- Boost-users - lists.boost.org

Association Library?
by rzako23 07 May '02

07 May '02

Are there any generic components in Boost (or elsewhere) for *directly* representing associations between classes? Generalization, composition, aggregation and association are major ideas in the object model. Generalization can be implemented fairly directly in C++ using inheritance. Composition and aggregation can be represented directly in C++ using data members (when the number of parts in each whole is small and fixed), or using STL containers (when the number of parts in each whole is large or variable). But Standard C++ (including the STL) provides no *direct* support for representing associations, i.e., collections of links between objects in two or more classes. (David Papurt makes this point in "Inside the Object Model: The Sensible Use of C++.") For example, the STL does not offer a way to *directly* represent the 1-to-many "Supervises" association from the Manager class to the Employee class. One would like to have links in both directions: forward links forthe employees a manager supervises and a back link to the manager each employee is supervised by. Of course, one could code this all "by hand" using a container of pointers to employees for each manager and a back pointer for each employee. But the implementation details really have little to do with managers and employees and would be pretty much the same for parents and children or teachers and students. Moreover, while not difficult, managing the forward and back links correctly (and in an exception-safe manner) is tedious. It would be nice to have templates that can be instantiated to implement specific associations. In brief, STL containers directly support composition and aggregation but not association. I am new to the Boost library, but was not able to find this capability in Boost. If an association library is available in Boost (or elsewhere), I would be happy to know so. If not, is an association library something that would be worth looking into? Thanks, Rob Zako

11 24

Problems building Python lib
by Albrecht Fritzsche 03 May '02

03 May '02

Hi, since I've read in the documentation "Boost.Python is known to have been tested in the following configurations: Against Python 2.0 using the following compiler/library combinations: MSVC++6sp4 with the native library. ... Against Python 1.5.2 using the following compiler/library: MSVC++6sp4 MSVC++6sp4/STLport 4.0" and since I am using the MSVC++6sp4/STLport 4.0 combination I deinstalled Python 2.2 (for which the build failed) and installed Python 1.5.2. Running G:\Environment\boost_1_27_0>jam -sBOOST_ROOT=. -sTOOLS="msvc-stlport" I get the following errors: don't know how to make <python-library@>python21.lib ...patience... ...patience... ...found 2247 targets... ...using 2 temp targets... ...updating 132 targets... ...can't find 1 target... ...can't make 42 targets... msvc-C++-action libs\python\build\bin\libboost_python_static\msvc-stlport\debug\ runtime-link-dynamic\stlport-iostream-off\stlport-version-4.0\types.obj types.cpp .\boost/python/detail/wrap_python.hpp(24) : fatal error C1083: Include-Datei kann nicht geoeffnet werden: 'patchlevel.h': No such file or directory cl /Zm400 -nologo -GX -c -DBOOST_PYTHON_STATIC_LIB=1 -DBOOST_PYTHON_DYNAMI C_LIB -D__STL_NO_SGI_IOSTREAMS=1 -D__STL_DEBUG=1 -D__STL_DEBUG_UNINITIALIZED=1 /Zi /Od /Ob0 /GX /GR /MDd -I"libs\python\build" -I"." -I"c:/tools/python\inclu de" -I"c:/tools/python\PC" -I"\stlport" -I"D:\PROGRA~1\MICROS~1.0\VC98\include" -Fo"libs\python\build\bin\libboost_python_static\msvc-stlport\debug\runtime-li nk-dynamic\stlport-iostream-off\stlport-version-4.0\types.obj" -Tp"libs\python\ build\../src\types.cpp" ...failed msvc-C++-action libs\python\build\bin\libboost_python_static\msvc-stlp ort\debug\runtime-link-dynamic\stlport-iostream-off\stlport-version-4.0\types.ob j ... msvc-C++-action libs\python\build\bin\libboost_python_static\msvc-stlport\debug\ runtime-link-dynamic\stlport-iostream-off\stlport-version-4.0\classes.obj classes.cpp .\boost/python/detail/wrap_python.hpp(24) : fatal error C1083: Include-Datei kan n nicht geoeffnet werden: 'patchlevel.h': No such file or directory ............ [The obvious translation of this error message is: Cannot open include file 'patchlevel.h'.] What am I doing wrong? By the way, all of the other libs including tests are compiling with Jam without any problems at all. And, as a second quesion, why is there no MSVC++6sp4/STLport 4.0 support for the newer Python versions - by the way, there is already a Python v2.2. Thanks for any hints and help Ali *

5 7

Re: [boost] boost organization and installation
by William E. Kempf 02 May '02

02 May '02

----- Original Message ----- From: "David Abrahams" <david.abrahams(a)rcn.com> > > ----- Original Message ----- > From: "William E. Kempf" <williamkempf(a)hotmail.com> > > OK, let me make this a bit more of an official request. If anyone is > > interested in volunteering for this effort send me a private e-mail. > Once I > > have, let's say at least 5, committed volunteers I'll start the effort > of > > creating and coordinating the needed community. > > I don't know whether you want to count me as a volunteer or not. I'm > willing to handle things from the Boost.Build end at some workable pace. > I don't think I can invest anything in other systems, except at the > integration boundary (e.g. if autotools builds Jam and calls it to build > boost). I'd hope that every developer with a current Boost library would be willing to volunteer to at least help with input here, and possibly to committing to some (minor) changes to procedures and/or code. I'm also glad you're volunteering to help from the Boost.Build end of things. But I won't count you as a volunteer for the actual effort here, since I know how busy you are. What I think we really need are volunteers from the user community, though I won't turn down any current Boost developers who think they have the time and experience to help out here. In any event, since I hope that we get volunteers from the user community, I'm CC:ing this to the Boost Users list. Anyone interested in helping out in this effort should e-mail me privately. Bill Kempf

2 1

RE: [Boost-Users] MPL ?
by Aleksey Gurtovoy 01 May '02

01 May '02

Toon Knapen wrote: > Inside a templated class, I need to provide two different > implementations for > a function based on the compile-time decision > ::boost::is_convertible< value_type,double >::value. > How can I do this using MPL ? 1) A simple way: template< typename T > class my { public: typedef typename T::value_type value_type; void foo() { typedef boost::is_convertible< value_type,double > c; do_foo(mpl::bool_c<c::value>()); } private: void do_foo(mpl::true_c) { /*...*/ } void do_foo(mpl::false_c) { /*...*/ } }; Andrei has written an article that covers this technique - http://www.cuj.com/experts/1810/alexandr.htm. 2) A sophisticated one (becomes more relevant when you have several "foo"'s to handle): template< typename T, typename Derived > struct foo_impl { void foo() { Derived& self = static_cast<Derived&>(*this); // ... } }; template< typename Derived > struct foo_double_impl { void foo() { Derived& self = static_cast<Derived&>(*this); // ... } }; template< typename T > class my : public mpl::select_if< boost::is_convertible< typename T::value_type,double > , foo_impl<T, my> , foo_double_impl<T> >::type { // ... private: friend class foo_impl<T, my>; friend class foo_double_impl<T>; // ... }; HTH, Aleksey

1 0

MPL ?
by Toon Knapen 01 May '02

01 May '02

Inside a templated class, I need to provide two different implementations for a function based on the compile-time decision ::boost::is_convertible< value_type,double >::value. How can I do this using MPL ? thanks, toon

1 0

RE: [Boost-Users] shared_ptr and incomplete types
by bjorn.karlsson＠readsoft.com 01 May '02

01 May '02

> From: Jim Hyslop [mailto:jim.hyslop@leitch.com] > > I notice that the implementation available at boost.org does not allow > the single-argument ctor to be called on an incomplete type, e.g.: [snip] > The documentation on the single-argument ctor, though, does not state > that T must be a complete type. Is the implementation > stricter than the > documentation, or is the documentation incomplete? I believe that the implementation is correct, and that belief is confirmed by the latest documentation in the CVS - T must indeed be a complete type. Another change is the addition of a default constructor, which does not require T to be complete. > I'm writing an article on the smart pointers for the CUJ, and I'd like Cool! ;-) > to know if I can correctly state "The default behavior for > shared_ptr is > to require complete types. You can, however, manage an incomplete type > if you provide a function or function object, which will be > called when > the owned object is destroyed." Since shared_ptr requires a complete type only for a few operations, such as the constructor that you mentioned, and reset(T * p), I'd rephrase to something more explicit, like: "The instantiation of a shared_ptr typically requires a complete type. [etc]". Bjorn Karlsson [Non-text portions of this message have been removed]

2 1

shared_ptr and incomplete types
by Jim Hyslop 01 May '02

01 May '02

The documentation at http://www.boost.org/libs/smart_ptr/shared_ptr.htm states that "T may be void, but in that case, either an explicit delete function must be passed in, or the pointed-to object must have a trivial destructor." I notice that the implementation available at boost.org does not allow the single-argument ctor to be called on an incomplete type, e.g.: class simple; simple * createSimple(); shared_ptr<simple> simpleFactory() { return shared_ptr<simple>(createSimple()); } The documentation on the single-argument ctor, though, does not state that T must be a complete type. Is the implementation stricter than the documentation, or is the documentation incomplete? I'm writing an article on the smart pointers for the CUJ, and I'd like to know if I can correctly state "The default behavior for shared_ptr is to require complete types. You can, however, manage an incomplete type if you provide a function or function object, which will be called when the owned object is destroyed." -- Jim

3 2

Graph Library - AllExamples.dsw, anyone got it?
by loopylozzysdad 30 Apr '02

30 Apr '02

Hi All, Just read the excellent Boost Graph Library book. The AllExamples.dsw file is not on the accompanying CD. In the Errata web page (http://siek.info/bgl.html) it says... "On the accompanying CD, the file \BGL\VC++ Projects\AllExamples.dsw is missing. You can download the missing file from here BGLVCprojects.tgz." The file there is a .dsw file but it is NOT the missing one. Has anyone got the real thing? All the best and thanks - Richard Howells

1 0

Re: Boost.Thread (VC specific)
by Holger Thiele 30 Apr '02

30 Apr '02

>-----Ursprungliche Nachricht----- >Von: bill_kempf [mailto:williamkempf@hotmail.com] >Gesendet: Dienstag, 30. April 2002 17:54 >An: Boost-Users(a)yahoogroups.com >Betreff: [Boost-Users] Re: Boost.Thread (VC specific) > > >I don't agree. If it's a good idea, then I'd expect MS to do this by >default for IDE generated builds. Such as default warning level 3? >There's some overhead involved in >generating this, there's compile time overhead (which is important to >some) Do you have figures on that? In my experience, this overhead seems to be a small price to pay for the ability to track bugs (inside your debugger!) on released code. >and there's the fact that many users will be confused by the >presence of debug information and why "stepping" through the code >behaves so strangely and unpredictably. As always, if someone doesn't know what he's doing, there's little help besides getting educated. But, seriously, I think that most users that even get into debugging release builds would surely appreciate library code that supports this. Just my 2 cents. Cheers, and thanks for one of my favorite libraries Holger Thiele D.A.V.I.D. GmbH www.david-gmbh.de

1 0

RE: [Boost-Users] operator == in shared_ptr
by bjorn.karlsson＠readsoft.com 30 Apr '02

30 Apr '02

> From: sashan [mailto:sashang@ihug.co.nz] [snip] > Is there a better way that doesn't involve 1) having to write > a wrapper class around a basic type (or any type) and 2) > doesn't involve changing the shared_ptr::operator==. > As others have pointed out, the solution is to use a function object and std::find_if. In this case, the comparison doesn't even need a separate predicate - the (exceptionally cool) Boost.Bind library can be used instead: vector<shared_ptr<int> >::iterator it=std::find_if(vec.begin(),vec.end(),bind(std::equal_to<int>(),bind(&shared _ptr<int>::operator*, _1),42)); Bjorn Karlsson [Non-text portions of this message have been removed]

1 0