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

RE: [Boost-Users] Subject: Poll results for Boost-Users
by Jim.Hyslop 24 Jan '02

24 Jan '02

Tom Matelich [SMTP:tmatelich@zetec.com] wrote: > I asked the original question that sparked this, and its because (at the > root) I want to know whether feature requests need to be mirrored on the > main boost list. So if I can be sure that the author of the library is at > least listening to my boost-users message, I don't have to CC him/her or > spam both lists. The moderators have agreed that one of our duties will be to ensure appropriate cross-pollination of messages. In other words, if a discussion here in Boost-Users raises an issue that is appropriate to the main Boost list (such as a feature request or a bug report), we will ensure it gets forwarded to that forum. Similarly, if someone posts a message to Boost that is more appropriate to this list, we will encourage the original poster to switch to this forum. -- Jim

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Adding edges to a graph. Problems.
by lucatoldo 24 Jan '02

24 Jan '02

I think there is something I do not know, rather important, about the process of adding edges to the graph object. Infact, even in the simple libs/graph/example/bfs.cpp if I swap the start with the ends, I get different results. Namely: If I change the code from this boost::add_edge(0,2,G); boost::add_edge(1,1,G); boost::add_edge(3,1,G); ... boost::add_edge(4,1,G); to boost::add_edge(2,0,G); boost::add_edge(1,1,G); boost::add_edge(1,3,G); ... boost::add_edge(1,4,G); then I get the graph OK but the distances and the parent vectors are screwed: I get distances: 0 2 2 2 1 instead of distances: 0 2 1 2 2 and parent[0] = 0 parent[1] = 4 parent[2] = 4 parent[3] = 4 parent[4] = 0 instead of parent[0] = 0 parent[1] = 2 parent[2] = 0 parent[3] = 2 parent[4] = 2 I feel I am missing some basic knowledge on how to appropriately use this powerful and amazingly fast system. I would love to learn the missing bit. Looking forward your advice and sorry again for the dumminess of this question.

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A tip from the Dr.
by jackthompson99 23 Jan '02

23 Jan '02

Hey guys, I sent an e-mail to Dr. Stroustrup a couple nights ago, and he replied, "Have a look at boost.org. They exist specifically to provide better libraries in the context of the C++ standard library and to act as a test bed for new library ideas". So, here I am. I've installed and built my boost libraries, and I'm trying to figure out how to dig in. Anyway, here's what I was telling the Dr. I've been using C for about a decade, and C++ for about 7 yrs. I'm a huge fan of your invention, and I honestly feel like your name should eventually be as well known as Tesla and Edison. And the Standard Template Library is an incredibly well engineered system. I have a way to use it that is generic enough that it may be a candidate to be another standard. I know that's a lot to say. I'd like to explain it briefly, but first I should explain why I find it useful. Since I started working with assembler, I've always felt like the language I was using was missing something. I've used an assortment of languages, and it seems like they are all missing the same thing. The main part isn't really missing from C++, it's just not commonly understood. The concept of virtual construction is the core of the issue. Now I know that this problem is solved, but it really could stand for just one more thing to wrap it up into something usable for any ordinary C++ developer. Using a virtual constructor by way of a template, a developer can easily create any kind of object based on any type of identifier, but what good is that when the developer has exhausted all of his efforts on just building a simple system to dynamically create objects. The developer needs a way to organize these objects, without building another data warehouse. And I have never heard of a complicated database that shouldn't be fully hierarchical. So, the system should be one hundred percent re-entrant. Well, I have such a beast. I'm not done with it yet. I'm just now finishing up a project for Textron, where some of this concept was cultivated into my skill set. I am having a rough time explaining the system to my boss, and I'm in a real bind, but that's another story. The main thing that I've learned from this job is that the world needs to come together on one simple international standard for dealing with data and persistent C++ objects. I've used my ClassFactory / DataStore system as a foundation for another library that I call the WinFactory. This system simply uses the ClassFactory / DataStore as a database manager. The objects held in the database are simply graphical user interface components. This worked out really well, `till by boss took it apart. But I have a version of it that I'm re-writing at home that is much better. The database can be held either in a simple text format, resembling hypertext, or a binary file. The system relies heavily on the memory manager, so fast memory allocation is required. I have also populated an MFC user interface with data held in these objects. The system seems to be able to flex with just about anything, and I feel like it could at least contribute to discussions about new standards that are based on your standards. By the way, I need to find a team that I can work with who has good work ethics and integrity. Suggestions would be much appreciated. ..... So, I've looked at the library list in Boost, and haven't recognized anything like what I've built. I would love to explain this system. But, again, this one belongs to Textron, and all of the documentation too. I need to find some time to build this system for Boost.org. The main concept behind the system is a warehouse environment. The warehouse hase isles of goods. Each isle is any length, and each isle contains exactly one type of product. And every product contains a single pointer which is initally NULL. This makes it so that when you pull the product off the shelf and open it, you will see whatever the product is ( characters, integers, strings, etc. ), and you will find one more thing. It's called the nest. Now, until you try to use the nest, it's empty (NULL). But when you need it, it is created. What is this nest you ask? It's another warehouse. Just like the one that it is contained within. So, the entier concept is one hundred percent re-entrant. This makes it easy to build hierarchical infrastructures. The objects can be virtually any C++ thing. They persist with the greatest of ease to simple IO objects. User interfaces are easy to build with this system. Content editors view it as a script. C++ programmers view the script as C++ objects. Again, I need to finish re-writing the system, and I need to document it. But I feel like it is a candidate to become another Boost library. What do you think?????

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RE: [Boost-Users] Subject: Poll results for Boost-Users
by Jim.Hyslop 23 Jan '02

23 Jan '02

Chris Little [SMTP:clittle@renlearn.ca] wrote: > When the question first came up of allowing members to view the membership > list, one of the moderators started a poll (around the beginning of > January). That'd be me. > Unfortunately polling in this group is limited to moderators. > The moderators then decided to discuss the issue amongst themselves and they > haven't reported back. Hoo, boy, I seem to have dropped the ball on several counts here. First, my apologies for not cancelling the poll after discovering polling was limited to moderators. Second, my apologies for not reporting back to the group on the results of our discussion (I'm taking responsibility for this, since I'm the one who opened the can of worms in the first place). We identified a potential problem with spam email harvesting. Granted, in the public pages emails are hidden, so that only the first letter of the domain appears (my address, for example, would appear as "jim.hyslop@l..." One of the moderators pointed out: > About half of the email addresses on > the first page start with either an a, h, or y. > ... the problem is that when harvesting email addresses you > don't need 100% accuracy. Just assume that a's are aol, all b's are > bigfoot, all e's are earthlink, all h's are hotmail.com, and all y's > are yahoo.com. These letters are going to be [greater than] half the list and you > will be correct [greater than] half the time. We could not come up with any compelling arguments in favour of opening the list. I believe the best summary was: > I'm not sure what the benefits of public membership would be. > Arguments such as "I need to know if X is a member of > the group" seem empty - this is a *mailing list* after all. > To access individuals, you should get hold of them in > other ways. If they are active members of the list, you'll > still know they're members. No moderators actually spoke out in favour of opening the list up, so the status quo remains. We moderators are, of course, open to suggestions, and if a reasonably strong argument comes up, then we will re-examine the issue. If anyone feels strongly about it, you can either post your rationale here or email the moderators at boost-users-owner(a)yahoogroups.com (the 'boost-users-owner' name is a bit misleading - email goes to all moderators, not just to the owner). Similarly, on the topic of polls themselves, the general consensus was that if or when we identify a good reason to run a poll, then we will open up the feature. Until then, there's no reason to change the status quo. -- Jim

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RE: [Boost-Users] Subject: Poll results for Boost-Users
by Chris Little 23 Jan '02

23 Jan '02

When the question first came up of allowing members to view the membership list, one of the moderators started a poll (around the beginning of January). Unfortunately polling in this group is limited to moderators. The moderators then decided to discuss the issue amongst themselves and they haven't reported back. Chris > -----Original Message----- > From: James Curran/MVP [mailto:jamescurran@mvps.org] > Sent: Wednesday, January 23, 2002 8:29 AM > To: Boost-Users(a)yahoogroups.com > Subject: RE: [Boost-Users] Subject: Poll results for Boost-Users > > > How long was that poll open for? > > Truth, > James Curran > > > -----Original Message----- > From: Boost-Users(a)yahoogroups.com > [mailto:Boost-Users@yahoogroups.com] > Subject: Poll results > for Boost-Users > > > The following Boost-Users poll is now closed. Here are the > final results: > > > CHOICES AND RESULTS > - I want only the moderators to be able to view the > membership list, 0 votes, 0.00% > - I want anyone to be able to view the membership list, 0 > votes, 0.00% > [Non-text portions of this message have been removed]

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RE: [Boost-Users] Subject: Poll results for Boost-Users
by James Curran/MVP 23 Jan '02

23 Jan '02

How long was that poll open for? Truth, James Curran -----Original Message----- From: Boost-Users(a)yahoogroups.com [mailto:Boost-Users@yahoogroups.com] Subject: Poll results for Boost-Users The following Boost-Users poll is now closed. Here are the final results: CHOICES AND RESULTS - I want only the moderators to be able to view the membership list, 0 votes, 0.00% - I want anyone to be able to view the membership list, 0 votes, 0.00%

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Ann: Forward lookahead asserts now supported by regex lib
by John Maddock 23 Jan '02

23 Jan '02

The regex lib, now has experimental support for perl style forward lookahead assertions, using the syntax extensions: (?=exp) positive zero width forward assertion on exp. (?!exp) negative zero width forward assertion on exp. I'm currently looking for anyone willing to test these, and for real world test cases to add to the regression tests, before documenting the extensions and making them "official". Many thanks. - John Maddock http://ourworld.compuserve.com/homepages/john_maddock/

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error with thread.hpp
by thrashmodule 19 Jan '02

19 Jan '02

I got this message: c:\boost_1_26_0\boost\thread\thread.hpp(17) : fatal error C1189: #error : Thread support is unavailable! I use VC++ on Win98 so now what??????????

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Class destructor invocation - possible by hand?
by Jonathan Brownell 19 Jan '02

19 Jan '02

I have a question for all you C++ gurus. I'm writing a class that I would like to use the following technique in, and I'm not sure if it's portable or even legal, although VC++6 and VC++.NET, which I'm compiling in, work beautifully with it. Consider the following class, a very simplified example that I wrote to demonstrate: class House { public: explicit House(const int rooms) : m_rooms(rooms) { } ~House() { } private: const int m_rooms; }; Pretty straightforward. I'd like m_rooms to remain const to protect it from accidental modification by member functions, since it will *never* be changed during operation. Now, the first problem that arises is that this is illegal: House housingComplex[100]; Because, obviously, the constructor requires that the number of rooms be passed to it. (Yes, we could create it as an array of House pointers and create them dynamically, but in my case that will require inconveniences by everybody using my class.) So, we make it a default parameter and add an assignment operator: class House { public: explicit House(const int rooms = -1) : m_rooms(rooms) { } ~House() { } House& operator =(const House& source); private: const int m_rooms; }; When rooms == -1, the House is considered to be uninitialized. Now, we can do the following: House housingComplex[100]; housingComplex[0] = House(5); housingComplex[1] = House(4); (etc) The question is, how to implement the assignment operator? This is my method: House& House::operator =(const House& source) { assert(m_rooms == -1); this->~House(); new(this) House(source); return *this; } Yikes! I know this looks weird. First, assert verifies in debug mode that the object is in its uninitialized state. Then, the destructor is called manually to destruct the class and its contents. (In the actual class I'm working on, there are numerous member variables that must be appropriately destructed, and all of them are - I've checked.) Simply calling ~House(); will not compile, because the compiler assumes I'm trying to use the ~ operator illegally, so I have to call it through the 'this' pointer. Then, the placement new operator is used to create a new House in exactly the same space in memory as the old one, using the default copy constructor so that all the const variables are (re)initialized. Finally, a technicality for all assignment operators, a reference to the object is returned. (This is so C-style expressions like "var1 = var2 = var3 = 5;" can be used.) Now, this works beautifully on my VC++. But... is it legal C++?? Am I entering the realm of "undefined behavior", or is this a perfectly legitimate technique? Is there an obviously better solution to my problem? Are there caveats that I should be looking out for? Please, someone with more knowledge of the C++ standards, give me a hand here. Thanks! -Jonathan

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RE: [Boost-Users] Class destructor invocation - possible by hand ?
by Tom Matelich 17 Jan '02

17 Jan '02

> > > > Also, I would recommend that you either reconsider > > > having the constant member variable, or use a > > > vector<>. > > > > Using a vector<T> won't work in this case, because the STL uses > > T::operator = in order to copy vector contents into new > locations during > > memory reallocation. And there's no logical way to > implement operator = > > when a const data member is present, which is the cause of this > > conversation. > > I could use std::list, since it doesn't do reallocation, but clients > > using this class in containers will most likely need random access > > iterators. > > > > Any other ideas? > > Easy option: Use a vector<shared_ptr<T> >. This will give you > basically > the behavior you want, with the ability to initialize the elements > directly. The drawback is that the data will be dynamically allocated. Another drawback is the interface is now pointers, not references. If you don't mind the dynamic allocation, the vector<shared_ptr<T> > can be contained by another class, overloading operator[], etc. The Boost Iterator Adapter library works very nicely for providing vector<T>::iterator behavior from a vector<shared_ptr<T> >::iterator. I can send you our vector-like class which uses adapted iterators if you would like. Re: the moderation. Yes, this is not a boost question, but it is a question boost can provide good solutions for, so where do you draw the line?

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regex_match doesn't match in an embedded string
by soleani 17 Jan '02

17 Jan '02

Hi there, not sure how I could write that Subject line. Sorry :-) Here's the thing, I have a file with the following: KEY1 = ${short_localhost} KEY2 = bbbf<control2.cfg:OTHER_SECTION:${long_localhost}>aaaf:<he I need to extract the value between the {} when it starts with a $. My expression works ok for KEY1 (the value part, the string to the right of the equal sign), however it doesn't match for the value for KEY2. This is what I have: static const boost::regex expression( "\\$\\{(.*?)\\}" ); boost::cmatch what; if ( boost::regex_match( input, what, expression ) ) { cerr << "GOT IT!" << endl; } else { cerr << "NOPE" << endl; } where input is a std::string with the value described above. Why does it work for KEY1 and not KEY2? Interestingly enough, if I do the following: KEY1 = dd${short_localhost} it doesn't match either. This same expression in Perl works fine though. thanks, -Anibal

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RE: [Boost-Users] boost tokenizer
by Jim.Hyslop 17 Jan '02

17 Jan '02

Peter Dimov [SMTP:pdimov@mmltd.net] wrote: > From: "hicks" <hicks(a)kgk.co.jp> > > Do you know why the compiler places precedence on that interpretation, > > rather than on one giving an instatiation of a local variable? > > The C++ standard says that a function declaration takes precedence. Don't > ask me why. :-) (At the risk of sliding seriously off topic...) I suspect it's something along these lines. Given this function: void f() { int WhatIsThis(); } Is "WhatIsThis" intended to be a declaration of a function, or is it intended to be a definition and default-initialization of an int variable? A C++ compiler cannot know, so the C++Standards committee had several choices: 1) require the compiler to flag the statement as an ambiguous statement 2) require the compiler to interpret the statement as a declaration of a function 3) require the compiler to interpret the statement as a definition of an int If we examine the same syntax in C, there is no question what it is: 'WhatIsThis' is a declaration of a function. That effectively eliminates #3 from consideration because you don't want one statement to have different meanings in C and in C++. I suspect the Committee then either flipped a coin (or some used other democratic means, such as debating and voting on the issue, thumb-wrestling, or playing paper-rock-scissors) to decide between #1 and #2, or choose to adapt the well-worn guideline "When in doubt, do as the ints do" to "When in doubt, do as C does". -- Jim

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boost tokenizer
by hicks 17 Jan '02

17 Jan '02

Dear boost users I am trying to use the boost tokenizer with Borland Builder C++ 5 compiler. This far compiles fine: boost::tokenizer<> tok(std::string(ac0)); All further references to tok such as tok.assign(std::string(ac0)) or tok.begin() result in an error message " Structure requires on the left side of . or .*" Any advice would be welcome. Craig Hicks Engineer, KGK, Tokyo Japan

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Boost Array Question
by Duane Murphy 16 Jan '02

16 Jan '02

Below is a simple example that I cannot get to compile. I would like to create a subclass of boost::array in order to give it some additional functionality (I would like a associative array like interface). When I compile this, I get an "illegal initialization" error for test. I am using Metrowerks Codewarrior 7 on Mac OS X. Is there some special incantation required? I suspect that I am in some kind of specialized area and I cant get there from here. template < class T, std::size_t N > struct test_array : public boost::array< T, N > { }; static boost::array< char,1 > array_test = {{ 'a' }}; static test_array< char, 1 > test = {{ 'a' }}; It appears that if I aggregate instead of inherit that this might work (at least it compiles :-) template < class T, std::size_t N > struct test_array { boost::array< T, N > array_; }; static boost::array< char,1 > array_test = {{ 'a' }}; static test_array< char, 1 > test = {{ 'a' }}; // The funny thing is this works also: static test_array< char, 1 > test2 = { 'a' }; TIA, ...Duane

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tokenizer
by rradh 16 Jan '02

16 Jan '02

Hi, I have string line("a_1 = b_1 ( c_2 )") tokenizer< > tok(line); for (tokenizer<>::iterator beg=tok.begin(); beg!=tok.end();++beg) { cout << *beg << endl; } gives me a 1 b 1 c 2 I want to be able to specify delimiters like in strtok so that I get a_1, b_1 and c_2 but couldn't figure out how to specify the tokenizer function. Any suggestions? Regards Rajesh

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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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