July 2006 - Boost - lists.preview.boost.org

Re: [boost] boost::bind dilemma
by Sohail Somani 25 Jul '06

25 Jul '06

> -----Original Message----- > From: boost-bounces(a)lists.boost.org > [mailto:boost-bounces@lists.boost.org] On Behalf Of Michael Goldshteyn > Sent: Tuesday, July 25, 2006 8:33 AM > To: boost(a)lists.boost.org > Subject: [boost] boost::bind dilemma > > I have an interesting dilemma in my usage of boost::bind. Consider: > [snip lots of bind statements] At this point you might be better off writing your own loop. I personally draw the line at multi-line bind statements with stl algorithms - not as a moral issue or anything :)

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boost::bind dilemma
by Michael Goldshteyn 25 Jul '06

25 Jul '06

I have an interesting dilemma in my usage of boost::bind. Consider: --- // Definitions class Key; class BigValue { public: const Key &GetKey() const; }; class MyMap { public: void Insert(const Key &k, const BigValue &v); }; // Usage void foo() { std::vector<BigValue> lotsOfValues; // Populate lots of values... ... // Transfer those values to the map, using the keys which are within the values MyMap myMap; // The transfer and also, the dilemma // Solution 1 std::for_each( lotsOfValues.begin(), lotsOfValues.end(), boost::bind( MyMap::Insert, // The function used to insert boost::ref(myMap), // The map into which we are inserting the keys/values boost::bind(BigValue::GetKey,_1), // The function to be called to extract the key from the value _1 ) ); } --- OK, this compiles and works, but the fourth parameter to the outer bind, _1, must be copied each time an Insert takes place, from my understanding of how bind works. Since this is a "BigValue" and the Insert() function in MyMap takes a const reference as it's second parameter, I would like for it not to be copied. So, the solution becomes: // Solution 2 --- std::for_each( lotsOfValues.begin(), lotsOfValues.end(), boost::bind( MyMap::Insert, // The function used to insert boost::ref(myMap), // The map into which we are inserting the keys/values boost::bind(BigValue::GetKey,_1), // The function to be called to extract the key from the value boost::bind<const BigValue &>(boost::cref<BigValue>,_1) // Get at the value, without creating a temporary BigValue ) ); --- Well this sure looks overly complex. Shortcuts, such as the following, will not compile: // Invalid solution 3 --- std::for_each( lotsOfValues.begin(), lotsOfValues.end(), boost::bind( MyMap::Insert, // The function used to insert boost::ref(myMap), // The map into which we are inserting the keys/values boost::bind(BigValue::GetKey,_1), // The function to be called to extract the key from the value boost::cref(_1) // Attempt to use the cref directly, and let bind deduce the type (fails to compile) ) ); --- // Invalid solution 4 --- std::for_each( lotsOfValues.begin(), lotsOfValues.end(), boost::bind( MyMap::Insert, // The function used to insert boost::ref(myMap), // The map into which we are inserting the keys/values boost::bind(BigValue::GetKey,_1), // The function to be called to extract the key from the value boost::bind(boost::cref<BigValue>,_1) // Attempt to use the cref, deferred, and let bind figure out the resultant return type (fails to compile) ) ); --- Is there a simpler solution than Solution 2, above? Thanks, Michael Goldshteyn

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Misbehaviour of boost.regex
by Torsten Landschoff 25 Jul '06

25 Jul '06

Hi *, I think I stumbled across a bug in boost.regex, but perhaps it is just me misunderstanding the docs. Basically it seems like regex_match breaks its postcondition when working with std::string input and smatch result. Attached is a new test case for the test suite (my first trial, I bet it does not fit into boost unchanged) which shows the bug (if it is one). Interestingly, using regex_match together with a const char pointer and cmatch results works like expected. I attached the new source file, which belongs into boost/libs/regex/test/regress together with changes to the Jamfiles as a diff. Any comments welcome. Greetings Torsten

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[move semantics] Do we have any plan for move semantics emulation?
by Ion Gaztañaga 25 Jul '06

25 Jul '06

Hi to all, The rvalue reference is likely to be accepted for the next standard and the standard library is also likely to be modified to implement move semantics. Googling around, the only thing I've found related to Boost and move semantics is Jonathan Turkanis' Boost Move Ptr (http://www.kangaroologic.com/move_ptr/) This move ptr and Howard's unique_ptr emulation code (http://home.twcny.rr.com/hinnant/cpp_extensions/unique_ptr_03.html) are similar and offer a good new smart pointer. However, I was wondering if we could try to sketch an emulation of "std::move()" for objects that are not unique_ptr/move_ptr. Something that would allow at least to define (portably, perhaps with a macro that in the future, with compilers that implement move semantics, can be expanded to the proper && signature) move constructors and assignments: boost::movable_t movable_source(...); boost::movable_t movable_target(boost::move(movable_source)); We won't have perfect forwarding but we could start playing with move semantics to see how it feels. We would need an explicit move from temporaries, if rvalue catching can't be emulated: boost::movable_t produce_movable(); boost::movable_t movable_target(boost::move(produce_movable())); The idea would be to define some macros that would allow some kind of emulation and that would become proper rvalue references in future compilers: my_class(BOOST_NAMED_RVALUE_REF(my_class) move_src) : m_member(BOOST_NAMED_RVALUE_REF_GET(move_src).member) {} BOOST_RVALUE_REF might be a class holding a pointer to the move sourceand BOOST_RVALUE_REF_GET an operator returning a reference to the pointed object: #define BOOST_NAMED_RVALUE_REF(class_name) rvalue_emulation<class_name> #define BOOST_NAMED_RVALUE_REF_GET(object_name) (*object_name) in the future those would be expanded to: #define BOOST_NAMED_RVALUE_REF(class_name) class_name && #define BOOST_NAMED_RVALUE_REF_GET(object_name) object_name As far as know, only Codewarrior (don't know if an experimental version or officially released one) has move semantics implemented under an explicit pragma. I've read about efforts to implement this on gcc but I haven't heard anything recently. Does any booster ideas for emulating move semantics or is there any ongoing effort? I'm ready to help a bit about this, but I would want to know if I might be duplicating efforts. Regards, Ion

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[Boost-bugs] [ boost-Bugs-1528399 ] [program_options] Endless loop with long default arguments
by SourceForge.net 25 Jul '06

25 Jul '06

Bugs item #1528399, was opened at 2006-07-25 16:02 Message generated for change (Tracker Item Submitted) made by Item Submitter You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=107586&aid=1528399&group_… Please note that this message will contain a full copy of the comment thread, including the initial issue submission, for this request, not just the latest update. Category: None Group: None Status: Open Resolution: None Priority: 5 Submitted By: Enrico Scholz (ensc) Assigned to: Nobody/Anonymous (nobody) Summary: [program_options] Endless loop with long default arguments Initial Comment: when using a po::value with a representation of the default value having a certain length, 'std::cout << opts' will stuck in an endless loop. E.g. ----- #include <boost/program_options.hpp> #include <string> #include <iostream> namespace po = boost::program_options; int main(int argc, char *argv[]) { po::options_description opts; opts.add_options() ("cfgfile,c", po::value<std::string>()->default_value("/usr/local/etc/myprogramXXXXXXXXX/configuration.conf"), "the configfile"); std::cout << opts; } ----- | $ rpm -q boost | boost-1.33.1-5 | | $ g++ foo.c -lboost_program_options | $ strace ./a.out | ... | write(1, " -c [ --cfgfile ] arg (=/usr/lo"..., 80 -c [ --cfgfile ] arg (=/usr/local/etc/myprogramXXXXXXXXX/configuration.conf) | ) = 80 | write(1, " "..., 80 | ) = 80 | write(1, " "..., 80 | ) = 80 | ... Removing one 'X' will result in an ugly | -c [ --cfgfile ] arg (=/usr/local/etc/myprogramXXXXXXXX/configuration.conf) t | h | e | c | o | n | f | i | g | f | i | l | e output. It would be nice, when: - the default value could be moved into the description column - the description would begin on a new line and an earlier column (e.g. 30-40) when option name/default-value are too long (> 30-40 chars) ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=107586&aid=1528399&group_… ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys -- and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ Boost-bugs mailing list Boost-bugs(a)lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/boost-bugs

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Re: [boost] is_nan
by Martin Bonner 25 Jul '06

25 Jul '06

----Original Message---- From: Johan Råde > template<class T> bool is_nan(T a) > { > return a != a; > } > > > 1. Do these implementations work an all platforms? I believe is_nan is vunerable to over-eager optimizers for built-in types. > 2. The category not-a-number can be divided into the sub-categories > quite not-a-number and signalling not-a-number. ^^^^^ Should be "quiet". This error has continued throughout the email chain, so it is obviously not just a simple typo (or it is getting copy-and-pasted). -- Martin Bonner Martin.Bonner(a)Pitechnology.com Pi Technology, Milton Hall, Ely Road, Milton, Cambridge, CB4 6WZ, ENGLAND Tel: +44 (0)1223 203894

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multi-array problem
by Neal Becker 25 Jul '06

25 Jul '06

I ran into a problem using multi-array. Not really a "bug", but a bit of unexpected behavior. Most containers have constructors like: template<typename old_t> Container (old_t const&); Allows constructing the new container from any sequence - the new container will have a copy of the contents of the old (usually). If you try this with multi-array you will not get a compilation error, but also will not get anything like what you expected.

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Create a boost/algorithm/math sub-library?
by Daryle Walker 25 Jul '06

25 Jul '06

We have a general algorithms directory, currently with a subdirectory with string routines. I want to add a parallel subdirectory with math routines. The routines I want to add are for the Greatest Common Factor and the Least Common Multiple. Now, I already have a header for that in Boost at $ROOT/boost/math/common_factor_rt.hpp, but the main function and function object class templates in that header encapsulate the real implementation. It's those implementation functions that I want to public place in the algorithm collection. They would be: 1. GCD for unsigned numbers and other non-signed entities, like polynomials, using division & modulus reduction. 2. GCD for signed entities; similar to [1] but there are sign comparisons and possible negations, which types in [1] don't have to support. 3. GCD for binary unsigned integers using bit-level operations; it has the same complexity as [1] and [2], O(digit_count^2), but is generally faster because bit twiddling is faster than division. The wrapping code currently in the math libraries, and elsewhere, would be changed to call these routines. Would this require a full-blown review, a mini-review, or no review? Note that we currently do _not_ implement [3] anywhere in Boost (AFAIK). For the future, I envision algorithm/math to only hold function (templates) that compute specific ways to evaluate a relation of interest. Full blown wrapping functions and function objects, as well as types, would stay within the regular math libraries (and call the algorithms as needed). -- Daryle Walker Mac, Internet, and Video Game Junkie darylew AT hotmail DOT com

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Incorrect library naming in bbv2
by John Maddock 25 Jul '06

25 Jul '06

The current name mangling scheme in bbv2 still doesn't match bbv1 and the auto-linking code. In particular if I build a library as a dll with msvc it doesn't get a "-mt" part in the library name, even though all builds against the dll runtime *are* multithreaded in msvc. Thanks, John.

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[Boost-bugs] [ boost-Bugs-1528178 ] ublas: bug in mapped_vector_of_mapped_vector
by SourceForge.net 25 Jul '06

25 Jul '06

Bugs item #1528178, was opened at 2006-07-25 05:54 Message generated for change (Tracker Item Submitted) made by Item Submitter You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=107586&aid=1528178&group_… Please note that this message will contain a full copy of the comment thread, including the initial issue submission, for this request, not just the latest update. Category: None Group: None Status: Open Resolution: None Priority: 9 Submitted By: Matthias Troyer (troyer) Assigned to: Nobody/Anonymous (nobody) Summary: ublas: bug in mapped_vector_of_mapped_vector Initial Comment: There is a serious bug in the mapped_vector_of_mapped_vector spare matrix type. Rows containing only zero elements are not treated correctly in prod(). The following code should give a vector that contains only 1 in the last element. Instead prod() gives a vector containing 1 in each element. In debug mode this bug is found by the checks: Check failed in file boost/boost/numeric/ublas/detail/ vector_assign.hpp at line 371: detail::expression_type_check (v, cv) Aborted The bug appears in Boost 1.33 as well as in the CVS version #include <boost/numeric/ublas/matrix_sparse.hpp> #include <boost/numeric/ublas/vector.hpp> int main() { boost::numeric::ublas::mapped_vector_of_mapped_vector<double> m (64,64); boost::numeric::ublas::vector<double> v(64); boost::numeric::ublas::vector<double> w(64); v[63] = 1.; m(63,63) = 1.; w = boost::numeric::ublas::prod(m,v); } ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=107586&aid=1528178&group_… ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys -- and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ Boost-bugs mailing list Boost-bugs(a)lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/boost-bugs

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