November 2004 - Boost - lists.preview.boost.org

[filesystem] Major changes before standardization
by Beman Dawes 13 Feb '05

13 Feb '05

I'm currently working on a major revision of the Boost filesystem library aimed at getting it ready to be proposed to the C++ committee for the next Library TR. The critical technical change required is internationalization. The plan is to provide a templated basic_path class, with typedefs for path and wpath. In other words, an approach very similar to the current std::basic_string, std::string, and std::wstring. Doing this adds a certain amount of complexity compared to the current path class. For example, a path_traits class has to be introduced to give basic_paths on user defined types a way to import the conversions, delimiters, and other traits. To offset the added complexity, I'd like to reduce some of the complexities in the current design: * Eliminate the distinction between native and generic grammars; either would be permitted in all contexts. As well as simplifying the class interface a bit, this will also eliminate a source of user confusion. * Move the name error checking from the basic_path class into stand alone functions. Although the current error checking could be further improved by Peter Dimov's suggested change allowing failure to be treated as either a warning or a hard error, moving it out of the class simplifies the interface, allows full path (rather than name-by-name) error checks, and eases internationalization. The primary downside of these changes will be that users who want path portability checks will have to code calls to checking functions that are currently being called automatically. The internationalization of the library is a big enough change that we will probably want to have at least a mini-review once the changes are complete. Comments? --Beman

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StringAlgo::split issue
by Dirk Gregorius 29 Jan '05

29 Jan '05

Hi, I used the split function on the following string: vector<string> tokens; string str= "( 448 448 64 ) ( 448 0 64 ) ( 0 448 64 ) name 0 0 0 0.5 0.5 0 0 0"; split( tokens, str, is_any_of( ()), token_compress_on ); // I pass 'space' , '(' and ')' into is_any_of() I was supposed to get 18 tokens. The first nine values, the string "name" and the remaining eight digits. "split" always returns a string vector containing 19 tokens, where the first element of the vector is an empty string. Why does the function insert empty strings into the collection? Can I use split to obtain the 18 wanted tokens? -Dirk

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typeof integrated
by Arkadiy Vertleyb 10 Dec '04

10 Dec '04

Hi all, Peder and I have put together a combined version of our typeof implementations. The integrated library supports both compliant and vintage compilers, and can be found in the Boost sandbox CVS (boost/typeof, libs/typeof) or at: http://groups.yahoo.com/group/boost/files/typeof_integrated.zip As always, any comments are most welcome. Regards, Arkadiy

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Name checking in filesystem
by Walter Landry 08 Dec '04

08 Dec '04

Greetings, I have come across an annoying problem with the filesystem library. I have wrapped filesystem with Swig so that I can call it from python. I had to rewrite the filesystem::path implementation a little because Swig can't handle nested classes. In any case, once I got that sorted out, I wanted to do something like p=path(".bar") which doesn't work because filenames starting with a period are not allowed by the default name checking routine. Argh. Unfortunately, I can't figure out how to change the default name checker from python. If I worked at it long enough, I could probably work it out. But I am sure that I don't want to have to run something like path.default_name_check(no_check) at the beginning of every 10 line script. It is a particular piece of functionality (name checking) that just gets in the way. I would wager that most people using boost::filesystem from scripts would not want to have to deal with it, since it is completely different from every other portable, cross platform filesystem API. So to make a long story short, I think the default for boost::filesystem should be not to check for "portable" paths. This is different from a position I took earlier, where I thought that it is ok if I only have to set it once at the beginning. That is acceptable for large programs, but not for small ones. Regards, Walter Landry wlandry(a)ucsd.edu

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duplicate source files in boost- utf8_codecvt_facet
by Robert Ramey 07 Dec '04

07 Dec '04

We now have a at least one set of files more or less duplicated in boost. Ron Garcia's utf8_codecvt_facet is included in: boost/utf8_codecvt_facet.hpp boost/detail/utf8_codecvt_facet.hpp boost/libs/serialization/src/utf8_codecvt_facet.cpp boost/libs/program_options/detail/utf8_codecvt_facet.cpp boost/libs/doc/serialization/utf8_codecvt_facet.html boost/libs/serialization/test/test_utf8_codecvt_facet.cpp Leaving aside how this came to be, I would like to do the following: boost/detail/utf8_codecvt_facet.hpp boost/libs/detail // new directory boost/libs/detai/src/utf8_codecvt_facet.cpp boost/libs/detail/test/test_utf8_codecvt_facet.cpp boost/libs/detail/doc/utf8_codecvt_facet.html This would make both the serialization and program options libraries that much smaller and server our needs until a reviewed version of codecvt facets in added to boost. Robert Ramey

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Program Options Custom Notifier Function Order of Execution
by Tony Han Bao 07 Dec '04

07 Dec '04

Hi all, Can anyone tell me the precise definition or behaviour of the order of execution of the user supplied functions to handle command line options defined in boost program options library. For example, my option menu was defined as follows boost::program_options::options_description menu("Valid Options"); menu.add_options() ("help,h", "Display this menu.") ("time,t", boost::program_options::value<double>(&time_arg_value) -> notifier(&my_function1) "Description of option") ("memory,m", boost::program_options::value<double>(&memory_arg_value) -> notifier(&my_function2), "Description of option") ("file,f", boost::program_options::value<std::vector<std::string> >(&file_arg_value) -> composing() -> notifier(&file_arg_handler<std::vector<std::string> >), "Something"); boost::program_options::variables_map menu_map; boost::program_options::store(boost::program_options:: parse_command_line(argc, argv, menu), menu_map); boost::program_options::notify(menu_map); Question is: Will the following two calls to the program result in different behaviour? >./Test --time 76 --memory 97 --help >./Test --memory 97 --time 76 --help I want my two functions for time and memory be independent of each other but I would like the function be called in the same order as the options specified on the command line. Sure I can test but can someone guarantee that what I discovered will remain valid in the future release of the library. Another question: What will happen if this program was called on the command line with the following options. >./Test --file myfile1 --time 87 --file myfile2 Will the file_arg_handler be called first with composed arguments and then time function (my_function1) or will the time function (my_function1) be called first and then the file_arg_handler function. Can I count on it that what happens will always happen in the future? Is there definitions for the order of execution guarantee by the library? Thanks in advance for your help! Best Regards, Tony Han Bao tonybao(a)mac.com

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Boost Sandbox layout?
by Rene Rivera 06 Dec '04

06 Dec '04

I'm looking at how things are placed in the sandbox and wondering about something... Currently the sandbox mirrors the layout of the main Boost CVS. That is: boost-sandbox /boost/... /libs /libs/<library>/... That layout has a few drawbacks when dealing with a single isolated library... 1) It makes it harder to package as one has to filter out the rest of the stuff there. 2) One can get conflicts when something in another library's code gets accidentally used. I ran into this when evaluating named_params as some MPL related files got picked off from the sandbox instead of from the Boost CVS. 3) Makes finding things much harder when someone mentions to look in the sandbox for their library. Was there ever a discussion as to the layout? (A cursory search did not reveal anything) -- -- Grafik - Don't Assume Anything -- Redshift Software, Inc. - http://redshift-software.com -- rrivera/acm.org - grafik/redshift-software.com - 102708583/icq

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Unexpected behaviour of boost::filesystem::equivalent
by Daniel Krügler 06 Dec '04

06 Dec '04

Hi booster, its quite a long time ago since I could follow the threads here more thoroughly :-( , so the following information might not be new one. During tests of the current Win32 implementation of boost::filesystem::equivalent I observed that the function unexpectingly fails (my test environment was Win XP SP 1 with MSVC7.1) if it compares a "soft link" created via the DOS command "subst" (or its API analogon ::DefineDosDeviceA/W) with the corresponding mapped path object (Lets say I map M: to the existing directory C:\temp). To get an understanding of the test failure I debugged the implementation and found that actually the first test part (getting the handles and comparing the VSN's + further data) gave the expected positive result, but that the very last step, i.e. the comparison of both st_dev values, gave a final unequality. Did others also observe this failure and don't you think that the expected result should show the identity of the underlying path objects? Of course there might be legitimate arguments for the decision for the current behaviour, but I would like to know about them. I am not an expert to argue about the comments in the source code which say that "In theory, volume serial numbers are sufficient to distinguish between devices, but in practice VSN's are sometimes duplicated, so device id is also checked.[..]" The question now is: Should different (MS DOS) device names pointing to the same underlying (Windows NT) device not be compared equivalent? I could think of the following test extension (at least under Windows, regrettably I am not a posix expert to provide a similar solution): If the VSN' and further data have returned a positive result, but the check of both st_dev values fails, one should try to check whether the underlying devices are actually the same, e.g. using the ::QueryDosDeviceA/W API function. What do you think? Greetings, Daniel Krügler

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A few more filesystem documentation corrections
by Edward Diener 06 Dec '04

06 Dec '04

Here are a few more grammatical corrections to the excellent filesystem documentation. Default Name Check mechanism Dangers second sentence: "Since global variables are considered harmful [Wulf-Shaw-73], class path allows the default name check function can be set only once, and only before the first use." should be: "Since global variables are considered harmful [Wulf-Shaw-73], class path allows that the default name check function can be set only once, and only before the first use." or "Since global variables are considered harmful [Wulf-Shaw-73], class path allows the default name check function to be set only once, and only before the first use." Rationale Const vs non-const returns last sentence: "A requirement that path::iterator not be a non-class type was added to eliminate errors non-const iterator errors." should be: "A requirement that path::iterator not be a non-class type was added to eliminate non-const iterator errors." or better: "A requirement that path::iterator be a class type was added to eliminate non-const iterator errors." Finally, in operations.hpp, links on "class directory_iterator" and "other functions" to their explanations further down the page do not work using IE, Netscape, or Opera, so I imagine some HTML error.

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Filesystem documentation error
by Edward Diener 06 Dec '04

06 Dec '04

The documentation to filesystem is outstanding. Congratulation Mr. Dawes ! I did find an error, however. In the class documentation to path.hpp there are two default_name_check member functions. In the specific documentation for default_name_check, there is only a single default_name_check mentioned and the return value in the declaration of the specific documentation has 'void' even while the "Returns:" says otherwise and correctly matches the return value given for either one of the default_name_checks given in the class documentation.

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