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[iostreams] patch for close(sink, in|out)
by Takeshi Mouri 03 Aug '06

03 Aug '06

Hello, I noticed that there is a problem in treating the parameter "which" on iostreams::close(). So, the following code doesn't output anything to standard output. #include <boost/iostreams/categories.hpp> #include <boost/iostreams/close.hpp> #include <iostream> namespace io = boost::iostreams; class test_sink { public: typedef char char_type; struct category : io::output, io::device_tag, io::closable_tag {}; std::streamsize write(const char*, std::streamsize n) { return n; } void close() { std::cout << "called test_sink::close()" << std::endl; } }; int main() { test_sink sink; // doesn't call test_sink::close() io::close(sink, BOOST_IOS::in|BOOST_IOS::out); } OTH, some device adapters in Boost.Iostreams perform such function call for closing the external device. Such the adapters never close the external device. The attachment is a patch for this problem. Regards, Takeshi Mouri

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Re: [boost] Portable signbit macro/function?
by Martin Bonner 03 Aug '06

03 Aug '06

----Original Message---- From: boost-bounces(a)lists.boost.org [mailto:boost-bounces@lists.boost.org] On Behalf Of Johan Råde Sent: 03 August 2006 12:38 To: boost(a)lists.boost.org Subject: Re: [boost] Portable signbit macro/function? > John Maddock wrote: > >> And the endianness of the float's if you're doing bit testing. But >> of course if there is a macro already it's easy enough to convert it >> into a function. > > The following function does bit testing, without advance knowledge of > which bit is the sign bit. The function figures out on its own, at > compile time, which bit is the sign bit. Hence you do not have to > worry > about IEEE 754 and endianness. The only thing that is required is that > sizeof(float) == sizeof(int). It also requires that the sign bit of the float is in the same place as the sign bit of the int ... which it is for most usual implementations of IEEE 754 (although I'm not sure if the standard actually refers to byte ordering issues), but I don't think it is true for Vax floating point formats. > > bool signbit(float x) > { > const float one = 1; > const float neg_one = -1; > const int sign_mask = reinterpret_cast<const int&>(one) > ^ reinterpret_cast<const int&>(neg_one); > return reinterpret_cast<int&>(x) & sign_mask; > } > > I have tested it on VC++ 7.1 with signed zeroes, signed infinities and > signed NaNs, and plain signed numbers. Can I suggest that you study the tenth commandment for C programmers at http://www.lysator.liu.se/c/ten-commandments.html. C++ avoids the need for some of those commandments, but that one has stood the test of time with undiminished force. -- 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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[ublas] Serious bug in mapped_vector_of_mapped_vector
by Matthias Troyer 03 Aug '06

03 Aug '06

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 Best regards Matthias #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); }

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[Boost-bugs] [ boost-Bugs-1533595 ] serializing empty vectors triggers STL assertion failure (VC
by SourceForge.net 03 Aug '06

03 Aug '06

Bugs item #1533595, was opened at 2006-08-03 04:39 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=1533595&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: serialization Group: None Status: Open Resolution: None Priority: 5 Submitted By: Thomas Pintaric (pintaric) Assigned to: Robert Ramey (ramey) Summary: serializing empty vectors triggers STL assertion failure (VC Initial Comment: Serializing empty vectors triggers an STL assertion failure (VC++ 8.0). Test case: ========== typedef std::vector<int> vec_t; vec_t v; // empty vector { std::ofstream ofs("test.dat"); boost::archive::binary_oarchive oa(ofs); oa << v; // triggers runtime assertion } The assertion is caused by line 31 in serialization/detail/get_data.hpp (note that vector v is empty): [0031] return &(v[0]); Proposed fix: ============= Index: oarchive.hpp =================================================================== RCS file: /cvsroot/boost/boost/boost/archive/array/oarchive.hpp,v retrieving revision 1.3 diff -r1.3 oarchive.hpp 73c73 < * this->This() << serialization::make_array(serialization::detail::get_data(t),t.size()); --- > if(count) * this->This() << serialization::make_array(serialization::detail::get_data(t),t.size()); Index: iarchive.hpp =================================================================== RCS file: /cvsroot/boost/boost/boost/archive/array/iarchive.hpp,v retrieving revision 1.3 diff -r1.3 iarchive.hpp 77c77 < * this->This() >> serialization::make_array(serialization::detail::get_data(t),t.size()); --- > if(count) * this->This() >> serialization::make_array(serialization::detail::get_data(t),t.size()); ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=107586&aid=1533595&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] library for type erasure
by Steven Watanabe 02 Aug '06

02 Aug '06

AMDG Alexander, > >Steven, do you have a document that describes your approach in more details? Does it support multimethods for binary operations? > >-- >Alexander Nasonov > > No I don't have such a document so here are the main benefits and drawbacks of my approach. I didn't know about your library until yesterday so I only understand it in general but I will try to primarily note the differences: I am using a table of function pointers and an unchecked variant type(like Boost.Function) instead of using virtual functions. Thus I avoid a heap allocation for objects that are small enough and are correctly aligned. On the other hand this implementation requires the cast methods to only convert to the exact type put in - not to any of it's base classes. The class template erasure is declared as template<class Operations, class Policy = default_policy, class Derived = my_own_type> class erasure; Operations is a composite tree of operations to allow groups of operations to behave the same as single operations. So all three of these are equivalent typedef combine_operations<boost::mpl::vector<isreamable, ostreamable> > ops; erasure<ops> any; typedef combine_operations<istreamable> ops; erasure<boost::mpl::vector<ops, ostreamable> > any; erasure<boost::mpl::vector<isreamable, ostreamable> > any; Policy specifies the details of the object structure. I have implemented a policy that simulates a virtual function based approach but this seems to put excessive strain on the compiler because of the extra dependencies it introduces. Derived is to allow members like assignment which return(*this) to cast to the correct type. Because of the two other parameters I don't allow things like erasure<istreamable, ostreamable> like of Boost.Variant although I think I could add support for it(with some ugly metafunctions and more coupling). I have provided support for Boost.Ref int i; erasure<...> any(boost::ref(i)); int& iref = erasure_cast<int&>(any); assert(&i == &iref); const int* iptr = erasure_cast<const int*>(*any); assert(iptr == & iref); The price of allowing the addition of const(or volatile) is a very repetitive section of code and 1-2 extra integer comparisons. One final optimization I have implemented is for conversions from one type to a subset. I think that this will slow down the assignment(especially in a multi-threaded program) but will speed up subsequent operations on the result. erasure<istreamable, ostreamable> any_io(1); erasure<ostreamable> any_out(any_io); assert(erasure_cast<const int&>(any_out) == 1); I do not support multi-methods. Unfortunately, there is no way to implement a binary operation that takes two arbitrary types. The closest I can get is to have an operation that takes one arbitrary type and one type from some fixed set which may depend on the first type. I didn't even think of this possibility until you mentioned it so I havn't actually tried to implement it. Finally, here is an example of how I am defining operations: struct addition1 : operation<addition1> { template<class T, class Any> struct static_impl : implementation<void (T&, const Any&)> { static void execute(T& arg, const Any& other) { arg += erasure_cast<const T&>(other); //throws bad_erasure_cast } }; template<class Base> struct partial_interface : Base { typename Base::erasure_full_t& operator+=(const typename Base::erasure_full_t& other) { erasures::call<addition1>(*this, other); //throws object_is_empty return(*erasures::full(this)); } }; }; From the above you can see that the syntax for defining operations is somewhat less than ideal. The main problem I know of is that defining overloaded functions requires a workaround to prevent the derived class version from hiding the base class one. Thus the preceeding example becomes: struct addition1 : operation<addition1> { template<class T, class Any> struct static_impl : implementation<void (T&, const Any&)> { static void execute(T& arg, const Any& other) { arg += erasure_cast<const T&>(other); } }; template<class Base> struct partial_interface_impl : Base { typename Base::erasure_full_t& operator+=(const typename Base::erasure_full_t& other) { erasures::call<addition1>(*this, other); return(*erasures::full(this)); } }; template<class Base> struct partial_interface : partial_interface_impl<Base> { using partial_interface_impl<Base>::operator+=; }; }; If you have any furthur questions I would be glad to answer them. In Christ, Steven Watanabe

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Re: [boost] Boost.Operators base class chaining
by Steven Watanabe 02 Aug '06

02 Aug '06

AMDG Daniel, > >Sure, but this a known and solved problem. Just use addable1 directly, >as documented in the "Caveat" at ><http://boost.org/libs/utility/operators.htm#chaining>. > I guess I should have read the documentation more carefully. Thank you again. In Christ, Steven Watanabe

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[filesystem] very minor request
by Gennaro Prota 02 Aug '06

02 Aug '06

Hi, I don't know if this has been discussed in the LWG but I'd like to make basic_path(const string_type& s); // (*) explicit. I'm right now working on the inspect tool, trying to cut down some of its dependencies. After eliminating boost::bind, which looks overkill to me in this case, I came upon a ironical situation: I modified the function contains_dot() to take a reference to path instead of a reference to string. The intent was to have a stricter type checking: bool contains_dot( /*std::string const& x */ path const & p) { return p.string().find( '.' ) != std::string::npos; } On the invoking code however, I forgot to remove ".string()", so I was still passing a string to it, except that the converting constructor (*) made everything compile anyway. As a result I was converting the path twice, from string and then again to string. This doesn't seem an unusual situation to me, especially when refactoring. What do you think? -- [ Gennaro Prota, C++ developer for hire ]

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[endian] Comments on Endian 0.5
by Dave Dribin 02 Aug '06

02 Aug '06

Hello, I started a thread on Boost-users about the proposed endian library, but it's probably more suitable on the dev list. Here's a link to the thread in the archives: <http://lists.boost.org/boost-users/2006/07/20887.php> I see two issues with the library as of 0.5. First, the endian classes cannot be used in unions. And, second the classes cannot be used in variable argument lists. I'm attaching a patch to help resolve both of these issues. In order to be used in a union, a class must not have any constructors. However, removing constructors breaks the following code: big4_t x = 42; My solution was to provide a static init() method to help in these situations: big4_t x = big_t::init(42); The second problem shows up using varargs. For example, this will not compile: printf("x = %d\n", x); The solution I came up with is to use operator() to get the native value: printf("x = %d\n", x()); In my patch, I've also added a check_unions() function to endian_test.cpp that tests the sizes of unions. Thanks, -Dave

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interest in sorted vector containers?
by Lewis Hyatt 02 Aug '06

02 Aug '06

Hi Everyone- Is there any interest in providing Boost container classes with the same functionality as set/map implemented with sorted vectors? I have four simple classes vset, vmap, vmultiset, vmap which do this. It seems like it would be quite useful, especially since, in my experience, set and map are heavily overused because of their convenience even when the insertion efficiency and iterator invalidation guarantees are not necessary. My classes provide the same interface as the STL equivalent, with additional functions such as nth_element() that take advantage of the random access iterators, and some conveniences like key-only and value-only iterators for vmap and vmultimap. I can post the code with a first attempt at making it appropriate for Boost if people think it is worth it? -Lewis

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Is there any interest in a UTF-8 library?
by Nemanja Trifunovic 02 Aug '06

02 Aug '06

Hello everybody. I have just released Beta 2 version of a small (one header file) generic library for handling UTF-8 encoded strings - you can read more about it at http://utfcpp.sourceforge.net/ . Is there any interest in adding this library too Boost? Either as a separate library or maybe as an addition to some of existing ones. Thanks. Nemanja Trifunovic --------------------------------- See the all-new, redesigned Yahoo.com. Check it out.

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