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Tribool issue with logical operators && and ||
by Jean-Pierre Bergamin 14 May '08

14 May '08

Hello boost-users I just ran into quite a bad issue with boost::tribool. The overloaded operators && and || may (and normally do) evaluate the righthand side of logical expressions although not needed/permitted. They i.e. evaluate the rhs expression in a conjunction where the first term is false. This leads of course to very surprising results. IMHO, the provided operators should be removed or should honor normal semantics. Shall I issue a bug-report? I think the current situation is quite unconvincingly. Regards James

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[Boost.Foreach] error iterating custom wrappers
by johny5.coder＠gmail.com 13 May '08

13 May '08

Hello to everybody. Im using the great library Boost.Foreach and very happy with it, however currently I met some strange issue I want to show you. Im using custom wrappers to iterate over mapped values in std::map<> container. Here is the wrapper: template<typename CONT> struct Select2ndIt { CONT& cont; Select2ndIt(CONT& cont) : cont(cont) {} typedef typename CONT::mapped_type value_type; struct iterator : public std::iterator <typename CONT::iterator::iterator_category, value_type, typename CONT::iterator::distance_type> { typename CONT::iterator it; // typedef typename CONT::iterator::difference_type difference_type; typedef value_type* pointer; typedef value_type& reference; iterator(typename CONT::iterator it) : it(it) {} bool operator==(const iterator& other) const { return it == other.it; } bool operator!=(const iterator& other) const { return it != other.it; } iterator& operator++() { ++it; return *this; } iterator& operator++(int) { it++; return *this; } iterator& operator--() { --it; return *this; } iterator& operator--(int) { it--; return *this; } reference operator*() const { return it->second; } pointer operator->() const { return &it->second; } }; struct const_iterator : public std::iterator <typename CONT::const_iterator::iterator_category, value_type, typename CONT::const_iterator::distance_type> { typename CONT::const_iterator it; // typedef typename CONT::const_iterator::difference_type difference_type; typedef const value_type* pointer; typedef const value_type& reference; const_iterator(typename CONT::const_iterator it) : it(it) {} bool operator==(const const_iterator& other) const { return it == other.it; } bool operator!=(const const_iterator& other) const { return it != other.it; } const_iterator& operator++() { ++it; return *this; } const_iterator& operator++(int) { it++; return *this; } const_iterator& operator--() { --it; return *this; } const_iterator& operator--(int) { it--; return *this; } reference operator*() const { return it->second; } pointer operator->() const { return &it->second; } }; iterator begin() { return iterator(cont.begin()); } iterator end() { return iterator(cont.end()); } const_iterator begin() const { return const_iterator(cont.begin()); } const_iterator end() const { return const_iterator(cont.end()); } }; template<typename CONT> Select2ndIt<CONT> select2nd(CONT& cont) { return Select2ndIt<CONT>(cont); } And usage: std::map<int, unsigned> cont; BOOST_FOREACH(unsigned& value, alg::select2nd(cont)) value = 0; And MSVS 8.0 tells: error C2440: 'initializing' : cannot convert from 'const unsigned int' to 'unsigned int &' Without wrappers I can easily iterate as a non-const value: std::map<int, unsigned> cont; typedef std::pair<const int, unsigned> value_type; BOOST_FOREACH(value_type& value, cont) value.second = 0; works great. I guess my wrappers very close to STL iterators (they even inherit from std::iterator), however some unwanted constness is appearing, so I afraid it is some issue with Boost.Foreach library. I hope for some help or advice about this problem. Thanks. Evgeny.

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will be there a boost::library library?
by Yunior Peralta González 13 May '08

13 May '08

I wonder if boost have in mind to create a cross-platform library for loading libraries dynamically (at running time). I know that Qt has one (QLibrary), but the fact is that I don't like using Qt, I like programming with stl and boost. I just use Qt when I have to develop a visual application. Thanks in advance.

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[asio] async_write and callback order
by Ricardo Abreu 13 May '08

13 May '08

Hi all, I tried to clarify this on the irc but no one was sure about it: - when calling async_write multiple times, is there any guarantee that the handle_write callback I pass is called in the same order? For instance, I have the following code: #include "TCPConnection.h" #include <boost/bind.hpp> #include <iostream> using boost::system::error_code; using boost::bind; using namespace boost::asio; using namespace boost::asio::ip; namespace SockExperiment { //--------------------------------------------------------------------------------------- void TCPConnection::handleWrite(const error_code& error, size_t bytes_transferred) { std::string tmp = mBuffer.front(); // Copy the first element for printing mBuffer.pop(); // erase the first element std::cout << "writen msg \"" << tmp << "\".\n" << bytes_transferred << " bytes transferred." << std::endl; } //--------------------------------------------------------------------------------------- void TCPConnection::write(const std::string& msg) { /* Although the buffers object may be copied as necessary, ownership of the underlying memory blocks is retained by the caller, which must guarantee that they remain valid until the handler is called. */ mBuffer.push(msg); async_write(mSocket, buffer(mBuffer.back()), bind(&TCPConnection::handleWrite, shared_from_this(), placeholders::error, placeholders::bytes_transferred)); } } ... where mBuffer is an std::queue<std::string>, member of TCPConnection. Can I be sure that handleWrite will be called in the same order as write and, thus, that I will always pop the right element off of mBuffer? Otherwise, what is the proper way of ensuring that the memory I pass to asio::buffer remains valid? Thank you for the attention, Ricardo

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Booost.Signals reference to slot within combiner
by Yan Drugalya 13 May '08

13 May '08

I'm wondering, if it is possible to get reference to slot object within combiner. Something like this: struct Slot { Slot& operator()() { return *this; } }; struct Combiner { typedef const Slot& result_type; template<typename InputIterator> const Slot& operator()(InputIterator first, InputIterator last) { const Slot& slot = (*first); return slot; } }; … int main() { boost::signal< Slot (), Combiner > sig; Slot slot1; Slot slot2; sig.connect(slot1); sig.connect(slot2); const Slot& slot = sig(); // reference to slot1? ... } I'm not sure if last reference to slot can be safely used. What is the other ways how can I get reference to slot? Thanks in advance

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looking for boost::filesystem reference doc (some thing like javadoc api )
by Meir Yanovich 13 May '08

13 May '08

Hello all is there some where in the web boost::filesystem api reference document something like javadoc or http://www.cplusplus.com/reference/ something organized and comfortable (not like in the boost::filesystem site)

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serialization, many archives, cheap descrimination
by Victor Whiskey Yankee 12 May '08

12 May '08

Hello List, I have several classes, each put into it's own binary archive. How can I cheaply and efficiently determine the class type of a binary archive so that I know how to restore it? Thanks, Vic

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Need a web ui/interface to clear vertices from a boost graph
by Hardik Kheskani 12 May '08

12 May '08

Hi All- I am working on a c++ application that communicates with java components and builds a graph tree. Need to build a web interface (UI) of some sort to be able to remove vertices from the graph object within the c++ application. Can I have a php script that can somehow call a c/c++ function internally for this to get cleared? Any help/advice would be greatly appreciated. Hardik ____________________________________________________________________________________ Be a better friend, newshound, and know-it-all with Yahoo! Mobile. Try it now. http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ

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newbie question: unordered map missing?
by Julie Larson 12 May '08

12 May '08

Hello, I'm poking around in the library for something like a hashmap and I found this file: http://www.boost.org/doc/libs/1_35_0/boost/interprocess/indexes/unordered_m… (boost/interprocess/indexes/unordered_map_index.hpp) which includes this: #include <boost/unordered_map.hpp> which doesn't exist. Where can I find this file? Thank you -Julie

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s_directory(path) returns false in windows , path do exist
by Meir Yanovich 12 May '08

12 May '08

Hello all im new to boost::filesystem and im trying to run simple test on checking folder existence on windows 2k but even so the folder do excites im getting false from is_directory(path) what im doing wrong here ? #include "boost/filesystem.hpp" // includes all needed Boost.Filesystem declarations using namespace boost::filesystem; path path("I:\\ddd\\ccc\\",boost::filesystem::native); or path path("I:/ddd/ccc/"); or path path("I:\\ddd\\ccc\\"; if(is_directory(path)){ printf("is"); }else{ printf("none"); } what im doing wrong here?

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