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noncopyable
by Hicham Mouline 05 Dec '08

05 Dec '08

AFAIU, deriving from boost::noncopyable disables _accidental_ object copying. Is it possible to implement a clone() const member function of the object to _explicitly_ get a copy of the object? Perhaps deriving boost::noncopyable makes it totally impossible to ever get a copy of an object without resorting to byte copy. Regards,

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shared_ptr to const object
by Jason Cipriani 05 Dec '08

05 Dec '08

How do I represent "const Object *" as a shared_ptr? Using "const shared_ptr<Object>" is not right, it makes the shared_ptr const, not the Object. Thanks, Jason

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scoped_ptr with destructor function
by Jason Cipriani 04 Dec '08

04 Dec '08

Does boost have something lightweight like a scoped_ptr but that lets you specify a custom delete function, or do I have to use a shared_ptr for that? Thanks, Jason

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Simple use case for boost exceptions
by Yang Zhang 04 Dec '08

04 Dec '08

With boost::exception, can I simply construct an exception with a custom what() message (without subclassing exception)? Thanks. -- Yang Zhang http://www.mit.edu/~y_z/

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[asio] sending multiple messages in the same soocket
by Henrique Aparício 04 Dec '08

04 Dec '08

Hi! I'm trying to implement an asynchronous client to communicate with a server using asio. To do this, I'm following the example of the http client ( http://tenermerx.com/Asio/asio-1.3.1/src/examples/http/client/async_client.… http://tenermerx.com/Asio/asio-1.3.1/src/examples/http/client/async_client.… ), but I'm trying to make it so that it can be used for a more general purpose. So in my implementation I have the same methods that appear in the example, but with only one method for reading the response. My main function calls the constructor of the client which is responsible for initializing variables and calling the chain of asynchronous methods. After this, the main function calls a method send(message), that puts the message I want to send in the variable request and runs the io_service. The problem is that I want to be able to call this send function several times, but it only works the first time I call it. For example: Client c(host, port); //remember that the constructor calls the asynchronous methods c.send("msg to send"); c.send("msg to send"); The message is actually sent the first time, but the rest of the times nothing happens. What am I missing? Can you help me? If you need more information to be able to help, please ask me. Henrique Aparício -- View this message in context: http://www.nabble.com/-asio--sending-multiple-messages-in-the-same-soocket-… Sent from the Boost - Users mailing list archive at Nabble.com.

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[multiindex] custom key extractor problem
by Stephan Menzel 04 Dec '08

04 Dec '08

Hi everyone, I could need a little advice using boost multiindex as follows: I have a Host class and I want to store HostPtrs in a multiindex container to a) have a member ip() as a key to unique hosts and b) be able to access random hosts via operator[]. The problem as I understand is the shared_ptr. Please consider this: class Host { public: Host(const boost::asio::ip::address &ip) : m_ip(ip) {}; const boost::asio::ip::address &ip(void) const throw () { return m_ip; }; private: Host(void) {}; boost::asio::ip::address m_ip; }; typedef boost::shared_ptr<Host> HostPtr; struct lthost { bool operator()(const HostPtr &h1, const HostPtr &h2) const { return (h1->ip() < h2->ip()); } }; struct giveip { // this is supposedly my key extractor typedef boost::asio::ip::address result_type; const result_type &operator()(const HostPtr &p) const { return p->ip(); }; }; typedef boost::multi_index_container< HostPtr, boost::multi_index::indexed_by< boost::multi_index::ordered_unique<giveip>, boost::multi_index::random_access<> > > HostSet; typedef HostSet::nth_index<0>::type HostSetOrderedIndex; typedef HostSet::nth_index<1>::type HostSetRandomIndex; Now inserting and accessing elements compiles fine, just when I try to erase something... int main(int argc, char **argv) { HostSet s; HostPtr p1(new Host(boost::asio::ip::address::from_string("127.0.0.1"))); HostPtr p2(new Host(boost::asio::ip::address::from_string("10.10.55.1"))); // now place a pointer to that host in the multiset. HostSetOrderedIndex &oi = s.get<0>(); oi.insert(p1); oi.insert(p2); oi.erase(p1); // booom } Basically, I want the index to access each ptr's ip() function to get the key rather than the ptr itself, which would be just random mem as far as I understand it. So the key extractor should work, shouldn't it? I also tried the lthost() function: typedef boost::multi_index_container< HostPtr, boost::multi_index::indexed_by< boost::multi_index::ordered_unique<boost::multi_index::identity<HostPtr>, lthost>, boost::multi_index::random_access<> > > But that doesn't work either. I guess it's accessing the HostPtr directly instead of dereferencing it. It does compile and also does the job but tests have shown that when I do this: HostSetOrderedIndex &oi = s.get<0>(); oi.insert(p2); HostSetRandomIndex &hsri = s.get<1>(); hsri.sort(); and then iterate over the container (hsri) the order will vary. Sometimes one of the hosts appears at [0] sometimes the other. I'm quite puzzled how this is supposed to work. Can you give me some hints?? Thanks a lot, Stephan PS: I know, the use case is kinda weird. Basically, I want to be able to insert elements with the set logic, and only the IP shall count as identity. Access via random access index is necessary to do hashing in a stable deterministic way over the container.

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Re: [Boost-users] [review][constrained_value] Review of Constrained Value Library begins today
by Robert Kawulak 04 Dec '08

04 Dec '08

Hi Jesse, From: "Jesse Perla" >4. If it is true in general, then this statement: >http://student.agh.edu.pl/~kawulak/constrained_value/constrained_value/ >rationale.html#constrained_value.rationale.no_floats >makes this library practically useless. This is the problem of limited usefulness of built-in floating point arithmetic rather than of this library. If you need constrained floats, use a library for reliable, repeatable floating-point computations. >typedef bounded<double> interest_rate; >interest_rate r1, r2; >change_bounds(r1, .8, .99); > >Now the interest rate bounds on r2 don't exist, right? This is a big >problem for me... It would mean that the bounds information is not kept on >the type, but on the instantiation... Sorry, but this makes no sense to me in the context of constrained values. If the current bounds are [0, 1] and you have r1 == .5 and r2 == .9, then what changing the bounds for the whole type to [.8, .99] would mean for r1? How the type is supposed to know that there is an instance that is not valid according to the new bounds? The type should keep handles to all its instances? Or the bounds should change anyway, leaving the instance in invalid state? So what would be the point of bounds checking, if you can't guarantee that once you assign a valid value then the object will remain valid? >6) Is there any way to get the library to compile: std::max(2, i) instead of >using i.value() as mentioned in the tutorial for a constrained i? No. These are just the rules for template functions. Implicit conversions are not taken into consideration in such case, so both the arguments have to be of identical type. >This >really is essential to make the library equivalent to normal operations, but >with extra type information. Again, I am willing to forgo ease of use on >the bounds checking for this... What I really want is the instantiation to >behave EXACTLY the same as an underlying type. So overloading the ++, +, >etc. are useful, but I would go further to say that perhaps everything could >be done by just going back to the underlying type... What you ask for is not possible in C++. You cannot have one type and use it exactly the same way as other type. I'll give you some examples (having constrained<string> cs): const char * s = cs.c_str(); // not possible Type constrained<string> can't have members that string has. char c = cs[0]; // not possible Type constrained<string> can't have operators that string has. How would you define such operator for constrained class template? How would you know what should be its return type in general case (without decltype available, of course)? Best regards, Robert

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another LNK2019 error
by Joseph A. Marks 04 Dec '08

04 Dec '08

error LNK2019: unresolved external symbol "class boost::unit_test::test_suite * __cdecl init_unit_test_suite(int,char * * const)" (?init_unit_test_suite@@YAPAVtest_suite@unit_test@boost@@HQAPAD@Z) referenced in function _main This is one of those "second order" calls where I cannot even readily find where the call is made to the above function. Is anyone else experiencing LNK2019 errors with Boost (esp. w.r.t. VS 2008) -- see below? Although I received one or two responses to the question posted below, in general, dealing with these linker errros is *MUCH* more difficult than dealing with compiler erros, and there is very little information to go on. Thanks in Advance! (-: Joseph > Subject: LNK2019 with boost::thread_group [!] > To: boost-users(a)lists.boost.org > Date: Monday, December 1, 2008, 11:59 AM > Here is what I'm trying to do: > > boost::thread_group threadGroup; > > for( ; port_min <= port_max; ++port_min ) > { > threadGroup.add_thread(new > boost::thread(boost::bind(CCUThread, port_min, strategy))); > } > > I am getting the following error: > > error LNK2001: unresolved external symbol "void > __cdecl boost::assertion_failed(char const *,char const > *,char const *,long)" > (?assertion_failed@boost@@YAXPBD00J@Z) > ..\bin\ccu_simulator.exe : fatal error LNK1120: 1 > unresolved externals > > Is this Boost-related? > > I found one posting that was somewhat similar on the web, > but the user found an error elsewhere, and it shed no light > on the situation. > > I am also getting several other LNK1120 errors that may be > related to Boost. > > I am converting working VS 6.0 (and occasionally 2005) code > to VS 2008; this has caused this link error to appear. > > I also have changed Boost from v. 1.31 to 1.36; whether > this affects the above linker errors I do not know. > > Any help would be appreciated. > > Last time I posted about a linking error, I received no > replies at all, so if someone knows something, please reply. > > Thanks Again! > > (-: > > Sincerely, > Joseph >

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recording member function calls with the calls' arguments
by Hicham Mouline 04 Dec '08

04 Dec '08

Hello, Is there any library that allows non-intrusively to record calls to member functions of existing classes as well as the arguments of the calls? It seems to be possible to do this with the decorator pattern. Regards,

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how to serialize a const class_name *object
by niranjan bangera 04 Dec '08

04 Dec '08

hi all, Am new to boost serialization concept. here i want to serialize these classes please help me to do this; i tried doing this but am gettin some compile time errors while serializing the object1, Please help me to do this, Boost version am using: 1_36_0 c++ compiler: GCC 4.1.1 (gnu-gcc-4.1.1-binutils-2.16.1/x86_64-pc-linux2.4/bin/gcc) Please help me to solve this simple concept.. Thanks in advance, Nina struct mystruct { const char * name; const char * name2; int number; } class my_class { private: const mustruct * object1 }

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