January 2002 - Boost-users - lists.boost.org

graph: depth first search
by tobi_schuele 15 Jan '02

15 Jan '02

Hi, I'd like to use depth_first_search to check whether a particular vertex is reachable from the root vertex. Is there a way to stop the search when the vertex is found? In other words, can a visitor be used to cut the search tree? Sorry, if this is a newbie question. Thank you very much in advance for your help. Tobias

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[newbie] segmentation fault on running dijkstra example on RedHat 7.2
by Mohammad M. Purbo 15 Jan '02

15 Jan '02

Dear All, I'm new to BOOST. I tried to compile the [BOOST_HOME/libs/graph/example/dijkstra-example.cpp] provided on the distribution with the following comand: gcc -I/home/purbo/include -lstdc++-3-libc6.2-2-2.10.0 -o dijkstra-example dijkstra-example.cpp no error on compiling/linking, but when i ran it, i got: Segmentation fault I used: RedHat 7.2 gcc 2.96 Anybody knows the problem? Thank you in advance, M. Purbo

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A Static Map?
by Duane Murphy 14 Jan '02

14 Jan '02

I have learned a lot about templates and library programming from reading and using the Boost code. Recently I have been finding myself doing something that I would call Static Maps. Basically I would like to use an array of structs as if it were a map or associative array. Does boost have anything like this or can anyone recommend something like that? Here is a simple example: struct entry { const char* key; const char* value; }; const entry entries[] = { { "one", "Hello" }, { "two", "World" }, { "three", "!" } }; { some_type the_map = make_static_map( entries ); const char* word = the_map[ "one" ]; } This is a real poor example, but shows the idea. The struct could be any types that are less-than comparable; maybe there is some special arrangment of key and type. But the idea is there. I would like to be able to lookup items in a static array of items using array notation (other than numerically indexed). For extra credit, the interface would be writeable also; aka a fixed array space map. Any idea? Comments? Suggestions? ..Duane

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Any interest in a weak pointer?
by wayneconrad 14 Jan '02

14 Jan '02

Is there any interest in a weak pointer that plays well with shared_ptr and its friends? Wayne Conrad

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RE: [Boost-Users] Any interest for a parser class?
by Bjorn Karlsson 14 Jan '02

14 Jan '02

> From: Patrick Guio [mailto:patrick.guio@fys.uio.no] > > > Dear all, > I have written a parser class and I wanted to know whether it > could be of > any interest to be included in the boost system. Here is a > short description > of it. > This class is meant to be used in two ways, either to be > included in another > class as an inherited class and/or to be included in the main routine. > [snip] > > This is brief example to show how the class Parser can be used. > it can be used to handle more complex inherited classes. > If it can be of any interest, let me know and I will provide > you with more > details. > > Sincerely, > Patrick > I suggest that you also post this message to the Boost mailing list (http://groups.yahoo.com/group/Boost/) While Boost-Users certainly is a good place to get insightful opinions and reflections, the focus is to handle issues related to using existing Boost libraries. Also, library submissions and reviews are performed by the Boost list, so you'll need to go there sooner or later. Regards, Bjorn [Non-text portions of this message have been removed]

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Any interest for a parser class?
by Patrick Guio 14 Jan '02

14 Jan '02

Dear all, I have written a parser class and I wanted to know whether it could be of any interest to be included in the boost system. Here is a short description of it. This class is meant to be used in two ways, either to be included in another class as an inherited class and/or to be included in the main routine. The first use is for classes containing fields to be initialised with some values. So far it handles intrinsic C++ types and STL vectors of intrinsics. As an example, the class Parser can be used in the class Foo as class Foo : public Parser { Foo::Foo(int nargs, char *args[]); private: enum { var1_enum, ... }; int var1; .... }; The Foo constructor that uses the Parser feature looks like Foo::Foo(nargs, args, ....) : Parser(nargs, args), var1(default_var1), ... { // Register class Parser::RegisterClass("Foo"); Parser::RegisterPackage(package, version, copyright); // Insert options and aliases to parse a value to var1 // the Any constructor is used to register the default value Parser::InsertOption(var1_enum,"var1","var1_type","var1_comment", Any(var1)); // Insert alias to option Parser::InsertOptionAlias(var1_enum, "var1_alias1"); Parser::InsertOptionAlias(var1_enum, "var1_alias2"); .... // Possibility to add a "debug level option" that takes an int argument, // the default value is 0 Parser::ParseLevelDebugOption("debug_level_option_name"); // the member function int Parser::DebugLevel() can be used thereafter to // check the this value if (Parser::DebugLevel() > 50) cout << "Debug level is " << Parser::DebugLevel() << endl; } Then a member function Foo::ParseParameters() method could look like void Foo::ParseParameters() { // The ParseOption family member functions return a boolean indicated // whether the var1 has been parsed if (Parser::ParseOption(var1_enum,var1)) cout << "var1 = " << var1 << " parsed." << endl; // Other ParseOption member functions are // * Parser::ParseOption(var1_enum,var1,"filename") // parse the filename "filename" instead of the command line // * Parser::ParseOptioninFileonCmdLine(var1_enum,var1) // if the option -i/--input[=]paramter_file is on the command line then // parse first the parameter_file, thereafter the command line. // * Parser::ParseOptiononCmdLineinFile(var1_enum,var1) // if the option -i/--input[=]paramter_file is on the command line then // parse first the command line, thereafter the parameter_file // * Parser::ParseHelp() // if the option -h/--help is parsed, print to standard output a message // with class_name information and a list of all the registered/inserted // options for that class in the predefined format : // option_name[,option_aliases] option_type option_comment // and return a true boolean // * Parser::ParseVersion() // if the option -v/--version is parsed, print to standard output a // message containing information package, version, copyright for the class // * Parser::ParseTemplate() // if the option --create-template is parsed, print to standard output a // message with class_name information and a list of all the // registered/inserted options for that class in a format to be used // later with the -i/--input containing information about variable and // aliases, type of the variable, comment/description and default value } The second way of using is from the main routine and is very similar to the first way int main(int nargs, char *args[]) { try { Parser parser(nargs, args); parser.RegisterProgram(args[0]); parser.RegisterPackage(package, version, copyright); Foo foo(nargs, args); // Insert options if necessary ... // Parse defaults if (parser.ParseHelp()) { foo.ParseHelp(); return EXIT_SUCCESS; } if (parser.ParseVersion()) { foo.ParseVersion(); return EXIT_SUCCESS; } if (parser.ParseTemplate()) { foo.ParseTemplate(); return EXIT_SUCCESS; } // Parse option for program if necessary ... // Parse class option foo.ParseParameters(); ... return EXIT_SUCCESS; } catch(ParseException &x) { cerr << x.what() << endl; return EXIT_FAILURE; } } The try/catch is used to handle potential errors at parsing and uses a class ParseException. This is brief example to show how the class Parser can be used. it can be used to handle more complex inherited classes. If it can be of any interest, let me know and I will provide you with more details. Sincerely, Patrick ====================================================================== Patrick Guio Institute of Physics, University of Oslo P.O. box 1048, Blindern, N-0316 Oslo Tel : (+47) 22 84 40 60 - Fax : (+47) 22 85 56 71 E-mail : patrick.guio(a)fys.uio.no URL : http://folk.uio.no/~patricg

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iterator_adaptors Comment
by Duane Murphy 14 Jan '02

14 Jan '02

There is a comment in iterator_adaptors: public: // implementation details (too many compilers have trouble when these are private). Policies& policies() { return m_iter_p.second(); } const Policies& policies() const { return m_iter_p.second(); } Base& iter() { return m_iter_p.first(); } const Base& iter() const { return m_iter_p.first(); } This seems to imply that iter() and policies() ought to be private. I would like to suggest that having access to the underlying iterator is valuable. This is especially true of transform and projection iterators which allow you to locate a record by searching on a field. Access to the underlying iterator gets access to the rest of the record. Is there some other way of accomplishing the same thing without using iter()? Thanks, ...Duane

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iterator_adaptor const iterator question
by Duane Murphy 14 Jan '02

14 Jan '02

I have now built a couple of iterators using boost::iterator_adaptor. These are not adapted iterators but rather iterators developed to iterate over interfaces that have not iterators. I havent found a good example of how to declare the equivalent of a const_iterator like in vector. What would the declartion look like? If the definition of an iterator is: typedef boost::iterator_adaptor< Base, Policy > iterator; What would the declartion for a const_iterator look like? Thanks for the help. ..Duane

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[newbie]compiling 'regex_split example: split a string into tokens' failed
by pr275116 11 Jan '02

11 Jan '02

Hello, compiling the 'regex_split example: split a string into tokens' failed with an 'undefined symbols' message (see below). I am using Project Builder 1.1.1 the following compiler: Apple Computer, Inc. version gcc-934.3, based on gcc version 2.95.2 19991024 (release) on MacOSX 10.1.2 (Unix BSD 4.4). Any help would be much appreciated. Philippe de Rochambeau /usr/bin/jam -d1 JAMBASE=/Developer/Makefiles/pbx_jamfiles/ProjectBuilderJam base JAMFILE=- build ACTION=build TARGETNAME=Boost2 NATIVE_ARCH=ppc BUILD_STYLE=Development CPP_HEADERMAP_FILE=/Users/philippe/Documents/Projets_ ProjectBuilder/Boost2/build/intermediates/Boost2.build/Header maps/Boost2.hmap DSTROOT=/ OBJROOT=/Users/philippe/Documents/Projets_ProjectBuilder/B oost2/build/intermediates SRCROOT=/Users/philippe/Documents/Projets_ProjectBuilder/ Boost2 SYMROOT=/Users/philippe/Documents/Projets_ProjectBuilder/ Boost2/build ...updating 9 target(s)... BuildPhase Boost2 Completed phase <CopyHeaders> for Boost2 CompileCplusplus /Users/philippe/Documents/Projets_ProjectBuilder/Boost2/build/ intermediates/Boost2.build/Objects/ppc/main.o BuildPhase Boost2 Completed phase <DeriveAndCompileSources> for Boost2 MasterObjectFile.Combine /Users/philippe/Documents/Projets_ProjectBuilder/Boost2/build/ intermediates/Boost2.build/master.o StandaloneExecutable /Users/philippe/Documents/Projets_ProjectBuilder/Boost2/build/ Boost2 /usr/bin/ld: warning prebinding disabled because of undefined symbols /usr/bin/ld: Undefined symbols: __._Q25boost11bad_pattern __._Q25boost14bad_expression __Q35boost9re_detail13c_traits_base.class_map __Q35boost9re_detail13c_traits_base.lower_case_map __Q35boost9re_detail13c_traits_base.syntax_map ___Q25boost14bad_expressionRCt12basic_string3ZcZt18strin g_char_traits1ZcZt24__default_alloc_template2b0i0 ___Q25boost7regbase ___vt_Q25boost11bad_pattern ___vt_Q25boost14bad_expression _do_lookup_class__Q35boost9re_detail13c_traits_basePCc _do_lookup_collate__Q35boost9re_detail13c_traits_baseRt12 basic_string3ZcZt18string_char_traits1ZcZt24__default_alloc_t emplate2b0i0PCc _error_string__Q35boost9re_detail13c_traits_baseUi _init__Q25boostt14c_regex_traits1Zc _m_free__Q25boostt14c_regex_traits1Zc _toi__Q25boostt14c_regex_traits1ZcRPCcPCci _toi__Q25boostt14c_regex_traits1Zcc _transform__Q25boostt14c_regex_traits1ZcRt12basic_string3Z cZt18string_char_traits1ZcZt24__default_alloc_template2b0i0R CB1 _transform_primary__Q25boostt14c_regex_traits1ZcRt12basic _string3ZcZt18string_char_traits1ZcZt24__default_alloc_templa te2b0i0RCB1 _update__Q25boostt14c_regex_traits1Zc /usr/bin/cc -o "/Users/philippe/Documents/Projets_ProjectBuilder/Boost2/buil d/Boost2" "-L/Users/philippe/Documents/Projets_ProjectBuilder/Boost2/bu ild" "-F/Users/philippe/Documents/Projets_ProjectBuilder/Boost2/bu ild" -filelist "/Users/philippe/Documents/Projets_ProjectBuilder/Boost2/buil d/intermediates/Boost2.build/Objects/LinkFileList" "-arch" "ppc" "-prebind" "-lstdc++" ...failed StandaloneExecutable.LinkUsingFileList /Users/philippe/Documents/Projets_ProjectBuilder/Boost2/build/Boost2 ...

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tuple I/O trouble
by s1imshady86 11 Jan '02

11 Jan '02

When my test program gets to the cout << a; line i get a external error. As far as i can tell the library is setup right. I had no problem using tuples in other programs but cant seem to print them. The documentation doesn't list this feature as broken on my compiler or any compiler for that matter. Im using MSVSC++ btw. #include <iostream> #include <boost/tuple/tuple_io.hpp> using namespace std; using namespace boost; int main () { tuple<int,int> a (23,42); cout << a; return 0; } heres the error verbatim: --------------------Configuration: Tuple - Win32 Debug---------------- ---- Compiling... Test.cpp Linking... Test.obj : error LNK2001: unresolved external symbol "private: static int const * const boost::tuples::detail::format_info::stream_index" (?stream_index@format_info@detail@tuples@boost@@0QBHB) Debug/Tuple.exe : fatal error LNK1120: 1 unresolved externals Error executing link.exe. Creating browse info file... Tuple.exe - 2 error(s), 0 warning(s)

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