August 2003 - Boost-users - lists.preview.boost.org

boost::shared_ptr and stl algorithms
by Bill Eidson 15 Apr '05

15 Apr '05

std::vector< boost::shared_ptr<T> > TVec; I want to write a function object to run std::for_each. to do somework against members of T and accumulate results in functor. My attempts have failed in VC7 with memory errors in my operator() method. struct fo { bool operator()( boost::shared_ptr<T>& t ) { return true; } }; Thanks in advance bille

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BGL and reversing / moving edges
by joshrose 17 Dec '03

17 Dec '03

G'day, I was hoping someone might be able to tell me if they've run into any situations using BGL where they needed to move (or reverse (i.e. flip the source and target)) an edge within a graph implemented as an adjacency_list. I'm working on an implementation of an algorithm for max. weight bipartite matching ("the assignment problem"), and one of the assumptions in the algorithm is that non-matched edges are directed from one subgraph, A, to the other subgraph, B, and matched edges are directed the other way. Over the course of growing the matching, a simple way to add and remove edges from the candidate set is just to reverse the edge, thus the need for some way to reverse the edge within BGL. I don't think I can just remove and then re-add the edge in the other direction, primarily because doing so will (I believe) invalidate any edge_descriptors referring to that edge. In particular, there are property maps keeping track of the weight of edges, the predecessors of certain nodes, etc. that use edge descriptors as keys. I've spent a fair bit of time reading the documentation and looking through the implementation of adjacency_lists (incl. edge_list_impl), and I'm not really sure of a way to either move an edge directly within a graph, or even to create a new edge from another s.t. they have the same edge_descriptor (in general a bad thing, probably). Anyone have any thoughts on this? Thanks, -Josh

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Bug in boost::format with 0 valued integer
by Simon Clift 15 Sep '03

15 Sep '03

Hi folks, There appears to be a bug in boost::format, an unitialized value problem spotted when I was using valgrind on a program of mine. The following test code illustrates the (admittedly minor?) problem: #include <boost/format.hpp> #include <iostream> using namespace std; int main() { int dummy = 5; cout << boost::format( "%05d" ) % dummy << endl; dummy = 0; cout << boost::format( "%05d" ) % dummy << endl; }; I compiled this with -g and when run with valgrind it seems that the put_last function in feed_args.hpp sends an uninitialized value into the standard library <<(int) operator when the integer to be printed is 0 and leading zeros are specified. Valgrind reports (clipped for size) on the second ::format call (but not the first) of the test code: ==28879== Conditional jump or move depends on uninitialised value(s) ==28879== at 0x40289470: (within /usr/lib/libstdc++.so.5.0.3) ... ==28879== by 0x4028F36B: std::ostream::operator<<(int) (in /usr/lib/libstdc++.so.5.0.3) ==28879== by 0x804CF8D: void boost::io::detail::(anonymous namespace)::put_last<char, std::char_traits<char>, int>(std::basic_ostream<char, std::char_traits<char> >&, int&) (feed_args.hpp:114) ==28879== by 0x804C9A2: _ZN5boost2io6detail31_GLOBAL__N_test00Fill.cppfx7Zjb3putIcSt11char_traitsIcERiEEvT1_RKNS1_11format_itemIT_T0_EERSbIS9_SA_SaIS9_EERSt19basic_ostringstreamIS9_SA_SE_E (feed_args.hpp:176) ==28879== by 0x804BF44: void boost::io::detail::distribute<char, std::char_traits<char>, int&>(boost::basic_format<char, std::char_traits<char> >&, int&) (feed_args.hpp:237) ==28879== by 0x804ABB6: _ZN5boost2io6detail4feedIcSt11char_traitsIcERiEERNS_12basic_formatIT_T0_EESA_T1_ (feed_args.hpp:246) ==28879== by 0x804A14B: boost::basic_format<char, std::char_traits<char> >& boost::basic_format<char, std::char_traits<char> >::operator%<int>(int&) (format_class.hpp:69) ... Hope this helps. Otherwise I'm enjoying using boost! Best regards --- Simon -- Simon Clift E-mail: ssclift at math dot uwaterloo dot ca Ph.D. Student Scientific Computation Group University of Waterloo Waterloo, Ontario, Canada N2L 3G1

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how to create fixtures in unit test framework
by Anders Moe 03 Sep '03

03 Sep '03

Hi all. The boost unit test framework seems to lack the xUnit buildUp/tearDown (whatever) methods meant to faciliate the creation of fixtures. Does that mean there is an alternative idiom to achieve the same effect ? Constructing new class-test-cases for each test seems a bit overkill. Regards, Anders.

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spirit list_p example
by Larry 02 Sep '03

02 Sep '03

From boost-1.30.2 I built the list_parser.cpp example using MSVC++7.1. In the CSV list I added ",,2" to the end of the line to be parsed. The program ran but the neither of the added elements were included in the output vector. Having used the tokenizer before I know it will generally gobble up adjacent delimiters without any output. You can get the empty token if you ask for the delimiters as well and then just discard the delimiters (sort of). But I was surprised that the 2 didn't make it to the output vector. I expected the empty list entry would not make the output vector. I tried adding ~anychar_p to the rule but that didn't help. If I change the input list to add ",\"\",2" I get "" and 2 in the output vector. Applications like spreadsheets do not put missing column values for numeric columns as "" items generally. Maybe I am missing something because it certainly isn't the behavior I would expect (either from the parser or the tokenizer).

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[BGL] Installing a property
by sashan 31 Aug '03

31 Aug '03

Hi I have a mass spring system where the particles are mapped to the vertex name property of the vertex. Now I've read (in the BGL red book) that one can install a custom property using an enumerated type. However it says that the enum must be a unique number. How do I enforce this in my code? Do I have to manually track the numbers myself? Thanks sashan [Non-text portions of this message have been removed]

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Given std::map<ID,struct>, efficient way to access std::vector<struct.member>?
by Chris Russell 31 Aug '03

31 Aug '03

Hello folks, I've got an interesting little design problem and I'm looking for some advice on how best to implement an efficient solution. [ I posted this message to comp.lang.c++.moderated yesterday. I'm reposting here because this _seems_ like a job for some type of iterator adaptor and I'm thinking that perhaps one of the Boost libraries might be useful in this context. But which (if any)? Would uBLAS help me here perhaps? Or am I way off base? ] Here's a simplified statement of the problem that I believe outlines the relevant details: I've got a class declared as follows: --- begin example class ---- class CFilter { public: typedef struct tag_sRow { A_t A; B_t B; C_t C; .. .. .. // some number of structure members... } sRow_t; typedef std::map<key_t/*type unimportant*/, sDataRow_t> mapData_t; typedef mapDataSet_t::iterator mapiterData_t; typedef mapDataSet_t::const_iterator mapconstiterData_t; private: mapData_t m_mapData; public: void ProcessRow(const sRow_t& sRow) { // process a single row of data } // end method ProcessRow void ProcessData(const mapData_t& mapData) { // algorithm needs fast access to: // std::vector<A_t>, std::vector<B_t>, std::vector<C_t> .... } // end method ProcessData }; // end class declaration CFilter --- end example class --- In English: CFilter declares some structure with some number of data members of arbitrary types. Internally CFilter allocates a std::map of these structures using some key_t. Effectively this defines a table of data whose rows are of type sRow_t, and whose columns can be conceptualized as std::vector<A_t>, std::vector<B_t> where std::vector<sRow_t.some_member>.size() == mapData<key_t, sDataRow_t>.size(). At runtime, CFilter.ProcessRow is called std::map<key_t, sRow_t>.size() times followed by a single call to CFilter.ProcessData. I'm trying to figure out how to _efficiently_ access the column vectors in the implementation of CFilter.ProcessData. Any suggestions would be greatly appreciated. Thanks in advance - Chris Russell

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Inconvenience in time_parsing.hpp - uninit variables
by Larry Knain 30 Aug '03

30 Aug '03

I was trying to use the date_time ptime functions with ISO syle input (boost 1.30.2 with MSVC++6 SP5). The function parse_undelimited_time_duration in time_parsing has three short variables hours, min, and sec that are uninitialized which lead to unpredictable results. These are at line 99. I stumbled on to this when I passed a string "20011027T0202" to ptime(from_iso_string()). To my surprise when I printed the value out it came back as 20011026T222345! The code works OK as is if you always pass a full HHMMSS. This must have been found in parse_delimited_time_duration as it has unsigned shorts that are intialized to zero.

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[BGL] adjancency iterators for property types
by sashan 30 Aug '03

30 Aug '03

Hi Is there an adjancency iterator for property types. You can get an iterator for property types like this: typedef graph_property_iter_range<GraphType, vertex_name_t>::iterator VNameIterator; .... tie(It, ItEnd) = get_property_iter_range(m_Graph, vertex_name); I'd like to know if there is something similar for adjacency iterators. Thanks -- sashan http://www.cs.auckland.ac.nz/~sgov008/

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boost::function syntax
by shyamemani 29 Aug '03

29 Aug '03

Hello everyone, I was looking at the boost::function preferable syntax. boost::funcion<float (int,int) > I also see that this has also been accepted by the standard for future STL implementation. The C++ grammar for template declaration is as stated below: template-argument-list: template-argument template-argument-list , template-argument template-argument: assignment-expression type-id id-expression None of the 'declaration' rules also seem to parse the tokens 'float (int,int) (I know I am missing something here). I could not figure out why the string 'float (int,int)' is accepted by the compiler and what type it is assigned? Is it just a extension of the standard by GCC? Can somebody help me figure this out? Thanks, Shyam

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Broken link on boost.org/libs page
by Sam Partington 29 Aug '03

29 Aug '03

http://www.boost.org/libs/hdr_depend.html Is giving a HTTP 404 error. Cheers Sam

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Re: Lambda shortcut?
by Daryle Walker 27 Aug '03

27 Aug '03

On Tuesday, August 26, 2003, at 10:05 AM, Jaakko Jarvi wrote: > In our last exciting episode Stephen Love wrote: >> operator-> *is* overloadable. > > It is, but not freely. The return type cannot be arbitrary, say a > lambda_functor type, making it not very useful for the LL. Specifically, the right side of "->" must be the NAME of a class' member or member function. It cannot be any kind of actual object (including pointers-to-member). This restricts the left side to: 1. A pointer to a (class/struct/union) data object (conventional C usage) 2. A class object with an "operator ->()" that returns a pointer to a data object 3. A class object with an "operator ->()" that returns an object that follows rules [2] or [3]. No matter what, "operator ->()" eventually leads to the standard C usage. All you can do is delay the event and build proxy objects to obtain the data. Daryle

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Link errors
by Ken Crismon 26 Aug '03

26 Aug '03

To all, I am a new user to the BOOST community and am putting together some test code to get a handle on what BOOST is and how it works. Am using .NET 2003 and am getting the following link errors. error LNK2019: unresolved external symbol "__declspec(dllimport) public: class std::_Ptrit<char,int,char *,char &,char *,char &> __thiscall std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >::end(void)" Thanks in advance for the help, Ken Crismon

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First Boost installation under Windows and Borland
by Matías Nicolás Bossa 26 Aug '03

26 Aug '03

Hello, I'm a new Boost user and I need to install it (v. 1.30.0) under Windows 2000, with Borland C++ Builder 6. I've succeed in correctly installing and using it under linux, but I couldn't install it under Windows. I downloaded and unpacked boost_1_30_0.zip. I set the following variables: BOOST_ROOT=d:\proyect\boost_1_30_0 TOOLS=borland BCCROOT=c:\archiv~1\borland\cbuilder6 PYTHON_ROOT=c:\win\python I compiled bjam.exe by running tools\build\jam_scr\build.bat, and put it somewhere in the path. (but I also tried downloading a precompiled version) I run bjam from the boost_1_30_0 directory and the following message appeared: /****************************************************/ /****************************************************/ ...found 5339 targets... ...updating 573 targets... borland-C++-action libs\python\build\bin\boost_python.dll\borland\debug\runtime-link-dynamic\numeric.obj libs\python\build\../src\numeric.cpp: Error E2401 D:\project\boost_1_30_0\boost/python/object/inheritance.hpp 69: Invalid template argument list Error E2040 D:\project\boost_1_30_0\boost/python/object/inheritance.hpp 69: Declaration terminated incorrectly Error E2231 D:\project\boost_1_30_0\boost/python/object/inheritance.hpp 130: Member cast_generator<Source,Target>::is_upcast cannot be used without an object Error E2401 D:\project\boost_1_30_0\boost/python/object/inheritance.hpp 131: Invalid template argument list Error E2040 D:\project\boost_1_30_0\boost/python/object/inheritance.hpp 132: Declaration terminated incorrectly Error E2228 D:\project\boost_1_30_0\boost/python/object/inheritance.hpp 132: Too many error or warning messages *** 6 errors in Compile *** /****************************************************/ /****************************************************/ For the moment I just need ublas and random libraries, I need boost in order to compile another library which use it, called Bayes++. I wil be very grateful if someone could help me, and I'm sorry for the length of the mail. Regards, Matías ___________________________________________________ Yahoo! Messenger - Nueva versión GRATIS Super Webcam, voz, caritas animadas, y más... http://messenger.yahoo.es

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Lambda shortcut?
by Hurd, Matthew 26 Aug '03

26 Aug '03

Hi, Is there a short cut for bind(&class::method_name, this, _1)? I could wrap it in a macro, as I use it enough, but is there something nicer I'm missing? I often just do the for loop as it is a little more readable, maybe... For example, for( some_collection::iterator i = check_list.begin(); i!= check_list.end(); ++i ) { turn_off_calcs(*i); } Is hopefully the same as for_each( check_list.begin(), check_list.end(), lambda::bind(&instrument_store::turn_off_calcs,this,lambda::_1) ); Regards, Matt.

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How to use boost::bind
by Darren Cook 26 Aug '03

26 Aug '03

Hi, I have a project with many occurences of while loops iterating through a container, and operating on the data. I'd like to use for_each() and turn them into one-liners, but I don't like writing one-off functor classes. I was hoping boost::bind could help, but I've read the docs, scratched my head, and failed to work out how the examples apply to my case. Maybe they don't and I'm trying to use it for something it cannot do? See an example below. My function currently looks something like grab_keys() and I want it to look like grab_keys2(). Could some kind soul show me how to write this? (or explain why it cannot be written). Thanks, Darren ------------------------- class Info{ public: int key; std::set<int> points; }; class InfoContainer{ public: Info* get(int); }; void grab_keys(const InfoContainer &cs,const Info *c){ std::set<int> list; std::set<int>::const_iterator i=c->points.begin(); while(i!=c->points.end()){ Info *ec=cs.get(*i++); list.add(ec->key); //Previous two lines could be written: list.add(cs.get(*i++)->key); } //Do something with list here. } void grab_keys2(const AllInfo &cs,const Info *c){ Points list; std::for_each(c->points.begin(),c->points.end(), boost::bind( /* what goes here? */ ) ); //Do something with list here. }

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newbie: comand line for g++
by Ruslan Talpa 26 Aug '03

26 Aug '03

how to staticaly link a boost library (regex) to a project (what is the g++ command line for that) Thanks PS i have only used VC till now.

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XML output from Boost test framework.
by Jarl Friis 26 Aug '03

26 Aug '03

Hi. The release notes on Boost test framework says: XML log format is introduced XML report format is introduced I would like to know how I use those features, the documentation says nothing about it, at least I can't find it. Thanks in advance. Jarl

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ClearCase and Boost
by Matt Trentini 26 Aug '03

26 Aug '03

Heya, The best way I've found to import Boost into ClearCase is by using "clearfsimport". If anyone wants a hand in setting up the parameters (it's a bit tricky - please make sure you don't use the mklabel and preview options together, otherwise you'll lock the VOB!) let me know. Cheers, Matt

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filesystem in CVS differs from 1.30.x ?
by Anders Moe 26 Aug '03

26 Aug '03

Hi all. I'm somewhat confused about how to use filesystem, since it appears that the CVS version differs from 1.30.x. In particular, the following simple snippet suddenly wouldn't compile on 1.30.2 using MSVC 7.1: boost::filesystem::path p("dd"); boost::filesystem::ofstream os("dd"); It works, however, with the current CVS version. In fact, I have failed to compile any variant of the above under 1.30.2. Regards, Anders Moe.

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mem mapping containers
by spam_me_da 25 Aug '03

25 Aug '03

I'd like to know if there is any available implementation of a memory mapped linear array. (Linux) Thanks -K

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boost::lambda how to question
by Eric Twietmeyer 25 Aug '03

25 Aug '03

Hello, I'm been having great fun getting to know and starting to use the lambda library over the past month or so. I can't believe how well the optimizing compiler I have (Vc7.1) is able to convert these lambda expressions used in for_each or find_if into tight loops. However, there I things I'm certain are possible, but I haven't been able to figure out. More examples of using the library than are found in the doc would be extremely useful. For instance, how do I do the equivalent of the following using a single for_each with suitable lambda expression as operator? using namespace boost::lambda; std::vector<int> vec1; std::vector<int> vec2; struct tOp { std::vector<int>& m_vec; tOp( std::vector<int>& vec ) : m_vec( vec ) {} void operator()( int entry ) { std::vector<int>::iterator it = std::find_if( m_vec.begin(), m_vec.end(), _1 == entry ); if ( it != m_vec.end() ) m_vec.erase( it ); } }; // How to use lambda expression here for third arg? std::for_each( vec1.begin(), vec1.end(), tOp( vec2 )); Basically, I have two lists (vectors) that overlap. I want to erase all elements from the one vector from the other vector, i.e. determine if the element from vec1 exists in vec2, and if so erase it from vec2. If this is possible and relatively straight forward using a lambda expression, I would love to see an example. Thanks in advance, Eric Twietmeyer PS It looks like something of this sort can be done with std::set_difference if one outputs into a third vector, but for argument's sake, let's assume I don't want to introduce a third vector. --------------------------------- Do you Yahoo!? Yahoo! SiteBuilder - Free, easy-to-use web site design software [Non-text portions of this message have been removed]

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boost.thread, DEC C++ (OpenVMS)
by Johan Nilsson 25 Aug '03

25 Aug '03

Hi, I've just tried to compile boost.thread under OpenVMS and got it working mostly fine, with a few quirks. I'm using Boost 1.30.2 and DEC C++ 6.5 under OpenVMS Alpha 7.1-1H1. OpenVMS provides a compliant(?) pthreads implementation. Note that I did _not_ use Boost.jam (I did try, but couldn't get it going). Compiling the .cpp files under BOOST_ROOT/libs/thread/src works pretty fine, once having defined BOOST_HAS_THREADS, BOOST_HAS_PTHREADS and BOOST_HASTIMEOFDAY on the compiler's commandline. But not for tss.cpp - I get the following error: ------------------------------------------------------------------------- res = pthread_key_create(&m_key, cleanup); .....................................^ %CXX-E-INCOMPATIBLEPRM, argument of type "void (*)(void *)" is incompatible with parameter of type "void (*)(void *) C" at line number 192 in file DISK$USER1:[COMMON.BOOST.LIBS.THREAD.SRC]TSS.CPP;1 ---------------------------------------------------------------------------- --- After some digging around I found out that the error only appears when using the compiler switch "/standard=strict_ansi", which is what I'm using all the time. Now to me it looks like the DEC C++ compiler believes that name mangling isn't the only thing that differs between "C" and "C++" linkage - does anyone here have any comments on that? See below for a small example (and possible way to work around this in the boost.thread implementation): ------ sample.cpp ------- extern "C" { typedef void (*c_linkage_cb_t)(void*); void c_linkage(void (*pfn)(void*)); } inline void cpp_linkage_using_c_typedef(c_linkage_cb_t pfn) { c_linkage(pfn); } inline void cpp_linkage(void (*pfn)(void*)) { c_linkage(pfn); } ---------------- end sample.cpp ------------------- And here's the output from the compiler: $ cxx /standard=strict_ansi t.cpp c_linkage(pfn); ..................^ %CXX-E-INCOMPATIBLEPRM, argument of type "void (*)(void *)" is incompatible with parameter of type "void (*)(void *) C" at line number 19 in file DISK$USER1:[COMMON.BOOST.LIBS.THREAD.SRC]T.CPP;11 I don't know if this is a compiler bug or not, but in order to work around this in boost.thread, wouldn't it be feasible to provide a similar fix to the tss implementation to avoid the compilation problem - e.g. ---- tss.hpp ----- ... extern "C" { typedef int (*pthread_<something>_cb_t)(void*); } ... class tss { ... ... tss(pthread_<something>_cb_t cb) ... --- end tss.hpp ---- Comments appreciated // Johan

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out of core property map and constant property map
by Joel Young 24 Aug '03

24 Aug '03

Has anyone created property maps that operate out of core? either against a database or a flat file? Would you like to share? Also has anyone created a property map that, once create returns a constant value for all queries (writable is nice, it doesn't do anything with the write of course)? This might be useful for compactly representing constant edge capacities. Finally, an out of core BasicMatrixConcept implementation for use with all-pairs shortest path on largish (n=1.6M, e=10*n) graphs would be handy. Thanks, Joel

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graph adapter from bidirectional to undirected
by Joel Young 24 Aug '03

24 Aug '03

Has anyone created a graph adapter to make a bidirectional graph appear as an undirected graph? If not, is the difficulty in making an edge iterator across both the in and out links? I particular I would like to compute a weak connected components on a bidirectional graph. So if you have a modified connected components alg for that it would be great. Thanks, Joel

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