March 2008 - Boost - lists.preview.boost.org

[proto] docs unclear (to me) for: "Expression Nodes as Fusion Sequences"
by Markus Werle 12 Mar '08

12 Mar '08

Hi! In the section "Expression Nodes as Fusion Sequences" you show the follwing code struct fun_t {}; terminal<fun_t>::type const fun = {{}}; // ... fusion::for_each( fusion::transform( // pop_front() removes the "fun" child fusion::pop_front(fun(1,2,3,4)) // Extract the ints from the terminal nodes , functional::arg<>() ) , display() ); It did not became clear to me why a terminal<fun_t>::type can be initialized with 4 integer arguments. I thought terminal<fun_t>::type is equivalent to expr< tag::terminal, args0< fun_t >, 0 > and should take no args at all. Could you clarify this? Markus

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shifted_ptr w/ make_shifted_ptr
by Phil Bouchard 12 Mar '08

12 Mar '08

Ok, I replaced former macro with make_shifted_ptr<>() constructor and allocator function. Like previously mentionned the template parameters of that function add the "const" modifier; therefore it cannot emulate constructors having non-const references. I was reading about the new variadic template arguments that was added in the new compiler... I haven't tried it yet but I am afraid the same problem will happen. Furthermore, I decided not to replace type of "owned<>::p_" with "optional<>" because it doesn't reflect the same purpose and adds an unwanted boolean flag. Regards, -Phil

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Problem linking Boost Unit Test Library on windows (1.33.0)
by Duft Markus 11 Mar '08

11 Mar '08

Hi! I have a problem linking our application on windows. Somebody added test cases using the boost unit test library, and since then windows won't link anymore. The problem is, that the boost library contains a "main" and doesn't seem to contain a "init_unit_test_suite" function (am I missing a library?). It works on all other systems, is windows unsupported there? Is there any more information I should gather for you to see the problem, or is this a known issue (I remember seeing something on the list about this, but I think it was about a newer boost version. Can any eventually made changes be expressed as a patch for 1.33.0 so I can locally fix the issue, and won't need an upgrade)? Cheers, Markus

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shared_ptr in multithreaded environments
by Mathias Gaunard 11 Mar '08

11 Mar '08

I see that shared_ptr is quite costly in multithreaded environments cause it would need DCAS, and thus uses a spinlock in cases where it is not available. intrusive_ptr, which is only one word, does not need that. Shouldn't intrusive_ptr be put forward more, then? Or better, why not make a shared_ptr-like shared_obj, a container, responsible for allocating the object, thus able to allocate a struct { T value; int refcount; } instead of T's, and advocate its usage? Such an interface could also trivially use a good garbage collection algorithm instead of refcounting. It seems to me that shared_ptr was made inefficient by design, which is not a really good thing since it is getting more and more popular. Could someone confirm or infirm this?

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[proto] Manual as PDF?
by Markus Werle 11 Mar '08

11 Mar '08

Hi! Currently I am under high pressure at work, but would like to get into the proto details even in the absence of a web browser. I found it helpful to have things printed (unsafe trees here) in such a situation. So could someone with a working toolchain be so kind and generate a PDF out of the documentation sources and put it into the vault? Thanks, Markus

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Trac open bugs - by assignee
by Marshall Clow 11 Mar '08

11 Mar '08

[ 221 open bugs today, 220 yesterday ] If you are maintaining a library, and have not logged into the trac system at <http://svn.boost.org/trac/boost/>, please do so ASAP. Until you do that, no tickets can be assigned to you, and will remain under "None". Instructions on working with tickets can be found at: <http://svn.boost.org/trac/boost/wiki/TicketWorkflow> and a mapping of user names to "real names" can be found at: <http://svn.boost.org/trac/boost/report/16> Bug summary 23 djowel 20 az_sw_dude 14 grafik 13 dgregor 12 vladimir_prus 12 doug_gregor 12 dave 11 agurtovoy 10 no-maintainer 9 bemandawes 8 anthonyw 7 turkanis 7 jsiek 6 johnmaddock 5 witt 5 igaztanaga 4 ebf 3 t_schwinger 3 ramey 3 matias 3 danielw 3 None 2 shammah 2 rogeeff 2 pavol_droba 2 nesotto 2 nasonov 2 kaalus 2 jmaurer 2 hkaiser 2 danieljames 2 aaron_windsor 1 urzuga 1 speedsnail 1 samuel_krempp 1 pdimov 1 marshall 1 hljin 1 garcia 1 dlwalker None 1493 SVN files making it through to install None 1644 Boost.Test missing documentation file BOOST_CHECK_CLOSE_FRACTION.html None 1666 Visualizer for boost::optional aaron_windsor 1622 Adjacency list needs to handle self-edges correctly aaron_windsor 778 top-level configure is broken agurtovoy 1001 gcc 4.1.2 segfaults on mpl/test/apply.cpp agurtovoy 1051 MPL header ordering triggers bug agurtovoy 1099 unable to iterate through a "non-explicitly-declared" mpl::set agurtovoy 1215 Boost 1.34.1_ mpl: Wrong workaround detection using MinGW32 (or.hpp_ line #33) agurtovoy 1317 has_xxx randomly broken in msvc agurtovoy 1469 [mpl] nested typedef of set has two different meanings agurtovoy 1476 always<> is not nullary. agurtovoy 1528 g++ 4.3.0 reports error because of redeclaration of next agurtovoy 1549 Boost.MPL: 'index_of' algorithm is not documented agurtovoy 1568 duplicate include guards agurtovoy 588 mpl::remove compile error with gcc 4.1.0 anthonyw 1154 tss destruction segfaults in conjunction with dlopen/dlclose anthonyw 1168 [thread] tss crashes randomly anthonyw 1268 xtime_cmp changes to deal with overflow were reverted anthonyw 1470 Boost.Thread: Compilation errors with non-__cdecl calling convention anthonyw 1640 [Thread] warnings from VC9 + warning level 4 anthonyw 1657 Bug in boost::threads sample anthonyw 876 xtime documentation incomplete anthonyw 881 errors when build with Apache stdcxx az_sw_dude 1028 typo in boost header: date_time/time_defs.hpp az_sw_dude 1078 from_iso_string cannot read the output from to_iso_string az_sw_dude 1098 Urgent libboost-date-time1.33.1 : bugs on ia64 ? az_sw_dude 1147 date_time library contains global #define ERROR az_sw_dude 1160 warning: month_format shadows a member of this az_sw_dude 1162 warning: ticks shadows a member of this az_sw_dude 1289 posix_time::time_facet forgets to pass a_ref argument to base class az_sw_dude 1299 change in typedef stringstream_type in format_date_parser.hpp causing compilation error az_sw_dude 1306 invalid docbook in date_period.xml az_sw_dude 1384 Linking problem with date_time library on Visual C++ 2008 Express az_sw_dude 1386 date_time documentation Jamfile breaks building of boost docs az_sw_dude 1524 format_date_parser.hpp(221) : cannot convert parameter 1 az_sw_dude 1574 operator<< for boost::posix_time::ptime ignores ostream flags az_sw_dude 1674 date_time::date_formatting.hpp: incorrectly formats year using global locale az_sw_dude 287 wrong usage of ios_base::narrow az_sw_dude 316 date_time type conversion warning az_sw_dude 604 from_ftime incorrectly processes FILETIME filled with zeros az_sw_dude 642 operator<< for gregorian::date_duration not found az_sw_dude 889 Insane Dependencies az_sw_dude 890 date_time library supports only the current dst rule bemandawes 1378 filesystem path invalid name for hidden files (LINUX) bemandawes 1389 filesystem::ostream << boost::format generates operator ambigious error (in MSVC++) bemandawes 1458 Darwin Tiger throws std::runtime_error: locale::facet::_S_create_c_locale name not valid bemandawes 1578 bug in readdir_r_simulator() in a multi-threaded environment bemandawes 1583 Serious flaw in boost::filesystem filename handling (opensuse) bemandawes 1589 [filesystem] 'mbstate_t' : is not a member of 'std' bemandawes 1606 filesystem/src/exception.cpp doesn't build with gcc bemandawes 1613 Link Errors against file_system on OS X with Intel Version 10.1 C++ compilers bemandawes 752 directory_iterator doesn't work with catch danieljames 1554 When BOOST_HASH_NO_EXTENSIONS is defined hash doesn't support new string types. danieljames 1555 When BOOST_HASH_NO_EXTENSIONS is defined hash doesn't support boost::system::error_code danielw 1044 Argument pack inaccessable in a functions return type danielw 1054 Parameter takes an "infinite" amount of time to compile with the Intel compiler. danielw 1097 keyword.hpp generates many warnings C4180: qualifier applied to function type has no meaning; ignored dave 1010 linking boost.python on freebsd dave 1019 iterator_facade::pointer should be the return type of operator-> (DR 445) dave 1085 Python rules for compiling in Mac OS X dave 1179 [boost.python] can not export a union in VC2005sp1 dave 1181 [boost.python] can modify enum value dave 1387 Review / update docs to reflect changes dave 1460 Python classes with multiple bases are convertible only to the first class in the lists dave 1482 boost::python::throw_error_already_set should be marked noreturn dave 1516 [python] Failing VC9 regression tests dave 1599 [python] '_set_se_translator': identifier not found dave 865 Use of C++0x keyword as identifier dave 910 gcc strict-aliasing problems with python dgregor 1164 Floyd Warshall broken with unsigned edge weights dgregor 1192 [boostbook] problem when two files have the same name dgregor 1199 configure doesn't work with path containing whitespaces (MacOS X) dgregor 1310 [result_of] const-qualified function pointer doesn't work dgregor 1326 Unable to check graph isomorphism using LEDA adapter dgregor 1391 dominator_tree_test on Borland/CodeGear outputs overly long line dgregor 1394 Translate libs/graph/build/python/Jamfile to BBv2 dgregor 1395 Write Tests for Python Bindings dgregor 1630 gcc-4.3: adjacency_list.hpp includes deprecated header dgregor 1655 Documentation of the depth_first_search() Function dgregor 556 Bundled graph properties dgregor 732 Johnson All-Pairs needs better "no path" information dgregor 736 Const correctness violation djowel 1170 Emit Warnings instead of # symbols in the syntax highlighter djowel 1171 Quickbook title output djowel 1172 non-utf djowel 1176 Space after inline code djowel 1206 Escaping from within code? djowel 1273 CR+LF newlines in position_iterator djowel 1276 spirit problem with _GLIBCXX_DEBUG djowel 1277 Closing section like [pre with } causes Quickbok to crash djowel 1280 sections in imported source files get put inside <para> elements in docbook output djowel 1281 Quickbook produces invalid BoostBook/DocBook XML djowel 1324 tuple should have a swap() that operates element-by-element djowel 1396 wrong result_of invocation around transform_view djowel 1436 [quickbook] inline code inside headings djowel 1484 Quickbook produces illegal docbook for some docinfo fields. djowel 1500 [Spirit/Phoenix] C4512 Compiler warnings from VC8 djowel 1570 Some boost headers aren't ready for gcc 4.3 djowel 1600 duplicate include guard djowel 1601 distane of boost::tuple djowel 1607 Tuple Library Documentation Changes djowel 1610 [MSVC/STLport] [tree/common.hpp] Standard library requirements violation(incomplete type as vector parameter) djowel 1614 vector workaround needed for MSVC9 djowel 1617 spirit gcc-4.3 fix djowel 1619 [Fusion] C4512 warnings from VC9 (Visual Studio 2008) dlwalker 613 boost/crc.hpp uses non-standard conforming syntax doug_gregor 1021 [Graph][reverse_graph] Problem using reverse_graph adapter with an adapted user defined graph doug_gregor 1076 compile error: disconnecting struct with operator()() doesn't work in VS2005 SP1 doug_gregor 375 LEDA graph adaptors do not handle hidden nodes properly doug_gregor 402 random_vertex/random_edge are unnecessarily inefficient doug_gregor 403 Document copy_component doug_gregor 447 reverse_graph and constness of property maps doug_gregor 708 Dijkstra no_init version should not require VertexListGraph doug_gregor 733 Numbered headers don't work with "preferred" syntax doug_gregor 735 Fruchterman-Reingold grid performance can be improved doug_gregor 738 Memory leaks with signal::connect? doug_gregor 829 Implicit graph not implement doug_gregor 852 Problem with Boost and GCC 4.1 ebf 1507 [variant] C4512 warnings from VC8.0 ebf 1548 [variant][docs]typo: formal arg_ operand_ should be v in times_two arglist ebf 1654 recursive variants do not handle nested variants correctly. ebf 993 Variant should use least common multiple of alignments_ rather than maximum garcia 1581 Boost.MultiArray: Resizing bug if the index is not 0-based grafik 1041 Cygwin requires PATH setting. grafik 1322 trac rejects patch attachment as spam grafik 1417 Regresson tests hang in Darwin (Tiger) grafik 1430 Regression fails under Cygwin grafik 1433 Trac's spam detection rejects too many valid messages grafik 1512 Broken link to vacpp in bjam docs. grafik 1513 Broken link to bcpp in bjam docs. grafik 1571 boost bugtracker displays a patch incorrectly grafik 1576 cannot read non-ASCII output messages grafik 1577 Some commands don't work because hStdInput == 0 grafik 1663 build.bat cannot set/reset ERRORLEVEL grafik 616 Boost Jam_ and non english directorys grafik 959 linking fails when Boost is compiled with STLport 5.1.* on Linux (names mismatch) grafik 986 Problem building Python modules on boost 1.34.0 hkaiser 1079 boost-1.34.0 fails to compile. concept checks not satisfied. hkaiser 1670 wave almost unusably slow on real-world input hljin 1522 bit_range friend decl in bit_aligned_pixel_reference.hpp needs to be fully qualified for gcc 4.3 mainline igaztanaga 1080 boost::interprocess win32 global file mapping issue igaztanaga 1210 interprocess::barrier hangs during second use under linux (boost 1.33.1) igaztanaga 1390 Interpocess: managed shared memory failing completely under OS X igaztanaga 1634 boost::interprocess::vector cannot contain volatile int igaztanaga 1635 Incomplete include guard in boost/intrusive jmaurer 351 Diff in state of mersenne_twister gen between GCC3.41 & CW9 jmaurer 599 uniform_01 copies engine instead of using a reference johnmaddock 1081 Empty string rejected as perl-style regex johnmaddock 1314 Using SSE-intrinsics in VC8 causes static assert in type_with_alignment.hpp johnmaddock 1411 Fix BOOST_PARTIAL_SPECIALIZATION_EXPLICT_ARGS johnmaddock 1446 POSIX API doesn't use C locale johnmaddock 1451 error: use of C99 long long integer constant johnmaddock 1626 [type_traits] "bad_alloc is not a member of std" in has_virtual_destructor_test.cpp jsiek 1531 segfault in dynamic_bitset::reference assign operator jsiek 1540 Poisson distribution very slow for large mean (and may also overflow). jsiek 575 Calling subgraph::global_to_local on a root graph jsiek 636 strange compiling problem for transitive_closure jsiek 815 remove_edge core dumps on self-circle jsiek 875 No iterator based constructor for adjacency_matrix jsiek 900 graphml reader namespace handling is broken kaalus 1184 property_tree assignment (operator) bug kaalus 1604 property_tree xml parser doesn't compile with gcc marshall 1252 [pool] severe overhead with unaligned sizes. matias 1406 Understanding the Tables outdated matias 1651 incorrect typedefs in examples matias 1676 Dead links on Boost.Test example documentation. nasonov 1220 lexical_cast requires RTTI nasonov 754 boost::any - typeid comparison across shared boundaries nesotto 1629 range/iterator_range.hpp bug nesotto 1675 [range] VC8 - compiler warnings when including range/array headers no-maintainer 1068 Mersenne twister disables streaming for Visual C++ no-maintainer 1222 lambda::ret<T> should declare result_type. no-maintainer 1270 uniform_smallint doesn't compile with lagged_fibonacci random number generators no-maintainer 1515 [lambda] C4512 warnings from VC8.0 no-maintainer 1544 uniform_01 w/ref template param causes ref to ref error no-maintainer 1546 Method boost::random::uniform_int::operator()(engine_ value) is missing no-maintainer 1572 [lambda] smart pointer const-ness affects its contents no-maintainer 1632 Default Interval rounding policies incomplete no-maintainer 781 Lambda: (_1 + "y")(string("x")) Doesn't Compile no-maintainer 819 uniform_int<> with type's maximum availaible range error pavol_droba 1152 rle_example fails pavol_droba 1385 begin must be boost-qualified pdimov 1106 shared_ptr<T> should not convert to shared_ptr<U> when T* doesn't convert to U* ramey 1285 [serialization] problem when including shared_ptr_132.hpp ramey 1628 Lack of wide character support prevents boost.serialization from linking ramey 1662 boost::serialization for boost::optional - missing include rogeeff 1383 signal.h features not found on Mac OS rogeeff 1542 [test] compiler errors when building with stdcxx library samuel_krempp 859 boost::format ignores a user defined locale shammah 290 perfomance: memory cleanup for pool takes too long shammah 386 boost::pool_allocator breaks with vector of vectors speedsnail 1138 Problems with TSS and static thread library t_schwinger 1100 Building boost.function_types fails cvs rev-1.1_ no chdir command in bash t_schwinger 1602 function_types Jamfile depends on the source tree being in a specific place. t_schwinger 1653 wave executable erroneously required for build of function_types lib turkanis 1523 [iostreams] VC8/VC9 compiler warnings turkanis 1545 [boost/rational.hpp] 'noskipws' is not a member of 'std' turkanis 1579 gzip compressor should model DualUseFilter turkanis 1580 Add static assert to prohibit instantiating a chain with mode dual_use turkanis 1649 Fix definition of JavaScript menu to avoid long chains of functions turkanis 1656 Consider implementing flush() for symmetric filters turkanis 1671 type mismatch of buffer size parameter causes overload resolution to fail urzuga 574 [boost::lambda] Compile error with libstdc++ debug mode vladimir_prus 1165 more quoting problems vladimir_prus 1274 Useless error message vladimir_prus 1321 invalid docbook in tool documentation vladimir_prus 1527 [program_options] Second (and subsequent) lines in tabbed text not aligned correctly vladimir_prus 1530 Program options documentation - Overview - Syntactic Information example typo vladimir_prus 1537 no value given in 'mysql_password =' vladimir_prus 1584 cryptic bbv2 error building quickbook vladimir_prus 1587 [program_options] crashes if value part missing in external configuration file vladimir_prus 1588 [program_options] crashes if value part missing in external configuration file vladimir_prus 1645 Invalid unicode support for default_value vladimir_prus 469 multitoken broken vladimir_prus 689 [program_options] Endless loop with long default arguments witt 1046 Boost.Python quickstart instructions mention nonexistent target witt 583 Fixes for build on IBM pSeries for AIX and Linux witt 834 Homepage regression links witt 957 The "Getting Started" page does not mention the stdlib option witt 973 zip_iterator has value_type == reference -- -- Marshall Marshall Clow Qualcomm, Inc. <mailto:mclow@qualcomm.com> The famous British scientist, Lord Kelvin, said: "When you measure what you are speaking about and express it in numbers, you know something about it, but when you cannot (or do not) measure it, when you cannot (or do not) express it in numbers, then your knowledge is of a meagre and unsatisfactory kind."

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[Iostreams] Confusion with devices
by Robert Dailey 11 Mar '08

11 Mar '08

Hi, >From my research on Iostream devices, I cannot understand why my read() statement's 'count' parameter is receiving a value of 4096. For example, I've implemented a seekable_device_tag category device that provides direct binary disk access. My stream is defined as follows: typedef boost::iostreams::stream<DiskDevice> DiskStream; DiskStream stream; char* buffer; // assume this is a valid buffer stream.read( buffer, 8 ); The code above (at least to me) should be reading in 8 char's (bytes) of data from the stream. However, if I set a break point in DiskDevice::read(), the second parameter (named count) receives a value of 4096, which eventually gets passed into fread() and causes an exception. I also noticed that boost::iostreams::stream derives from the standard streams, which I imagine is causing the problems. For direct binary disk access, should I avoid boost.iostreams all together? I don't like that boost::stream is going through std::iostream::read() before reaching my device's read function. Perhaps, also, I am misunderstanding Boost.Iostreams. Please clarify. Thanks.

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Re: [boost] UTF-8 conversion etc. (Cory Nelson)
by Graham 11 Mar '08

11 Mar '08

>> Sebastian, >> >> >> >> As Unicode characters that are not in page zero can require more than 32 >> bits >> >> to encode them [yes really] this means that one 'character' can be very >> long > >Unicode defines codepoints from 0 to 10FFFF - this can be encoded with >32 bits in UTF-8 and UTF-16. Cory, This is true for simple characters, except that current Unicode specs require support for surrogates - which require twice that -and thats even before you start to discuss logical grouping of characters or graphemes which can themselves be two or three characters long. I am glad you recognise that normalisation support is difficult - that's why we the character support library is the hard part to develop. I guess we just ran out of steam after that. Yours, Graham

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SOC application draft
by John Maddock 11 Mar '08

11 Mar '08

The deadline for mentoring organisations is this Wednesday, so we really need to get organised - in particular we need a preliminary list of mentors by that time! In the mean time at Jeff's suggestion I've attached below a draft of our application so you all get to critique it :-) Regards, John. Here comes the draft.... 1) What is your Organization's Name? Boost C++ Libraries 2) What is your Organization's Homepage? www.boost.org 3) Describe your organization. Boost provides free peer-reviewed portable C++ source libraries. We emphasize libraries that work well with the C++ Standard Library. Boost libraries are intended to be widely useful and usable across a broad spectrum of applications. The Boost license encourages both commercial and non-commercial use. We aim to establish "existing practice" and provide reference implementations so that Boost libraries are suitable for eventual standardization. Ten Boost libraries are already included in the C++ Standards Committee's Library Technical Report (TR1) as a step toward becoming part of a future C++ Standard. More Boost libraries are proposed for the upcoming TR2. 4) Why is your organization applying to participate in GSoC 2008? What do you hope to gain by participating? Our aim in applying is twofold: to nurture long term Boost and/or other open source participation, and to obtain useful contributions to the Boost C++ libraries. In past years we believe we have achieved both of these aims, and would like to do the same this year. 5) Did your organization participate in previous GSoC years? If so, please summarize your involvement and the successes and failures of your student projects. (optional) We participated in 2006 and 2007. In 2006 we had 9 students: three of these projects have resulted in completed libraries being added to the Boost project, and two of the students have become long term contributors. Five other projects were completed successfully, but the students ran out of time before polishing the library to a sufficient standard for Boost submission: none the less these represent significant bodies of work that will shape future development efforts in these areas. In 2007 we had a couple of students drop out, of the remaining 6 projects, one has been integrated into Boost and the student gone on to be a significant Boost contributor, three others have been under continued active development through last Autumn - we hope to tempt more students back once their college commitment allows. 6) If your organization has not previously participated in GSoC, have you applied in the past? If so, for what year(s)? (optional) Nothing to say here 7) What license does your project use? The Boost Software License: http://www.boost.org/LICENSE_1_0.txt See also: http://opensource.org/licenses/bsl1.0.html 8) URL for your ideas page http://www.crystalclearsoftware.com/cgi-bin/boost_wiki/wiki.pl?Google_Summe… 9) What is the main development mailing list for your organization? http://www.boost.org/more/mailing_lists.htm#main 10) Where is the main IRC channel for your organization? http://www.boost.org/more/mailing_lists.htm#IRC 11) Does your organization have an application template you would like to see students use? If so, please provide it now. (optional) Introduction: Introduce the main concepts around the project: Theoretical preliminaries, pre-existing Boost libraries used (if any), important concepts, problems/needs the project will try to solve/satisfy. Goal: Concise statement of the overall goal of the project. Refine this initial statement to include: project deliverables (code, docs, testing), required/suggested methodology, standards of quality, possible goal extensions beyond the main objective. Requirements: List the requirements and level of expertise you estimate the student will have to meet: Required level of C++, specific areas of the language (STL, templates, locales, whatever), level of familiarity with Boost and particular Boost libraries, development/documentation/testing tools, mathematical/algorithmic background, other desirable skills. Other sections: If you have more to say about the project that doesn't fit in the proposed sections of this template, feel free to add other sections at will. Oh, and don't forget to separate each entry with a horizontal line, entered at the edit box as ---- 12) Who will be your backup organization administrator? Please enter their Google Account address. We will email them to confirm, your organization will not become active until they respond. (optional) jz.maddock(a)gmail.com Mentors ~~~~~~~~ 1) What criteria did you use to select these individuals as mentors? Please be as specific as possible. We only use existing Boost library authors as mentors: people who have been through the Boost submission process already and know their way around the project. Ultimately the moderators of the Boost library project have final say on who acts as a mentor - our aim is to seek out the existing authors with the best development practices and persuade them to mentor! 2) Who will your mentors be? Please enter their Google Account address separated by commas. If your organization is accepted we will email each mentor to invite them to take part. (optional) TODO: Mentor list here!!!! About the program ~~~~~~~~~~~~~~~~~ 1) What is your plan for dealing with disappearing students? Whilst we have to accept that ultimately some students will be bound to drop out, we do try and avoid this as far as is possible. In the application process we look for enthusiasm, communications skills, and community participation as well as technically good applications: if we are able to select students who "can't wait to start" then that tends to reduce the initial dropout rate. Once the project starts we try and ensure that the students have regular contact with their mentors and plenty of help and encouragement to continue where required: while still trying to ensure that the students have the opportunity to explore and grow into the project and explore their own ideas. This is a fine line to draw, and one we will no doubt never get completely resolved! 2) What is your plan for dealing with disappearing mentors? We've never had a mentor disappear, but in the last two years we ended up with more mentors than students, so if necessary we have had backup mentors available. We also have a dedicated mailing list for the students: useful if they need a response faster than their mentor can provide. In the event of a student/mentor dispute then the Boost moderators are available to help resolve things - thankfully we haven't needed that so far. 3) What steps will you take to encourage students to interact with your project's community before, during and after the program? We encourage students to interact on the mailing list and discuss and refine project ideas prior to submission: in the past this has resulted in much improved project submissions, and a reasonable indicator of which students are likely to continue this interaction during and after the project. 4) What will you do to ensure that your accepted students stick with the project after GSoC concludes? As well as encouragement to continue, we try to provide students with detailed feedback on their progress towards getting their contributions formally accepted into Boost, so that they know exactly what needs to be done to complete the project. Although progress after the SOC period ends tends to be slow - we still have SOC 2006 projects being actively worked on - none the less we have been pleased with the continuing involvement of past students.

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Re: [boost] Proto expresion construction question
by Eric Niebler 10 Mar '08

10 Mar '08

Cédric Venet wrote: > Hi, > > I decided to try to write a small vector library with proto to test it. > > The following worked without problem (I will use extend further on but at > the moment the as_expr are needed) > > proto::display_expr( proto::as_expr(x)+proto::as_expr(y)*proto::as_expr(z) > , std::cout ); > > I then added > > struct fastvec_reduction_tag {}; > struct sum_ {}; > template<typename A> > typename proto::result_of::make_expr< > fastvec_reduction_tag > // , MixedDomain > , sum_ const > , A const & >> ::type sum(A const &a) { > return proto::make_expr<fastvec_reduction_tag/*, MixedDomain*/>(sum_(), > boost::ref(a)); > } > > Which work well > > proto::display_expr( sum(x) , std::cout ); > > And now, I would like to create a "function" dot(x,y) which expand to > sum(x*y). > I tried: > > template<typename A, typename B> > typename proto::result_of::make_expr< > fastvec_reduction_tag > // , MixedDomain > , sum_ const > , BOOST_TYPEOF(boost::ref(proto::as_expr(A())*proto::as_expr(B()))) >> const & >> ::type dot(A const &a, B const &b) { > return proto::make_expr<fastvec_reduction_tag/*, MixedDomain*/>(sum_(), > boost::ref( > proto::as_expr(a)*proto::as_expr(b) > )); > } > > Which compile but fail at runtime when I do > > proto::display_expr( dot(x,y) , std::cout ); > > (it call << on an invalid vector (type of x and y)). > > Is there a ways to create the tree for sum(x*y) directly or should I use a > transform (create a tree with a dot tag and then transform it with proto)? The problem you're running into is that as_expr(a) is creating a temporary object, which is getting held by reference in the expression tree created by proto's operator* overload. Then you're returning the tree and letting the references dangle. When creating trees and returning them from functions, you should be using make_expr() consistently so that you have explicit control over what gets stored by reference and by value. Try this: #include <iostream> #include <boost/xpressive/proto/proto.hpp> #include <boost/xpressive/proto/debug.hpp> using namespace boost; struct fastvec_reduction_tag {}; struct sum_ {friend std::ostream&operator<<(std::ostream&s,sum_){return s<<"sum_";}}; template<typename A> typename proto::result_of::make_expr< fastvec_reduction_tag , sum_ const , A const & >::type sum(A const &a) { return proto::make_expr<fastvec_reduction_tag>( sum_() , boost::ref(a) ); } template<typename A, typename B> typename proto::result_of::make_expr< fastvec_reduction_tag , sum_ const , typename proto::result_of::make_expr< proto::tag::multiplies , A const & , B const & >::type >::type dot(A const &a, B const &b) { return proto::make_expr<fastvec_reduction_tag>( sum_() , proto::make_expr<proto::tag::multiplies>( boost::ref(a) , boost::ref(b) ) ); } int main() { int x = 0, y = 1; proto::display_expr( sum(x) , std::cout ); proto::display_expr( dot(x,y) , std::cout ); return 0; } > The page 'users_guide\expression_construction\construction_utils.html' seems > very complete, but hard to understand how to put it in practice, perhaps you > could link it to some use in the example. This might make a good example, in fact. Thanks. -- Eric Niebler Boost Consulting www.boost-consulting.com

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