May 2012 - Boost-users - lists.preview.boost.org

[Geometry] spatial linestring access along line
by Stephan Menzel 25 May '12

25 May '12

Hi all, before I begin, let me tell that geometry is not exactly my strong suite so please forgive my probably dumb question. I have started to work with boost geometry which, I find very neat, and assembled a line string. Now I basically need a method that gives me a point to a length value. Like when my linestring is 100 units long and I say give me the point at 3 I want the exact position of the point (coordinates) as if I were following the line for exactly 3 units. I have an approach that would allow me to implement this myself by following the segments (possibly after indexing them) but I have a feeling that one of those many functions provided by the library itself might do just that and I simply don't know it. If anyone knows if such is the case, would be nice to give me a heads up. Thanks, Stephan

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[multi_index] movable only types
by Szymon Gatner 25 May '12

25 May '12

Hi, with boost.move available are there any plans to make multi_index work with movable-only types? -- Szymon Gatner The Lordz Games Studio www.thelordzgamesstudio.com

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offlist - Re: [iterator] Problems with iterator_facade and const-qualification
by Neil Groves 24 May '12

24 May '12

On Sat, May 7, 2011 at 5:52 PM, Dave Abrahams <dave(a)boostpro.com> wrote: > On Fri, May 6, 2011 at 1:51 PM, Evan Driscoll <driscoll(a)cs.wisc.edu> > wrote: > > On 05/06/2011 11:59 AM, Jeff Flinn wrote: > >> > >> You might google any_iterator, and see how other authors have addressed > >> similar problems. > > > > Great! I tried to find someone who had done something similar, figuring I > > couldn't have been the first, but all the search terms I tried were too > > generic. > > > > Thanks, > > Evan > > You can find one in the ASL that's built on iterator_facade. > http://stlab.adobe.com/classadobe_1_1any__iterator.html > > The underlying Boost.Range implementation implements an any_iterator that I believe to be similar to the one in ASL in terms of functionality. I believe that the small-buffer optimization implementation is superior to forcing the definition of a closed-set of possible type as suggested in a TODO within the ASL documentation. During my performance testing I had considerably superior performance than the ASL implementation. I wondered if you disliked my implementation, or had any feedback. Additionally I wondered what you thought about moving the Boost.Range internal any_iterator implementation into Boost.Iterator. I can't honestly imagine a good use-case for using any_iterator in preference to any_range, hence I haven't suggested this previously. This could easily be due to my lack of imagination! Can you think of a time when using an any_iterator on any interface would be superior to using an any_range? Your opinions and guidance would be much appreciated. HTH, > > -- > Dave Abrahams > BoostPro Computing > http://www.boostpro.com Regards, Neil Groves

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Iterator concept checking
by McNamara, Nate 24 May '12

24 May '12

I'm trying to learn to use BOOST_CONCEPT_CHECK for custom iterators, ranges, and containers. I've built a simple linked list class with an iterator (and const_iterator) that, as far as I can tell, satisfies the forward traversal iterator requirements. However, g++ gives the following errors: concept.cpp:81: error: `*' cannot appear in a constant-expression concept.cpp:81: error: a call to a constructor cannot appear in a constant-expression concept.cpp:81: error: template argument 1 is invalid concept.cpp:81: error: template argument 1 is invalid concept.cpp:82: error: `*' cannot appear in a constant-expression concept.cpp:82: error: a call to a constructor cannot appear in a constant-expression concept.cpp:82: error: template argument 1 is invalid concept.cpp:82: error: template argument 1 is invalid concept.cpp:83: error: `*' cannot appear in a constant-expression concept.cpp:83: error: a call to a constructor cannot appear in a constant-expression concept.cpp:83: error: template argument 1 is invalid concept.cpp:83: error: template argument 1 is invalid concept.cpp:84: error: `*' cannot appear in a constant-expression concept.cpp:84: error: a call to a constructor cannot appear in a constant-expression concept.cpp:84: error: template argument 1 is invalid concept.cpp:84: error: template argument 1 is invalid Compiling with -E, lines 81-84 are as follows: typedef ::boost::concepts::detail::instantiate< &::boost::concepts::requirement_<void(*)(boost::concepts::ForwardTravers alIterator<iterator>)>::failed> boost_concept_check81; typedef ::boost::concepts::detail::instantiate< &::boost::concepts::requirement_<void(*)(boost::concepts::WritableIterat or<iterator>)>::failed> boost_concept_check82; typedef ::boost::concepts::detail::instantiate< &::boost::concepts::requirement_<void(*)(boost::concepts::ForwardTravers alIterator<const_iterator>)>::failed> boost_concept_check83; typedef ::boost::concepts::detail::instantiate< &::boost::concepts::requirement_<void(*)(boost::concepts::ReadableIterat or<const_iterator>)>::failed> boost_concept_check84; That tells me that, regardless of why g++ is having trouble, my iterator fails to satisfy the concept somehow. So I wrote some code (see my_naive_check, below) to try to figure out which requirement is failing, but my check code is missing the same thing as the iterator, because the check code runs fine. Any pointers much appreciated. // concept.cpp // What's wrong with the iterators? #include <cassert> #include <cstdlib> #include <iostream> #include <string> #include <boost/concept_check.hpp> #include <boost/iterator/iterator_concepts.hpp> #include <boost/iterator/iterator_facade.hpp> #include <boost/lambda/lambda.hpp> #include <boost/range/algorithm.hpp> template <typename T> class List { struct Node { Node(const T& value_, Node *next_): value(value_), next(next_) {} T value; Node *next; } *head; public: List(): head(0) {} ~List() { Node *node = head; while (node) { Node *tmp = node->next; delete node; node = tmp; } } void push_front(const T& value) { head = new Node(value, head); } class iterator: public boost::iterator_facade<iterator, T, boost::forward_traversal_tag> { public: iterator(): node(0) {} private: iterator(Node * const node_): node(node_) {} friend class List; friend class boost::iterator_core_access; T& dereference() const { return node->value; } bool equal(const iterator& rhs) const { return node == rhs.node; } void increment() { node = node->next; } Node *node; }; iterator begin() { return iterator(head); } iterator end() { return iterator(); } class const_iterator: public boost::iterator_facade<const_iterator, const T, boost::forward_traversal_tag> { public: const_iterator(): node(0) {} const_iterator(const iterator& old): node(old.node) {} private: friend class boost::iterator_core_access; const T& dereference() const { return node->value; } bool equal(const const_iterator& rhs) const { return node == rhs.node; } void increment() { node = node->next; } const Node *node; }; const_iterator begin() const { return const_iterator(head); } const_iterator end() const { return const_iterator(); } BOOST_CONCEPT_ASSERT((boost::concepts::ForwardTraversalIterator<iterator >)); BOOST_CONCEPT_ASSERT((boost::concepts::WritableIterator<iterator>)); BOOST_CONCEPT_ASSERT((boost::concepts::ForwardTraversalIterator<const_it erator>)); BOOST_CONCEPT_ASSERT((boost::concepts::ReadableIterator<const_iterator>) ); }; /* ForwardTraversalIterator must be SinglePassIterator IncrementableIterator Assignable Copy Constructible &r == &++r r++ *r++ == != difference_type DefaultConstructible iterator_traversal<X>::type => forward_traversal_tag */ void my_naive_check(List<std::string>& words) { typedef List<std::string>::iterator It; It it1 = words.end(); it1 = words.begin(); &it1 == &++it1; It it2 = it1++; std::string word = *it2++; assert(it1 == it2); assert(words.begin() != words.end()); It::difference_type distance = 0; It it3; boost::forward_traversal_tag tag = boost::iterator_traversal<It>::type(); } int main() { List<std::string> words; words.push_front("world"); words.push_front("Hello"); my_naive_check(words); boost::for_each(words, std::cout << boost::lambda::_1 << "\n"); return EXIT_SUCCESS; } ________________________________________ This E-Mail (including any attachments) may contain privileged or confidential information. 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boost::asio one connectio-per-thread
by Christer Borgqvist 24 May '12

24 May '12

Hello, is this a code appropriate? boost::asio::io_service io_service; tcp::acceptor a(io_service, tcp::endpoint(tcp::v4(),3080)); for (;;) { socket_ptr sock(new tcp::socket(io_service)); a.accept(*sock); emv_clientthread_ptr cli(new axf::server::server_socket(sock)); boost::thread t(boost::bind(&axf::server::server_socket::start, cli)); } appreciate any help. Christer

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[Chrono] Negative real time
by Wilfried Kirschenmann 23 May '12

23 May '12

Dear chrono maintainer team, Using the following example : int main(int argc, char **argv) { boost::chrono::process_real_cpu_clock::time_point start = boost::chrono::process_real_cpu_clock::now(); for ( long i = 0; i < 1000; ++i ) std::sqrt( 123.456L ); // burn some time Sleep(10000); //idle some time boost::chrono::process_real_cpu_clock::time_point end = boost::chrono::process_real_cpu_clock::now(); std::cout << end << std::endl; boost::chrono::process_real_cpu_clock::duration elapsed = (end - start); std::cout << "took real : " << elapsed << "nanoseconds\n"; return 0; } I obtain negative times. I run boost 1.49 win32 on Windows 7 x64 with Visual studio 2010. Studying the behavior of the timer, I think that the error is one of these : - process_real_cpu_clock::now() only stores the current time in a 32 bit integer instead of a 64 bit integer - time_points only prints the 32 lowest bits. I came to this conclusion by observing the results printed before they got negatives (printing in the loop with the sqrt): 2019000000 nanoseconds is the last value printed before getting negative. Is there any mistake in my way of using this chronometer ? Do you have a workaround ? Thank you for your help ! Wilfried K. ----- Cordialement, Wilfried Kirschenmann "An expert is a person who has made all the mistakes that can be made in a very narrow field."* *Niels Bohr - *Danish physicist (1885 - 1962)*

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boost::serialization "input stream error" in release-build (msvc2010)
by Jens Saathoff 23 May '12

23 May '12

Hi! I'm using boost::serialization to save a structure to a file and read from a file. My code works perfect in debug-build, but in release-build an exception is thrown. I'm using MSVC2010 to build the project on Windows 7 64-Bit-Machine. The code is the same. Who could help me out? You can find the code here: http://boost.codepad.org/8fp6XnC3 Thank you very much!!!!

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First attempt at using Boost::Test is a flop: the program ends with an exception related to std::string but I don't use any
by Ted Byers 23 May '12

23 May '12

Here is the full output from my program: $ ./decision.test.suite terminate called after throwing an instance of 'std::logic_error' what(): basic_string::_S_construct NULL not valid Aborted (core dumped) Now, all the code in this program is focussed on number crunching, so none of it involves strings. I am guessing that I missed something in setting up a test suite. After including the headers for the function objects being tested (some of which are template classes) as well as headers for several boost libraries, I have the following: #define BOOST_TEST_MAIN decision_tests #include <boost/test/unit_test.hpp> #include <boost/test/floating_point_comparison.hpp> BOOST_AUTO_TEST_SUITE( test_decisions ) BOOST_AUTO_TEST_CASE( test_dist_moments ) { And I have a series of test cases that start the same way. After setting up the required data for each test, I use something like: BOOST_CHECK_CLOSE( Sm, 0.00000000000, 0.0001 ); or something like: BOOST_CHECK(ibll(x1,i) == true); Of course each test case ends with a closing '}' and the whole program ends with: BOOST_AUTO_TEST_SUITE_END() Now, I know I can write a suite of unit tests without using Boost::Test, but I was hoping I'd just missed something obvious. I don't even know where to look for the cause of this exception since none of the code I actually wrote that is involved in these tests makes any use at all of any strings. My guess is that I must have missed some macro required by the unit test framework that is required in order to ensure whatever string object is involved in this exception doesn't get a NULL value. Or maybe I missed a header. I really have no idea where to look for the cause of this problem. Any guidance on what to look for or what I may have missed, would be greatly appreciated. Cheers Ted

6 7

boost::signals2::signal - is a "decimated" version available?
by Chris Stankevitz 22 May '12

22 May '12

Hi, I'm using boost::signals2::signal to notify a dialog when the state of an underlying object has changed. The signal is sometimes is generated at 100Hz. Other times it is generated at 1Hz. The dialog provides a "slot" for this signal that updates the controls on the screen. I'd like to limit the "slot rate" to 10Hz. By "slot rate" I mean the rate at which the slot receives notification from the signal. This will prevent the screen updates from happening faster than can be seen. Has this been done already? If not, I'm going to implement something like the pseudocode below. Currently I'm not sure how I to specify "arguments" nor how I am going to specify the function "SlotCallback". Thank you, Chris === Pseudocode: float MaxPeriod = 0.001; // 10Hz class SignalDecimator { public: void Register(signal Signal, slot Slot) { Signal.connect(&SignalDecimator::SlotCallback, this, _1, _2, _3, _4...); mSlot = Slot; } private: void SlotCallback(arguments Arguments) { if (TimeSinceLastCall() > MaxPeriod) { mSlot(Arguments); } else { mArguments = Arguments; if (!TimerIsRunning()) { StartTimer(MaxPeriod - TimeSinceLastCall()); } } } void TimerCallback() { mSlot(mArguments); } slot mSlot; timer mTimer; arguments mArguments; }

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Re: [Boost-users] asio - improving chat server example
by Marat Abrarov 22 May '12

22 May '12

Hi, John. > As you recall, I am using boost/Threads to execute io_service::run() to allow my server to have a > main-thread application loop. The use of threads have complicated my application design by giving me > problems to join the thread_group upon shutdown. > > I just had the thought, maybe I can tickle the io_service each frame of my main-thread loop instead of > using Threads? Is that the motivation for io_service::poll() ? Maybe using io_service.poll() will > allow me to avoid the need for threads, at least while I'm proving the concept. What do you think? I don't think asio::io_service::poll() can help you. The only solutions I can suggest I've described before. It isn't related to Asio - it is related to proactor pattern. > Maybe I can contribute a more interesting TCP server example if this works. :) Ideally, it would also > show clean shutdown when using threads to run the io_service, but I'm not there yet. I thought I've already done it :) > Also, I began looking at your code. Thank you for making it available. I'm a little worried it will > take me as long to learn your framework as it will to learn the Asio framework. It is not a framework. It is more like to be code snippets. Some parts are copies of Asio internals. Regards, Marat Abrarov.

2 1

Re: [Boost-users] Boost/Asio short read error
by Marcin Głogowski 22 May '12

22 May '12

Windows 7 64 bit ultimate, boost 1.49, examples from: http://www.stderr.org/doc/libasio-doc/examples/ssl_client_cpp.html http://www.stderr.org/doc/libasio-doc/examples/ssl_server_cpp.html Currently SSL works great, but several days ago I had many times "short read" error. Best regards Marcin > What boost/asio version do you use? What's your platform? What > specific example are you talking about? >> I have problem with Boost/asio - sometimes server returns "short read" >> error. >> I'm using client/server from the examples. >> Please write me - is it a bug or just wrong implemented example because the >> error occurs not every time. >> How to protect my application against the error? Dom Maklerski Banku Ochrony Środowiska Spółka Akcyjna ul. Marszałkowska 78/80 / 00-517 Warszawa wpisana w Rejestrze Przedsiębiorców prowadzonym przez Sąd Rejonowy dla m. st. Warszawy XII Wydział Gospodarczy Krajowego Rejestru Sądowego pod numerem: KRS 0000048901 / NIP 526-10-26-828 Kapitał zakładowy w wysokości 21.551.200zł wpłacony w całości. P - Nie drukuj tej wiadomości, jeśli to nie jest konieczne.

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[1.49][filesystem] problem while instantiating a global bfs::path variable
by Jan Boehme 22 May '12

22 May '12

Hello, using a global path variable as in the following sample is no longer possible when using 1.49 under Windows: #include <iostream> #include <boost/filesystem.hpp> boost::filesystem::path global_path("."); int main() { std::cout << global_path << std::endl; return 0; } The program crashes while starting. The following backtrace was captured: > msvcp100d.dll!std::codecvt<wchar_t,char,int>::in(int & _State=0, const char * _First1=0x00000000002af760, const char * _Last1=0x00000000002af761, const char * & _Mid1=0x0000000000000000, wchar_t * _First2=0x00000000002af460, wchar_t * _Last2=0x00000000002af660, wchar_t * & _Mid2=0x0000000000000000) Line 1521 + 0x5 bytes C++ > global_path.exe!`anonymous namespace'::convert_aux(const char * from=0x00000000002af760, const char * from_end=0x00000000002af761, wchar_t * to=0x00000000002af460, wchar_t * to_end=0x00000000002af660, std::basic_string<wchar_t,std::char_traits<wchar_t>,std::allocator<wchar_t> > & target="", const std::codecvt<wchar_t,char,int> & cvt={...}) Line 84 + 0x5a bytes C++ > global_path.exe!boost::filesystem3::path_traits::convert(const char * from=0x00000000002af760, const char * from_end=0x00000000002af761, std::basic_string<wchar_t,std::char_traits<wchar_t>,std::allocator<wchar_t> > & to="", const std::codecvt<wchar_t,char,int> & cvt={...}) Line 167 C++ > global_path.exe!boost::filesystem3::path_traits::dispatch<std::basic_string<wchar_t,std::char_traits<wchar_t>,std::allocator<wchar_t> > >(const std::basic_string<char,std::char_traits<char>,std::allocator<char> > & c=".", std::basic_string<wchar_t,std::char_traits<wchar_t>,std::allocator<wchar_t> > & to="", const std::codecvt<wchar_t,char,int> & cvt={...}) Line 174 + 0x9e bytes C++ > global_path.exe!boost::filesystem3::path::path<char const [2]>(const char [2]& source=0x000000013fa435d4, void * __formal=0x0000000000000000) Line 135 + 0x2d bytes C++ > global_path.exe!`dynamic initializer for 'global_path''() Line 4 + 0x1a bytes C++ > msvcr100d.dll!_initterm(void (void)* * pfbegin=0x000000013fa433d0, void (void)* * pfend=0x000000013fa43418) Line 873 C > global_path.exe!__tmainCRTStartup() Line 474 C > global_path.exe!mainCRTStartup() Line 371 C > kernel32.dll!000000007695652d() > [Frames below may be incorrect and/or missing, no symbols loaded for kernel32.dll] > ntdll.dll!0000000076dec521() The program was built using boost 1.49 under Windows 7 and MSVC 10. The same sample works as expected using Boost 1.48 while keeping the rest untouched. Thanks for clarification, Jan.

2 2

[iostreams] Memory mapped file resize
by Vitaly Budovski 22 May '12

22 May '12

Hello, It appears that the implementation of mapped_file in iostreams does have a resize method, but it isn't documented. If I'm going to be resizing a mapped_file_sink, are there any issues I need to be aware of? Particularly around the use of iterators. Thanks.

1 0

Rational: [PATCH] Eliminate excessive calls to gcd and add operator%
by Mario Lang 22 May '12

22 May '12

Hi. I am using boost/rational.hpp in my code to represent musical time with rational numbers. I have found some possible improvements. These improvements have accumulated into a small patch which I'd like to present for review. I think it is worth applying. There doesn't appear to be a maintainer for rational.hpp though, so I am writing to the list. The story: In my application I need a remainder operation. Looking at rational.hpp and its work-horse operators.hpp it became rather obvious that rational.hpp can and (in my opinion) should implement operator%= and friends. operator%= can easily be defined as return operator-= (other * rational_cast<int_type>(*this / other)); I have been using this definition for operator%= successfully in my code for quite a while. During a profiling session it showed up which made me think a bit more. Actually, the current way how rational.hpp implements mixed-mode operators is a waste of performance. It calls the corresponding operator with a temporary rational where the denominator is always equal to 1. However, this means that there are excessive (unnecessary) calls to boost::math::gcd performed by the operators. For instance, addition of two rational numbers needs two calls to gcd. On the other hand, addition of a rational number and an integer can be performed without any gcd at all (n += d * i). Similarily, multiplication of two rational numbers needs two calls to gcd, while multiplication of a rational with an integer only needs one call to gcd. So it is definitely worth it to actually define the mixed mode operators not in terms of the already existing operators but reimplement them with the unnecessary calls to gcd removed. After this, the definition of operator%=(const rational&) results in one less call to gcd (because there is one mixed-mode multiplication involved) and the definition of operator%=(param_type) saves two unnecessary calls to gcd since there is one mixed-mode multiplication and one mixed-mode division involved. Obviously, all code that involves mixed-mode operators benefits from these changes. As a side effect of reading code I noticed that the definition of operator=(param_type) (assign from an integer) also does unnecessary gcd. It currently calls assign(n, 1) which itself calls normalize() which does gcd. However, as above, we know that there is no need to calculate gcd of (n, 1) since it will always be 1. So I changed the definition of operator=(param_type) to directly assign the parameter to num and set den to 1, instead of calling assign(). Another useless call of gcd squashed! On top of these, we can observe that now that boost::rational provides operator%= it is actually an instance of ordered_euclidean_ring_operators. Comments and committers welcome. Index: rational.hpp =================================================================== --- rational.hpp (Revision 78523) +++ rational.hpp (Arbeitskopie) @@ -21,6 +21,7 @@ // Nickolay Mladenov, for the implementation of operator+= // Revision History +// 05 May 12 Add operator% and reduced use of implicit gcd (Mario Lang) // 05 Nov 06 Change rational_cast to not depend on division between different // types (Daryle Walker) // 04 Nov 06 Off-load GCD and LCM to Boost.Math; add some invariant checks; @@ -105,23 +106,10 @@ template <typename IntType> class rational : - less_than_comparable < rational<IntType>, - equality_comparable < rational<IntType>, - less_than_comparable2 < rational<IntType>, IntType, - equality_comparable2 < rational<IntType>, IntType, - addable < rational<IntType>, - subtractable < rational<IntType>, - multipliable < rational<IntType>, - dividable < rational<IntType>, - addable2 < rational<IntType>, IntType, - subtractable2 < rational<IntType>, IntType, - subtractable2_left < rational<IntType>, IntType, - multipliable2 < rational<IntType>, IntType, - dividable2 < rational<IntType>, IntType, - dividable2_left < rational<IntType>, IntType, - incrementable < rational<IntType>, - decrementable < rational<IntType> - > > > > > > > > > > > > > > > > + ordered_euclidean_ring_operators < rational<IntType>, + ordered_euclidean_ring_operators2 < rational<IntType>, IntType, + unit_steppable < rational<IntType> + > > > { // Class-wide pre-conditions BOOST_STATIC_ASSERT( ::std::numeric_limits<IntType>::is_specialized ); @@ -141,7 +129,7 @@ // Default copy constructor and assignment are fine // Add assignment from IntType - rational& operator=(param_type n) { return assign(n, 1); } + rational& operator=(param_type i) { num = i; den = 1; return *this; } // Assign in place rational& assign(param_type n, param_type d); @@ -155,15 +143,17 @@ rational& operator-= (const rational& r); rational& operator*= (const rational& r); rational& operator/= (const rational& r); + rational& operator%= (const rational& r); - rational& operator+= (param_type i); - rational& operator-= (param_type i); + rational& operator+= (param_type i) { num += i * den; return *this; } + rational& operator-= (param_type i) { num -= i * den; return *this; } rational& operator*= (param_type i); rational& operator/= (param_type i); + rational& operator%= (param_type i); // Increment and decrement - const rational& operator++(); - const rational& operator--(); + const rational& operator++() { num += den; return *this; } + const rational& operator--() { num -= den; return *this; } // Operator not bool operator!() const { return !num; } @@ -205,6 +195,14 @@ void normalize(); }; +// Type conversion +template <typename T, typename IntType> +inline T +rational_cast(const rational<IntType>& r BOOST_APPEND_EXPLICIT_TEMPLATE_TYPE(T)) +{ + return static_cast<T>(r.numerator()) / static_cast<T>(r.denominator()); +} + // Assign in place template <typename IntType> inline rational<IntType>& rational<IntType>::assign(param_type n, param_type d) @@ -327,50 +325,54 @@ return *this; } -// Mixed-mode operators template <typename IntType> inline rational<IntType>& -rational<IntType>::operator+= (param_type i) +rational<IntType>::operator%= (const rational<IntType>& r) { - return operator+= (rational<IntType>(i)); + return operator-= (r * rational_cast<IntType>(*this / r)); } +// Mixed-mode operators template <typename IntType> inline rational<IntType>& -rational<IntType>::operator-= (param_type i) -{ - return operator-= (rational<IntType>(i)); -} - -template <typename IntType> -inline rational<IntType>& rational<IntType>::operator*= (param_type i) { - return operator*= (rational<IntType>(i)); + // Avoid overflow and preserve normalization + IntType gcd = math::gcd(i, den); + num *= i / gcd; + den /= gcd; + + return *this; } template <typename IntType> -inline rational<IntType>& +rational<IntType>& rational<IntType>::operator/= (param_type i) { - return operator/= (rational<IntType>(i)); -} + // Avoid repeated construction + IntType const zero(0); -// Increment and decrement -template <typename IntType> -inline const rational<IntType>& rational<IntType>::operator++() -{ - // This can never denormalise the fraction - num += den; + if (i == zero) throw bad_rational(); + if (num == zero) return *this; + + // Avoid overflow and preserve normalization + IntType const gcd = math::gcd(num, i); + num /= gcd; + den *= i / gcd; + + if (den < zero) { + num = -num; + den = -den; + } + return *this; } template <typename IntType> -inline const rational<IntType>& rational<IntType>::operator--() +inline rational<IntType>& +rational<IntType>::operator%= (param_type i) { - // This can never denormalise the fraction - num -= den; - return *this; + return operator-= (i * rational_cast<IntType>(*this / i)); } // Comparison operators @@ -477,12 +479,7 @@ template <typename IntType> bool rational<IntType>::operator> (param_type i) const { - // Trap equality first - if (num == i && den == IntType(1)) - return false; - - // Otherwise, we can use operator< - return !operator<(i); + return operator==(i)? false: !operator<(i); } template <typename IntType> @@ -583,24 +580,13 @@ return os; } -// Type conversion -template <typename T, typename IntType> -inline T rational_cast( - const rational<IntType>& src BOOST_APPEND_EXPLICIT_TEMPLATE_TYPE(T)) -{ - return static_cast<T>(src.numerator())/static_cast<T>(src.denominator()); -} - // Do not use any abs() defined on IntType - it isn't worth it, given the // difficulties involved (Koenig lookup required, there may not *be* an abs() // defined, etc etc). template <typename IntType> inline rational<IntType> abs(const rational<IntType>& r) { - if (r.numerator() >= IntType(0)) - return r; - - return rational<IntType>(-r.numerator(), r.denominator()); + return r.numerator() >= IntType(0)? r: -r; } } // namespace boost -- CYa, ⡍⠁⠗⠊⠕

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Problem compiling with boost thread
by Rajalakshmi Iyer 21 May '12

21 May '12

Hello, I am trying to compile my application with Boost thread library (1.49.0) on Ubuntu 11.10 (gcc 4.6.1). However I see this error: $(BOOST_PATH)/include/boost/thread/detail/config.hpp:29:24: fatal error: platform.hpp: No such file or directory compilation terminated. In the file $(BOOST_PATH)/include/boost/thread/detail/config.hpp, the platform.hpp is included as: #include "platform.hpp" If I change that to: #include <boost/thread/detail/platform.hpp> this error goes away. However, there are a lot of places where headers are included using relative path, thereby causing compilation errors. Is there a workaround for this? Thanks, Raj -- Twitter: @Blismedia <http://twitter.com/#%21/blismobile> BlisMedia 32 Percy Street, London W1T 2DE www.blismedia.com <http://www.blismobile.com/> <http://www.blismobile.com/> [image: Follow on Twitter] <http://twitter.com/#%21/blismobile>[image: Blis Website] <http://www.blismobile.com/> This communication is from BlisMedia, which is a trading name of Breeze Tech (UK) Ltd, a company registered in England and Wales with registered number 06455773. Its registered office is 32 Percy Street, London W1T 2DE, United Kingdom. This communication contains information that is confidential and may also be privileged. It is for the exclusive use of the intended recipient(s). If you are not the intended recipient(s), please (1) notify info(a)blismedia.com<info(a)blismobile.com> by forwarding this email and delete all copies from your system and (2) note that disclosure, distribution, copying or use of this communication is strictly prohibited. Email communications cannot be guaranteed to be secure or free from error or viruses. All emails sent to or from a Blismobile email account are securely archived and stored by an external supplier. This email does not constitute a contractual agreement; such agreements are in specified contractual or Insertion Order (IO) form only and exclusively contain all the terms to which Breeze Tech )UK) Ltd will be bound. To the extent permitted by law, Breeze Tech (UK) Ltd does not accept any liability for use of or reliance on the contents of this email by any person save by the intended recipient(s) to the extent agreed in a contract or Insertion Order. Opinions, conclusions and other information in this email which have not been delivered by way of the business of Breeze Tech (UK) Ltd are neither given nor endorsed by it.

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Re: [Boost-users] asio - improving chat server example for my
by Marat Abrarov 21 May '12

21 May '12

Hi, John. > Many thanks for any help. I'm really enjoying Asio and other parts of Boost, but I still don't > understand the framework completely. Sorry, if I'm spamming you but feel free to read Asio examples at my project - http://sourceforge.net/projects/asio-samples. May be it can help in some architecture decisions. > 2- This might be way off, but I also wondered if I need to close all the sockets so that the thread group could join. Yes, you need to close all sockets (and other instances of asio::basic_io_object) having pending asynchronous operations (read/write for sockets, async_wait for timers, etc), related to the used instance of asio::io_service. Otherwise you can call asio::io_service::stop(). > I added 2 member functions to help me: > > void chat_server::close() > { > ? room_.close(); > } > > void chat_room::close() > { > ? std::for_each( participants_.begin(), participants_.end(), boost::bind(&chat_room::leave, this, _1) > ); > } > > I call this in my server app class's destructor before calling thread_group::join_all, but this has a > crash. The crash occurs right after chat_room::close() completes. I'm not confident in the way I used > bind(...), but I was able to see the function execute, and then the crash occurs later. You need to implement chat_participant::close() like it is done at: http://www.boost.org/doc/libs/1_49_0/doc/html/boost_asio/example/chat/chat_… Regards, Marat Abrarov.

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Deriving custom archive classes from boost::archive::text_oarchive_impl and boost::archive::text_iarchive_impl
by Aldo Longhi 21 May '12

21 May '12

*Note: Boost's archive scheme is based on symmetrical input and output archive classes. It's tedious to write about both of them all the time, so I'll use "?archive" to mean both "oarchive" and "iarchive".* *Summary:* After changing the base classes of my custom archives from binary_?archive_impl to text_?archive_impl, my custom archive classes are no longer "found" when the compiler is instantiating the serialize(...) methods in my other classes. *Background:* My application was successfully reading and writing files to disk using subclasses of binary_?archive_impl (the documentation and/or code comments recommend this over deriving from binary_oarchive). I needed to switch from a binary file format to a text format, so I switched the base classes of my custom archives to text_?archive_impl. That's when everything blew up. *The problem:* My custom archive classes add functionality, including some additional methods which do not exist in their Boost base classes; these methods are called in the serialize(...) methods in many of my classes, and they were working fine. After changing the base classes from binary_?archive_impl to text_?archive_impl, I received compilation errors all over the place complaining that my custom methods do not exist in text_?archive. Well, that's obvious (!!!), but they DO exist in my CUSTOM archives, and they were working JUST FINE when I was using Boost's binary base classes. What's the deal? *What I found, and my temporary - but undesirable - solution:* After tearing my hair out and going around in circles for about a day, this is what I found... 1) Some time ago (Boost 1.34 I believe), the files "binary_?archive.hpp" were split up into "binary_?archive_impl.hpp" and "binary_?archive.hpp" (the latter #include the former). This WAS NOT done to "text_?archive.hpp". (As a result, I changed my application's #include lines from "binary_?archive_impl.hpp" to simply "text_?archive.hpp".) 2) If I split up "text_?archive.hpp" into two parts and #include only the "..._impl.hpp" headers, everything works. (But I really DON'T want to modify my Boost installation!) 3) Looking more closely at these headers and fiddling around a bit, I found that if I use the original, unmodified headers and comment out the line BOOST_SERIALIZATION_REGISTER_ARCHIVE(boost::archive::text_oarchive) (and likewise for text_iarchive), then everything works fine again. (By the way I have similar lines in my own archive code to "register" my custom archives.) *The mystery, and my dilemma:* A) Why does the presence of those lines foul up the works? ...and why does removing them make things work? ...and what might I have broken (without knowing it) by doing so? B) Why were the "text_?archive.hpp" files NOT split up along with the "binary_?archive.hpp" files a long time ago? (Is the library broken? Should it be fixed?) C) Is there any way to solve this in my application code WITHOUT modifying my Boost installation? *P.S. I'm using Boost 1.48 and Visual Studio 2010 SP1 (64-bit)*

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Re: [Boost-users] Status of boost.lockfree
by Juan Ramírez 21 May '12

21 May '12

Why don't you try on boost-dev mailing list? Saludos! Juan On Mon, May 21, 2012 at 12:59 PM, Juan Ramírez <jramirez(a)inconcertcc.com> wrote: > Why don't you try on boost-dev mailing list? > > > Saludos! > Juan > > > > > On Sat, May 19, 2012 at 8:00 AM, niXman <i.nixman(a)gmail.com> wrote: >> >> There is someone alive? >> Or, I asked a very difficult question? >> >> Thanks! >> >> -- >> Regards, >> niXman >> _______________________________________________ >> Boost-users mailing list >> Boost-users(a)lists.boost.org >> http://lists.boost.org/mailman/listinfo.cgi/boost-users > >

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Compiler warns about 'reference to temporary' with iterator on shared memory map
by Rajalakshmi Iyer 21 May '12

21 May '12

Hello, Consider: typedef std::pair<int, int> value_type; typedef allocator<value_type, managed_shared_memory::segment_manager> ValueAllocator; typedef boost::interprocess::map<int, int, std::less<int>, ValueAllocator> A_map; class A { public: A() { /* Construct shared memory map */ } ~A() bool contains(int i); private: A_map* m_objA; }; inline bool A::contains(int i) { A_map::iterator itr = m_objA->find(i); return (itr != m_objA->end()); } Here, at the line A_map::iterator itr = m_objA->find(i); I see this warning: .../boost_1_49_0/include/boost/container/detail/tree.hpp:391:31: warning: returning reference to temporary [enabled by default] I dont see a reason for this. Can someone please point out if I am doing something wrong here? Thanks in advance, Regards, Raj -- Twitter: @Blismobile <http://twitter.com/#!/blismobile> BlisMobile Media 32 Percy Street, London W1T 2DE www.blismobile.com [image: BlisMobile] <http://www.blismobile.com/>[image: Follow on Twitter]<http://twitter.com/#!/blismobile>[image: Blis Website] <http://www.blismobile.com/> This communication is from BlisMobile Media, which is a trading name of Breeze Tech (UK) Ltd, a company registered in England and Wales with registered number 06455773. Its registered office is 32 Percy Street, London W1T 2DE, United Kingdom. This communication contains information that is confidential and may also be privileged. It is for the exclusive use of the intended recipient(s). If you are not the intended recipient(s), please (1) notify info(a)blismobile.com by forwarding this email and delete all copies from your system and (2) note that disclosure, distribution, copying or use of this communication is strictly prohibited. Email communications cannot be guaranteed to be secure or free from error or viruses. All emails sent to or from a Blismobile email account are securely archived and stored by an external supplier. This email does not constitute a contractual agreement; such agreements are in specified contractual or Insertion Order (IO) form only and exclusively contain all the terms to which Breeze Tech )UK) Ltd will be bound. To the extent permitted by law, Breeze Tech (UK) Ltd does not accept any liability for use of or reliance on the contents of this email by any person save by the intended recipient(s) to the extent agreed in a contract or Insertion Order. Opinions, conclusions and other information in this email which have not been delivered by way of the business of Breeze Tech (UK) Ltd are neither given nor endorsed by it.

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[asio] Correct handler signature for io_service::post/dispatch
by Gary Sanders 20 May '12

20 May '12

Currently I'm developing a server that uses Boost.Asio, version 1.49. It makes use of io_service::post and io_service::dispatch to invoke handlers running in the same process, but on different threads. Some of the handlers invoke a function with the following signature: void handler(std::string s); This works fine and no problems have been observed. However, subsequently I read in the asio documentation that the function signature of a handler invoked by post/dispatch *must* be in the following format: void handler(); Is my code working by chance or is the asio version 1.49 documentation out of date? Regards Gary Sanders

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boost asio http server vs indy httpserver component
by Christer Borgqvist 20 May '12

20 May '12

Hi, I have an application writen in Borland C++ Builder, using Indy HTTPServer component to handle each connection in blocking mode, each connection starts a new thread, if I want to do the same using boost what is the appropriate way to do that? appreciate any help. Christer

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[serialization][1.49]How to serialize shared_ptr<void>?
by harr999y 19 May '12

19 May '12

Hi,:) I'm doing saving the shared_ptr<void>,but it can't as "boost::serialization::tracking_level< T >::value != boost::serialization::track_never". And I know if it's shared_ptr<int>,I can use strong_typedef.But for the void,the strong_typedef cannot work. So can you give me some hint? Thanks, Harry -- View this message in context: http://boost.2283326.n4.nabble.com/serialization-1-49-How-to-serialize-shar… Sent from the Boost - Users mailing list archive at Nabble.com.

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Re: [Boost-users] Status of boost.lockfree
by niXman 19 May '12

19 May '12

There is someone alive? Or, I asked a very difficult question? Thanks! -- Regards, niXman

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asio - improving chat server example for my usage
by john grant 18 May '12

18 May '12

Hi,I could use some help to build on Asio's chat_server example so I can use it in my app. I want the server to have a main thread loop, like you would need if the server had a user interface or some other responsibility than just accepting client connections and echo-ing their input. I added a thread_group to call 'io_service::run' (to allow for asynchronous connections), letting the server have a main app loop for other responsibilities. I've learned enough about Asio by watching and reading Michael Caisse's excellent Asio presentation from BoostCon 2010 to feel somewhat comfortable using Asio and Threads together. I have a client app that connects well with the server app. ** I have a problem with my server app upon shutdown. The problem is that the thread_group I am using is stuck at the 'join_all' call (in the server app class's destructor). ** 1- I was worried that the threads were all dead, so I added a work object to my server app class, and now I delete it before I call 'join_all', but it still hangs here. 2- This might be way off, but I also wondered if I need to close all the sockets so that the thread group could join. I added 2 member functions to help me: void chat_server::close() { room_.close(); } void chat_room::close() { std::for_each( participants_.begin(), participants_.end(), boost::bind(&chat_room::leave, this, _1) ); } I call this in my server app class's destructor before calling thread_group::join_all, but this has a crash. The crash occurs right after chat_room::close() completes. I'm not confident in the way I used bind(...), but I was able to see the function execute, and then the crash occurs later. ** Do you know what I am doing wrong that causes the thread_group to hang? If I need to close the sockets, can you show me how to do that so I do not crash my app? ** For additional context, my server needs to send vehicle state to clients, among other messages. The server has a real time physics simulation. My client app will show a representation of the physics simulation. Many thanks for any help. I'm really enjoying Asio and other parts of Boost, but I still don't understand the framework completely. By the way, the IRC channel has been a big help already, but it seems everyone is busy in Aspen. :) John

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[filesystem] Memory leaks when building with MSVC 2010
by Christian Henning 18 May '12

18 May '12

Hi there, I'm stumbling over some memory leaks reported by MSVC when using boost::filesystem. Here is simple code sample that can reproduce the output below: #define _CRTDBG_MAP_ALLOC #include <stdlib.h> #include <crtdbg.h> #define BOOST_FILESYSTEM_VERSION 3 #include <boost/filesystem/convenience.hpp> namespace fs = boost::filesystem; int main(int argc, char* argv[]) { fs::path my_path( "C:\\bla.dat" ); _CrtDumpMemoryLeaks(); return 0; } -- Output: 'test.exe': Loaded 'C:\gil_contributions\solutions\vc10\test\x64\Debug\test.exe', Symbols loaded. 'test.exe': Loaded 'C:\Windows\System32\ntdll.dll', Cannot find or open the PDB file 'test.exe': Loaded 'C:\Windows\System32\kernel32.dll', Cannot find or open the PDB file 'test.exe': Loaded 'C:\Windows\System32\KernelBase.dll', Cannot find or open the PDB file 'test.exe': Loaded 'C:\Windows\System32\msvcr100d.dll', Symbols loaded. 'test.exe': Loaded 'C:\Windows\System32\msvcp100d.dll', Symbols loaded. Detected memory leaks! Dumping objects -> {268} normal block at 0x0000000000457450, 32 bytes long. Data: <C : \ b l a . d > 43 00 3A 00 5C 00 62 00 6C 00 61 00 2E 00 64 00 {145} normal block at 0x0000000000457F50, 24 bytes long. Data: < .? > A8 09 2E 3F 01 00 00 00 01 00 00 00 00 00 00 00 {143} normal block at 0x0000000000457E50, 16 bytes long. Data: <8 > 38 F9 16 00 00 00 00 00 00 00 00 00 00 00 00 00 {142} normal block at 0x0000000000457DD0, 16 bytes long. Data: <@ .? > 40 8B 2E 3F 01 00 00 00 00 00 00 00 00 00 00 00 {141} normal block at 0x0000000000457D50, 16 bytes long. Data: < .? > 10 8B 2E 3F 01 00 00 00 00 00 00 00 00 00 00 00 Object dump complete. The program '[1860] test.exe: Native' has exited with code 0 (0x0). Is this a known issue/nonissue? I have a test suite that uses boost::filesystem in numerous areas and the output is somewhat disturbing to me. Regards, Christian

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