March 2008 - Boost - lists.boost.org

[proto] comments on documentation #2
by Markus Werle 16 Mar '08

16 Mar '08

Hi! <anecdote> This morning (6:45 CET) I was sitting at the breakfast table and was reading the printed PDF of proto docs. My little son (6 years old) entered the scene and the first question he asked was: "What kind of puzzle are you trying to solve?". Kids always have a keen sense of what's really going on ... </anecdote> Before I start nagging, I should say that a large subset of the docs are well-done, near perfect. The setup of the first chapters makes it easy to approach proto. But I got lost in the middle with transforms and that is a BadThing (TM), because those are the beasts everybody needs in order to get the maximum out of proto. The transform chapter leaves me with the same feeling I had 1998, 2 weeks after my decision to learn C++, when I was reading Stroustrup's TCPPL chapter about templates. I wish Vandevoorde/Josuttis would have written their book _before_ I had to use templates (and gcc). Same here: I beg for some step-by-step-by-example introduction right now. Nothing of this part of the docs reached my heart and mind. Without tiny little examples I am totally lost here. This serves well as reference documentation, but not as main entry point to a feature of a library. I will try to work through the examples now, but any introductory material appreciated here. Keep me informed about updates in that section, please. Minor issues: First of all: Expression Extensions can go a long way without transforms. So I would recommend to put this chapter in front of the one about transforms. Then introduce transforms later for those with the sword of metaprogramming knowledge and the will to survive. extends<> is useful even without transforms and so why not give it a chance before readers are drawn away by the more advanced, but horrible-to-catch features. Also it might make sense to show an example which uses std::algorithms like the original std::transform example in order to show the power of proto here. AFAICS _make_terminal drops in from heaven without introduction - right? Do we need that one? is terminal<>::type not equivalent? if yes, remove _make_terminal. ------------------------------------- The decltype stuff distracts from the key points. Unaware readers get into panik when seeing static references to types and a keyword yet not in C++. How about typedef ...implementation defined ... result_type; Then move the decltype stuff to the comment paragraph below the code as extra information. Also: why ::result_type and not ::type? Is this consistent with mpl? ----------- Could you provide a full (compilable) example for increment_ints? That would help education (though I feel like I got that one) Maybe even extend the example to an initialization action based on operator new ... ----------- sed -es,no temporaries!,no temporary vectors!,g Maybe state that there are no temporary vectors, but of course the integer 2 in stored as temporary in [2]. Also state that every modern compiler since intel's 8.1 is capable of optimizing that one away, so nobody should care, and then: Look ma! no template code on-board after optimization -> the abstraction penalty is zero! ----------------------------------------------------------- Now it is time to share some time with the kids. Read you later in this group ... Markus

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[1.35][ASIO] Broken index.html
by John Maddock 16 Mar '08

16 Mar '08

The links to the ASIO docs from the main documentation index page is broken, likewise the forwarding HTML file in libs/asio also forwards to a non-existent file. So.... where have the docs moved to... or were they not committed? Thanks, John.

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[proto] comments on documentation #1
by Markus Werle 15 Mar '08

15 Mar '08

Hi! This is a proposal for extra text which might have helped me to catch some things right from the beginning: Section "Accessing Children Nodes": Subsection "Expression Nodes as fusion sequnces" After "... arguments in order" please insert an improved version of the following paragraph (intended for first-contact-to-proto people like me) --- Note that in C++ operators are nothing else but special syntax for operations that can be written as function calls, e.g. a+b is equivalent to binary_plus(a, b). Proto "thinks" of operators in this way and - as introduced above - uses a type representation of the form expr<tag::binary_plus, typeA, typeB> This is why function calls are nothing special to proto and and are handled in analogy to operators: For function calls the type representation has a tag tag::function and the type of function is stored as extra template argument, so you obtain type representations of the form expr<tag::function, typeFunction, typeA, typeB> for a function call Function(A, B). So if a compile time algorithm in proto needs only access to the types of the arguments and not to the type of the function, the first argument has to be removed from the sequence. We will come back to this in a second: [Then show the example and then in the explanation add:] What happens during compilation with "fun(1, 2, 3, 4)"? The type of fun is in namespace proto, so it is "tainted" with Proto-ness exactly like _1 in the examples above. Similar to _1 + 2, which has a return type of expr<tag::binary_plus, ....> ;-) \footnote{Once in a time binary operator+ was tagged tag::plus, which led to trouble for the tag name of unary operator+. A lot of crazy proposals for the tag name were made, now we simply use tag::binary_plus and tag::unary_plus, no further discussions needed} ;-) the call fun(...) has a return type of expr<tag::function, PUT_SOME_CODE_HERE, ....> The integers are automatically wrapped in terminal<int>s. That's why proto is so cool. Since we are only interested in the arguments of the function call and already know that expression nodes are valid Fusion sequences and know that the first element in the fusion sequence is the function type, namely terminal<fun_t>::type alias expr<tag::terminal, bla bla>, we use a compile time algorithm which drops the first element from the list before pushing the result through other very useful algorithms of boost::fusion - in this example for_each and transform (Did we already mention that you are lost with proto if you do not know fusion?) ----------------------------- Markus

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[proto] docs: Calc2 improvement proposal
by Markus Werle 15 Mar '08

15 Mar '08

Hi! First of all: This is a very nice example. Fantastic idea to introduce index information stored in the terminals at this place in the docs - perfect. If you define arg as template<int I> struct arg {}; and change the code accordingly the reader is not in need to know anything about mpl::int_ and IMHO the code template <int I> double operator ()(proto::tag::terminal, arg<I>) const { return d[ I - 1 ]; } is easier to read than template<typename I> double operator ()(proto::tag::terminal, arg<I>) const { return d[ I() - 1 ]; } Note that this should be written for beginners like me, so one catches the idea immediately without taking the extra path to mpl here. Markus

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[filesystem] wpath_traits missing BOOST_FILESYSTEM_DECL
by Alexei Alexandrov 15 Mar '08

15 Mar '08

Hi, In Boost 1.34.1 the wpath_traits class misses BOOST_FILESYSTEM_DECL declaration and thus cannot be used with boost::filesystem is dynamically linked on Windows. Is this a bug or it's me who misses something? -- Alexei Alexandrov

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filesystem::wpath and Linux
by Johan Ström 15 Mar '08

15 Mar '08

Hello list! Im working on an app wich is to run on windows, linux and OSX. I just switched from using filesystem::path to wpath, to be able to use i18n'ed paths on Windows. However this gave me a bunch of problems on Linux. A simple test case: test.cpp #include <iostream> #include <boost/filesystem/path.hpp> #include <boost/filesystem/convenience.hpp> namespace fs = boost::filesystem; int main() { fs::wpath mypath(L"/tmp/some/Directories"); for(int i = 0; i < 10; i++) { try { std::wcout << "Creating " << mypath << " nr " << i; fs::create_directories(mypath); }catch(std::exception&e) { std::cout << e.what() <<std::endl; } } } And Jamfile: import modules ; BOOST_ROOT = [ modules.peek : BOOST_ROOT ] ; use-project /boost : $(BOOST_ROOT) ; project wpathtest : requirements <library>/boost/filesystem//boost_filesystem/<link>static ; exe test : test.cpp : ; Running this in GDB on Linux with gcc 4.1.1, boost 1.34.1 (.0 too): (gdb) % dev1 ~/testcase$ gdb ./bin/gcc-4.1.1/debug/test GNU gdb Red Hat Linux (6.3.0.0-1.143.el4rh) Copyright 2004 Free Software Foundation, Inc. GDB is free software, covered by the GNU General Public License, and you are welcome to change it and/or distribute copies of it under certain conditions. Type "show copying" to see the conditions. There is absolutely no warranty for GDB. Type "show warranty" for details. This GDB was configured as "i386-redhat-linux-gnu"...Using host libthread_db library "/lib/tls/libthread_db.so.1". (gdb) run Starting program: /home/johan/testcase/bin/gcc-4.1.1/debug/test Creating /tmp/some/Directories nr 0 *** glibc detected *** double free or corruption (out): 0x0891e858 *** Program received signal SIGABRT, Aborted. 0x001cf7a2 in _dl_sysinfo_int80 () from /lib/ld-linux.so.2 (gdb) where #0 0x001cf7a2 in _dl_sysinfo_int80 () from /lib/ld-linux.so.2 #1 0x002107a5 in raise () from /lib/tls/libc.so.6 #2 0x00212209 in abort () from /lib/tls/libc.so.6 #3 0x00244a1a in __libc_message () from /lib/tls/libc.so.6 #4 0x0024b2bf in _int_free () from /lib/tls/libc.so.6 #5 0x0024b63a in free () from /lib/tls/libc.so.6 #6 0x00654041 in operator delete () from /usr/lib/libstdc++.so.6 #7 0x0065408d in operator delete[] () from /usr/lib/libstdc++.so.6 #8 0x0804e233 in boost::checked_array_delete<char> (x=0x891e858 "\200 \200\200\200\200��\200\200\200\200�\200\200\200\200�\200\200 \200\200p") at /home/common/boost_1_34_1/boost/checked_delete.hpp:41 #9 0x0804e249 in ~scoped_array (this=0xbfefada0) at /home/common/ boost_1_34_1/boost/scoped_array.hpp:65 #10 0x0804f983 in boost::filesystem::wpath_traits::to_external (ph=@0xbfefaf1c, src=@0xbfefadfc) at /home/common/boost_1_34_1/libs/ filesystem/src/path.cpp:96 #11 0x0804af53 in boost::filesystem::basic_path<std::basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >, boost::filesystem::wpath_traits>::external_file_string (this=0xbfefaf1c) at /home/common/boost_1_34_0/boost/filesystem/ path.hpp:302 #12 0x0804b917 in boost::filesystem::exists<boost::filesystem::basic_path<std::basic_strin g<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >, boost::filesystem::wpath_traits> > (ph=@0xbfefaf1c) at /home/common/ boost_1_34_0/boost/filesystem/operations.hpp:279 #13 0x0804ba6d in boost::filesystem::exists (ph=@0xbfefaf1c) at /home/ common/boost_1_34_0/boost/filesystem/operations.hpp:601 #14 0x0804c06d in boost::filesystem::create_directories<boost::filesystem::basic_path<std: :basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >, boost::filesystem::wpath_traits> > (ph=@0xbfefaf1c) at /home/common/boost_1_34_0/boost/filesystem/ convenience.hpp:42 #15 0x0804c219 in boost::filesystem::create_directories (ph=@0xbfefaf1c) at /home/common/boost_1_34_0/boost/filesystem/ convenience.hpp:88 #16 0x0804c1b3 in boost::filesystem::create_directories<boost::filesystem::basic_path<std: :basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >, boost::filesystem::wpath_traits> > (ph=@0xbfefaf7c) at /home/common/boost_1_34_0/boost/filesystem/ convenience.hpp:51 #17 0x0804c219 in boost::filesystem::create_directories (ph=@0xbfefaf7c) at /home/common/boost_1_34_0/boost/filesystem/ convenience.hpp:88 #18 0x0804c1b3 in boost::filesystem::create_directories<boost::filesystem::basic_path<std: :basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >, boost::filesystem::wpath_traits> > (ph=@0xbfefafc0) at /home/common/boost_1_34_0/boost/filesystem/ convenience.hpp:51 #19 0x0804c219 in boost::filesystem::create_directories (ph=@0xbfefafc0) at /home/common/boost_1_34_0/boost/filesystem/ convenience.hpp:88 #20 0x0804a4c0 in main () at test.cpp:14 (gdb) If I instead remove the for/try stuff (only keep fs::wpath and fs::create_directories(mypath) and the std::wcout, I get this: (gdb) run Starting program: /home/johan/testcase/bin/gcc-4.1.1/debug/test Creating /tmp/some/Directories nr terminate called after throwing an instance of 'boost::filesystem::basic_filesystem_error<boost::filesystem::basic_path <std::basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >, boost::filesystem::wpath_traits> >' what(): boost::filesystem::wpath::to_external conversion error Program received signal SIGABRT, Aborted. 0x001cf7a2 in _dl_sysinfo_int80 () from /lib/ld-linux.so.2 (gdb) where #0 0x001cf7a2 in _dl_sysinfo_int80 () from /lib/ld-linux.so.2 #1 0x002107a5 in raise () from /lib/tls/libc.so.6 #2 0x00212209 in abort () from /lib/tls/libc.so.6 #3 0x006571bb in __gnu_cxx::__verbose_terminate_handler () from /usr/ lib/libstdc++.so.6 #4 0x00654ed1 in __cxa_call_unexpected () from /usr/lib/libstdc++.so.6 #5 0x00654f06 in std::terminate () from /usr/lib/libstdc++.so.6 #6 0x0065504f in __cxa_throw () from /usr/lib/libstdc++.so.6 #7 0x0804b69c in boost::throw_exception<boost::filesystem::basic_filesystem_error<boost:: filesystem::basic_path<std::basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >, boost::filesystem::wpath_traits> > > (e=@0xbfeed054) at /home/common/ boost_1_34_0/boost/throw_exception.hpp:39 #8 0x0804f669 in boost::filesystem::wpath_traits::to_external (ph=@0xbfeed1cc, src=@0xbfeed0ac) at /home/common/boost_1_34_0/libs/ filesystem/src/path.cpp:94 #9 0x0804ad15 in boost::filesystem::basic_path<std::basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >, boost::filesystem::wpath_traits>::external_file_string (this=0xbfeed1cc) at /home/common/boost_1_34_0/boost/filesystem/ path.hpp:302 #10 0x0804b6d9 in boost::filesystem::exists<boost::filesystem::basic_path<std::basic_strin g<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >, boost::filesystem::wpath_traits> > (ph=@0xbfeed1cc) at /home/common/ boost_1_34_0/boost/filesystem/operations.hpp:279 #11 0x0804b82f in boost::filesystem::exists (ph=@0xbfeed1cc) at /home/ common/boost_1_34_0/boost/filesystem/operations.hpp:601 #12 0x0804be2f in boost::filesystem::create_directories<boost::filesystem::basic_path<std: :basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >, boost::filesystem::wpath_traits> > (ph=@0xbfeed1cc) at /home/common/boost_1_34_0/boost/filesystem/ convenience.hpp:42 #13 0x0804bfdb in boost::filesystem::create_directories (ph=@0xbfeed1cc) at /home/common/boost_1_34_0/boost/filesystem/ convenience.hpp:88 #14 0x0804bf75 in boost::filesystem::create_directories<boost::filesystem::basic_path<std: :basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >, boost::filesystem::wpath_traits> > (ph=@0xbfeed22c) at /home/common/boost_1_34_0/boost/filesystem/ convenience.hpp:51 #15 0x0804bfdb in boost::filesystem::create_directories (ph=@0xbfeed22c) at /home/common/boost_1_34_0/boost/filesystem/ convenience.hpp:88 #16 0x0804bf75 in boost::filesystem::create_directories<boost::filesystem::basic_path<std: :basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >, boost::filesystem::wpath_traits> > (ph=@0xbfeed278) at /home/common/boost_1_34_0/boost/filesystem/ convenience.hpp:51 #17 0x0804bfdb in boost::filesystem::create_directories (ph=@0xbfeed278) at /home/common/boost_1_34_0/boost/filesystem/ convenience.hpp:88 #18 0x0804a2f3 in main () at test.cpp:10 The double-delete doesnt look too good, does it? The other problem, this makes wpath pretty useless in crossplatform if it cannot decode itself? Even when its such a simple path.. I've done some googling on wpath but there doesnt seem to be very much usage of it.. Any clues? Thanks! -- Johan Ström Stromnet johan(a)stromnet.se http://www.stromnet.se/

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[filesystem] imbue for path_traits
by Alexei Alexandrov 15 Mar '08

15 Mar '08

Hi, Currently filesystem::path_traits doesn't have imbue() method while wpath_traits has. Thus, there is explicit assumption that external and internal encodings for path are the same. But this is not true sometimes. For example, currently it doesn't seem to be possible to use filesystem::path conveniently on Linux in cases when internal encoding of the application is UTF-8 while system encoding might differ from UTF-8 (GB2312, for example).

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[1.35][Property Tree] In or out for 1.35?
by John Maddock 15 Mar '08

15 Mar '08

Do we have a final decision on whether Property Tree is in Boost-1.35 or not? At present it's there in the SVN release branch, but without docs and no link from the main documentation index either :-( I guess my vote at this very late stage is to remove it from the release branch for 1.35, but leave it in Trunk? John.

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gcc-4.3 support
by Tim Blechmann 15 Mar '08

15 Mar '08

hi all, since gcc-4.3 has been released a short time ago, i'm curious about the plans for supporting it in boost 1.35 ... the ticket tracker does contain a few patches for gcc-4.3, which haven't been included in the trunk, yet ... http://svn.boost.org/trac/boost/query? status=new&status=assigned&status=reopened&summary=~4.3&order=priority any plans to include them before 1.35 is out? thnx, tim -- tim(a)klingt.org http://tim.klingt.org Cheat your landlord if you can and must, but do not try to shortchange the Muse. It cannot be done. You can't fake quality any more than you can fake a good meal. William S. Burroughs

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[Proto] review period extended to end March 28th
by Hartmut Kaiser 15 Mar '08

15 Mar '08

Hi all, There have been several requests to extend the Proto review period. For this reason the review now will end on March 28th. This should give you sufficient time to have a closer look at the library and to prepare a review. The original announcement follows: The review of Eric Nieblers Proto library starts today, March 1st 2008, and will end on March 14th. I really hope to see your vote and your participation in the discussions on the Boost mailing lists! --------------------------------------------------- About the library: Proto is a framework for building Domain Specific Embedded Languages in C++. It provides tools for constructing, type-checking, transforming and executing expression templates. More specifically, Proto provides: * An expression tree data structure. * Operator overloads for building the tree from an expression. * Utilities for defining the grammar to which an expression must conform. * An extensible mechanism for immediately executing an expression template. * An extensible set of tree transformations to apply to expression trees. * A mechanism for giving expressions additional behaviors and members. Documentation is here: http://boost-sandbox.sourceforge.net/libs/proto Download proto.zip from here: http://www.boost-consulting.com/vault/index.php?directory=Template%20Metapro gramming Proto is a very important infrastructure library, IHMO. It has been used as the backbone for several other library writing efforts already, such as Xpressive and the rewrite of Spirit (there it has been used for all three parts: the parser, the lexer and the generator modules), and it is a key enabling technology in the long-planned unification of Phoenix and the Lambda Library. --------------------------------------------------- Please always state in your review, whether you think the library should be accepted as a Boost library! Additionally please consider giving feedback on the following general topics: - What is your evaluation of the design? - What is your evaluation of the implementation? - What is your evaluation of the documentation? - What is your evaluation of the potential usefulness of the library? - Did you try to use the library? With what compiler? Did you have any problems? - How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? - Are you knowledgeable about the problem domain? Regards Hartmut Review Manager

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