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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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