ); projection end( theMap.begin() ); for_each( begin, end, mem_fun_ref( MyObject::CommitChanges ) ); I also have the following two templates, although I suspect their equivalent must be lurking in boost somewhere: template<class pair_type> struct Select1stRef { typedef typename pair_type::first_type & result_type; result_type operator()( pair_type &source ) const { return source.first; } }; template<class pair_type> struct Select2ndRef { typedef typename pair_type::second_type & result_type; result_type operator()( pair_type &source ) const { return source.second; } }; I am compiling using BCB5 compiler in the IDE, should be equivalent to the free 5.5.1 command line compiler. While I could simply write a forwarding functor in a fraction of the time it will take me to solve this, there is definitely a ne tool I would like to add to my toolbox here once I understand what is happenning. Unfortunately I am getting somewhat lost in reference-to-reference issues, and the occasional compiler crash does not help. Any and all hints appreciated -- AlisdairM

1 0

Loki vs. Boost
by Hamlet 02 Oct '02

02 Oct '02

Hi, I'm (desperately) looking for a serious comparative review of Loki vs. Boost libraries. Although the differences are quite clear, still it would be nice to see a serious comparison, especially in the features that exists in both places, i.e. smart pointers, small obj. allocator, type traits and template meta-programming. Does anybody knows if there exists such a paper somewhere, or alternatively have his own insights about the libraries? Thanks, Ariel

2 1

[BGL] vertex_index_t w/VertexList=listS questions
by Chris Russell 02 Oct '02

02 Oct '02

Hi Jeremy, Using adjacency_list w/VertexList=listS, I've stuffed a vertex_index_t declaration into the internal vertex property map and got my DFS invocation to compile. Taking a look at the dijkstra-example-listS.cpp in the examples directory on CVS, I see how you manually initialize this property for each of the vertices after you build up the graph. p.230 of the book discusses the auto-update of the vertex_index_t property upon vertex removal for the case of VertexList=vecS but I'll need to affect this update myself for VertexList=listS? Also, can you foresee any problems if I register vertex_index_t with a value_type of long int instead of int? I'm guessing no because I'm passing it as a template parameter but I just want to make sure. - Thanks and regards Chris Russell

2 1

BOOST_PARAM_TEST_CASE and uncaught exceptions
by Alisdair Meredith 02 Oct '02

02 Oct '02

I have a case where my test case passed to BOOST_PARAM_TEST_CASE is throwing an exception I was not expecting. This seems to still result in the correct number of calls to the test case, but the first parameter in the list is passed every time. Is this a feature of my compiler, or an issue with the library? Using Borland C++ Builder 5 (should be same as free command-line compiler) -- AlisdairM

2 1

BUG: intrusive pointer and weak_ptr
by Petr Ferschmann 01 Oct '02

01 Oct '02

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hello, I think I found BUG. Let we have this program: - -- cut here -- #include <boost/shared_ptr.hpp> #include <boost/weak_ptr.hpp> #include <boost/intrusive_ptr.hpp> #include <cstdio> using namespace std; #define INTR class MujObjekt #ifdef INTR : public boost::counted_base #endif { public: MujObjekt() { printf( "MujObjekt::MujObjekt()\n" ); } void setThis( boost::shared_ptr<MujObjekt> obj ) { m_this = obj; } virtual ~MujObjekt() { printf( "MujObjekt::~MujObjekt()\n" ); } boost::weak_ptr<MujObjekt> m_this; }; int main() { boost::shared_ptr<MujObjekt> obj( new MujObjekt() ); obj->setThis( obj ); return( 0 ); } - --- cut here --- But in case of usage of intrusive pointer it doesn't call destructor - because there is weak pointer. But when I undefine INTR and it uses non-intrusive it works as expected. This is only modelling case to simulate bug. - -- Petr "Fers" Ferschmann -=[ petr(a)ferschmann.cz ]==[ http://petr.ferschmann.cz/ ]=- - -=[ Koukni na http://www.postcard.cz/ ]==[ +420 604/781 009 ]=- GPG Fingerprint: [83B0 6378 7A9D D993 035E 60BD FEEC F665 D2C8 1B9A] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.0.7 (GNU/Linux) iD8DBQE9mV9O/uz2ZdLIG5oRArF/AJ9LGfWTXfy69zNTsbiEKThTPQnWcwCeOWgj 0tX9AxdWJ8u/L1MkdZHjOPk= =7A3i -----END PGP SIGNATURE-----

3 3