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boost mutex locking order
by amiel montecillo 22 Nov '04

22 Nov '04

Hi all, i was supposed to use boost::mutex in my multithreaded app, and came across a problem with its scheduling policy. if more than one thread is going to use the mutex object, how can we implement the FIFO scheduling policy? i need it so that other threads waiting for the mutex to be unlocked can acquire it in order in which they waited on the mutex that is accessed through boost::mutex::scoped_lock.

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boost::variant output a vector?
by Bo Peng 21 Nov '04

21 Nov '04

Dear list, In the manual of boost::variant: OutputStreamable: For any object t of type T, std::cout << t must be a valid expression. However, I can not output a variant vector work by defining ostream& operator<< vector<double> . Attached is a test case. Note that variant int, string can be outputed, but not the vector. Yet, cout << vector<double> is working. I am using gcc 3.2.2 on linux redhat 9. Many thanks in advance. Bo #include "boost/variant.hpp" using namespace std; #include <string> #include <vector> typedef boost::variant<int, double, string, vector<double> > Variable; #include <iostream> ostream& operator<< (ostream& out, const vector<double> & vec) { out<< "["; if( ! vec.empty() ) { vector<double>::const_iterator it = vec.begin(); out << *it; for( ++it; it!= vec.end(); ++it) out << ", " << *it ; } out << "]"; return out; } int main() { Variable a(2); Variable b("asd"); vector<double> vec(0); vec.push_back(3.0); Variable c(vec); cout << vec << endl; // OK cout << a << b << endl; // OK cout << c << endl; // compiling errors. return 0; }

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serialization example linker errors.
by Jeffrey Holle 21 Nov '04

21 Nov '04

My boost libaries come from CVS on Sun Nov 14 18:35:14 EST 2004 I'm building with gcc v3.4.2 on a linux system. I've run into a problem in attempting to build the serialization examples. All failed in link phase with: /usr/bin/ld: cannot find -lm

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Luabind and Boost 1.32.0
by Jeremy Swigart 21 Nov '04

21 Nov '04

Just grabbed the latest version and attempted to compile a previously working setup of Luabind and I get the following error. \luabind\class.hpp(105) : fatal error C1083: Cannot open include file: 'boost/mpl/apply_if.hpp': No such file or directory Apparently this file was removed in boost 1.32 Anyone know how to get luabind back to a working state? Thanks. Jeremy

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Re: [sigc] Re: [Boost-users] Signals & Slots
by Edward Diener 20 Nov '04

20 Nov '04

Carl Nygard wrote: > On Thu, 2004-11-18 at 14:09, Doug Gregor wrote: >> On Nov 18, 2004, at 1:10 PM, Murray Cumming wrote: > >> I'm not in a position to do this at the moment, although possibly in >> the future. It would be *wonderful* if someone went off and studied >> both libraries in-depth to make this comparison, especially if that >> person was not intimately familiar with either library beforehand. >> > > Available: http://www.3sinc.com/opensource/boost.bind-vs-sigc2.html > > Updates for code samples from Chris Vine and Jonathan Brandmeyer will > be forthcoming. > > I could use some suggestions on how to incorporate common code into > the code comparison tables. > > And of course, any other comments, flames, etc. will be welcome. I'm > only doing this as a service for keeping track of comments. I'd like > to see some of this stuff make it into the C++ standard library. In the just-released Boost 1.32, the Boost signals library does make a guarantee of the order of signals within a particular group. The order within a particular group is FIFO.

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Re: [sigc] Re: [Boost-users] Signals & Slots
by David Abrahams 20 Nov '04

20 Nov '04

Carl Nygard <cjnygard(a)fast.net> writes: > On Thu, 2004-11-18 at 14:09, Doug Gregor wrote: >> On Nov 18, 2004, at 1:10 PM, Murray Cumming wrote: > >> I'm not in a position to do this at the moment, although possibly in >> the future. It would be *wonderful* if someone went off and studied >> both libraries in-depth to make this comparison, especially if that >> person was not intimately familiar with either library beforehand. >> > > Available: http://www.3sinc.com/opensource/boost.bind-vs-sigc2.html > > Updates for code samples from Chris Vine and Jonathan Brandmeyer will be > forthcoming. > > I could use some suggestions on how to incorporate common code into the > code comparison tables. > > And of course, any other comments, flames, etc. will be welcome. I'm > only doing this as a service for keeping track of comments. The syntax you're using for boost::function is a bit passe. // Signal with two args and int return value boost::signal2<int, float, string> sig; Should be // Signal with two args and int return value boost::signal<int (float, string)> sig; I think your analysis underestimates or ignores the importance of syntax, most importantly the syntax for invoking a signal. The fact that the Boost signal is an ordinary function object that can be called directly has important implications for interoperability (you don't need binders). NOTE: Boost.Signals documentation states that there are exceptions to using boost::signals::trackable, specifically the trackable base class is unable to manage connections created using Boost.Function or Boost.Lambda. This problem is stated to be resolved in future versions. Trackable Boost.Signals is at a bit of a disadvantage because the trackable class doesn't work with Boost.Lambda and Boost.Function. In this bsense, SigC library's implementation seems superior, if only because you don't have to think about limitations. Does libSigC++ not suffer from an analogous limitation, or did its documentation simply fail to mention it, or is just requiring you to do more work manually? The equivalency table for slot binders is misleading, I think. Boost.Signals has no direct coupling to Boost.Bind, and the fact that Boost.Bind doesn't provide certain binders doesn't mean you can't get them another way. For example, I think you can use Boost.Lambda or Phoenix to create them. As for the retype ... stuff, I don't know what libSigC++ does there. However, no explicit retyping is needed with Boost where the types concerned are implicitly convertible to the expected types. Hope this helps. -- Dave Abrahams Boost Consulting http://www.boost-consulting.com

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POSIX regex library conflicts
by Andrew Dennison 20 Nov '04

20 Nov '04

My project hit an interesting snag yesterday. It turns out that in different areas of the project, one developer had been using the boost regex library, while the other was using the POSIX library. Since the boost regex library provides POSIX compatibility with boost/regex.h i suspect you may already be aware of this, but i'll mention it anyway, as i believe more could be done about this problem. regex.h uses #defines for certain numerical constants which are also declared in boost regex. This is a problem if both posix and boost are defined in the same project at the same time as the preprocessor will replace the boost definitions with the macro definition in regex.h (ie REG_EXTENDED = 1, among others). I appreciate that this case is somewhat handled by the compatibility header, but this isn't always an available solution. We were able to change headers, so this problem was solved, but this may not always be possible (ie third party software). Perhaps the developers could include some protection against this kind of error by checking to see if the offending constants are defined before the boost declarations are made and #undef-ing them as needed. This kind of error can be difficult to track down in mid-large projects. Regards, Andrew.

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Boost 1.32.0 released
by Aleksey Gurtovoy 20 Nov '04

20 Nov '04

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ + NOTE: This is a stripped-down copy of the Boost 1.32.0 release + + notes. See http://www.boost.org for the full version. + ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Important - New Toolset Names ----------------------------- The names of some the Boost.Build toolsets have been changed to remove the "." (dot) character and to fix some other naming inconsistencies. For example, vc7.1 toolset was renamed to become vc-7_1. Please refer to the Supported Toolsets section of the installation guide for the complete list of the current toolset names. This change was made as a part of the effort to make the Boost distribution compatible with ISO 9660 level 2 requirements. New Libraries ------------- * Assignment Library: Filling containers with constant or generated data has never been easier, from Thorsten Ottosen. * Minmax Library: Standard library extensions for simultaneous min/max and min/max element computations, from Herv Brnnimann. * Multi-index Containers Library: Containers with multiple STL-compatible access interfaces, from Joaqun M Lpez Muoz. * Numeric Conversion Library: Optimized policy-based numeric conversions, from Fernando Cacciola. * Program Options Library: Access to configuration data given on command line, in config files and other sources, from Vladimir Prus. * Range Library: A new infrastructure for generic algorithms that builds on top of the new iterator concepts, from Thorsten Ottosen. * Serialization Library: Serialization/de-serialization of arbitrary C++ data structures to various formats including text, binary, and xml, from Robert Ramey. * String Algorithms Library: Collection of string related algorithms for case conversion, trimming, find/replace operations and more, from Pavol Droba. * Tribool: 3-state boolean type library, from Doug Gregor. Updated Libraries ----------------- * Compose: This deprecated library has been removed. * Graph: - Added bundled properties to the adjacency_list and adjacency_matrix class templates, greatly simplifying the introduction of internal vertex and edge properties. - The LEDA graph adaptors have been ported to LEDA 4.5. - Added algorithms for betweenness centrality and betweenness centrality clustering. - Added circle layout and undirected spring layout algorithms. * MPL Library: - Updated to use the Boost Software License. - New documentation, including a complete reference manual. - Major interface changes and improvements, many of which are not backward compatible. Please refer to the 1.32 changelog for the detailed information about upgrading to the new version. * Python Library: - Updated to use the Boost Software License. - A new, better method of wrapping classes with virtual functions has been implemented. - Support for the new Python Bool type, thanks to Daniel Holth. - Support for upcoming GCC symbol export control features have been folded in, thanks to Niall Douglas. - Improved support for std::auto_ptr-like types. - Components used by other libraries have been moved out of python/detail and into boost/detail to improve dependency relationships. - Miscellaneous bug fixes and compiler workarounds. * Signals Library: Introduced deterministic slot ordering, permitting slots to be connected at the beginning or end of slot groups or the slot list itself. Combiners may safely have state and are accessible from the signal. * Utility: class template result_of added. * Test Library: - namespace names gets shorten; old one still supported till next release. - added proper encoding of XML PCDATA. - support for wide string comparison implemented. For complete list of changes see Test Library release notes. Regression tests ----------------- This release has been extensively tested on a variety of different compilers and platforms. It is known to contain no regressions against the previous reference release on the compilers and configurations tested. Please refer to the corresponding regression reports at http://www.meta-comm.com/engineering/boost-regression/1_32_0 to see how well your compiler performs on the new Boost codebase. Acknowledgements ---------------- This release wouldn't have been possible without the dedicated effort of many, many members of the Boost community who generously contributed their outstanding expertise, time and energy to making it happen. For patches, bug fixes, troubleshooting, expert advice, and prompt responses to the release manager's requests we thank: David Abrahams, Misha Bergal, Jonathan Brandmeyer, Fernando Cacciola, Marshall Clow, Christopher Currie, Pavol Droba, Caleb Epstein, Eric Friedman, Jeff Garland, Michael Glassford, Doug Gregor, Joel de Guzman, Hubert Holin, Jaakko Jrvi, Hartmut Kaiser, Bronek Kozicki, Tarjei Knapstad, Toon Knapen, Aaron W. LaFramboise, Joaqun M Lpez Muoz, Christoph Ludwig, John Maddock, Paul Mensonides, Guillaume Melquiond, Thorsten Ottosen, Vladimir Prus, Robert Ramey, Rene Rivera, Gennadiy Rozental, Stefan Slapeta, Jonathan Turkanis, Pavel Vozenilek, Jonathan Wakely, Daryle Walker, Victor A. Wagner Jr. and Martin Wille. Also, our special thanks go to: John Maddock for the managing the effort of converting the majority of the Boost libraries to the Boost Software License, Eric Niebler and Joel de Guzman for taking on the important job of improving the Boost documentation's look and feel, and last, but not least, to our regression test runners, without whom we simply would never have released: Toon Knapen, Bronek Kozicki, Rene Rivera, Markus Schpflin, Stefan Slapeta, Victor A. Wagner Jr. and Martin Wille. Thank you everybody! -- Aleksey Gurtovoy MetaCommunications Engineering

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Iterator nesting
by Rodrigo de Salvo Braz 20 Nov '04

20 Nov '04

Hello, Suppose I have a container of containers and would like an iterator that goes through all of their elements as if they are coming from a single container. I thought I would see some Boost class helping me to do that but I couldn't find anything like that. Can someone please tell me if that is true, and if not, which class can I use to that effect? (In fact this concept is more general and interesting. The objects in the first-level containers may not be containers but have members which are containers and whose elements I want to iterate through. Or they could be iterators. The general case should allow a parameterizable way of obtaining an iterator to the elements inside the second-level objects. This could again be a nesting iterator, allowing for arbitraty nesting. Since this is a fairly common need in programming, I was expecting something that did that in Boost.) Thanks, Rodrigo

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Another weird boost::variant problem.
by Bo Peng 19 Nov '04

19 Nov '04

Dear list, I have a problem with apply_visitor of boost::variant. It seems to me that it can not accept a temporary variant variable that is returned from a function. Is this a bug? Here is a simple example: =================================== #include "boost/variant.hpp" using namespace std; #include <string> typedef boost::variant<double, string > Variable; #include <iostream> // a simple visitor that returns a variant. class variantPlusOne : public boost::static_visitor<Variable> { public: Variable operator()( double i) const { return Variable( i + 1 ); } Variable operator()( string str) const { return Variable( 0); } }; // apply_visitor in function form Variable func(Variable a) { return boost::apply_visitor( variantPlusOne(), a); } // a silly function. Variable me(Variable a) { return a; } int main() { Variable b("5"); cout << func(b) << endl; // OK cout << func(me(b)) << endl; // OK cout << boost::apply_visitor(variantPlusOne(), b ) << endl; // OK // cout << boost::apply_visitor(variantPlusOne(), me(b) ) << endl; // NO return 0; } ///////////////////////////// The error messages are: test.cpp:44: no matching function for call to `apply_visitor(variantPlusOne, Variable)' boost_1_31_0/boost/variant/detail/apply_visitor_unary.hpp:59: candidates are: Visitor::result_type boost::apply_visitor(Visitor&, Visitable&) [with Visitor = variantPlusOne, Visitable = Variable] boost_1_31_0/boost/variant/detail/apply_visitor_unary.hpp:75: Visitor::result_type boost::apply_visitor(const Visitor&, Visitable&) [with Visitor = variantPlusOne, Visitable = Variable] /////////////////////////////// Note that I can understand this behavior if the visitor takes reference arguments (and therefore expects a persistent variable) but my visitor pass argument by values. Thanks. Bo

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