February 2005 - Boost-users

RE: [Boost-users] Custom containers
by Johnson, Donald W MVK Contractor 08 Feb '05

08 Feb '05

In your example size() returns 4 capacity() returns 6 end() returns a pointer to the 5th element When in doubt about standard container design examing std::vector is a good place to start. Good Luck -----Original Message----- From: Foster, Gareth [mailto:gareth.foster@siemens.com] Sent: Tuesday, February 08, 2005 8:36 AM To: 'boost-users(a)lists.boost.org' Subject: [Boost-users] Custom containers Hello all, If you were to write a container that had a certain size, say 6, but may not always contain 6 items, say it contains 4, what would it be best to have the following methods do? size() - returns 6 or 4? end() - returns an iterator on the 5th or 7th element? I'm not sure if the standard way of writing such things dictates a certain approach, or if it is purely down to the intended use. Thanks for any information. Gaz ******************************* * http://planetearthworm.com/ * *******************************

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boost::signals block/unblock
by frantz.maerten＠igeoss.com 08 Feb '05

08 Feb '05

Hi all, Maybe a stupid question: I wonder there's a way to connect a slot to signal (which gives a connection), temporarily disconnect this connection, and reconnect it later (like a block function) My problem is that I need to emit a signal to the connected slots given a condition. If a connection satisfies the precondition, it will be notified, otherwise it is temporarily disconnected. Thanks for any help

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msvc vc 6.0 SP6 internal heap limit reached
by Ira 08 Feb '05

08 Feb '05

All, I am a newbie who is trying out the serialization library. In that article, there is a demo program (demo.cpp) that i am trying to build. Along with several warnings ('dynamic_cast' used on polymorphic type...), the compiler is generating the following error: fatal error C1076: compiler limit : internal heap limit reached; use /Zm to specify a higher limit I have tried various values for /Zm (200 is recomended) and either i still receive this error, or if increase the value too much, the compiler generates the following error: fatal error C1204: compiler limit : internal structure overflow Since this seesaw response doesn't seem correct, i am wondering if there is a particular flag or combination thereof that would correct this problem? Thank you.

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Custom containers
by Foster, Gareth 08 Feb '05

08 Feb '05

Hello all, If you were to write a container that had a certain size, say 6, but may not always contain 6 items, say it contains 4, what would it be best to have the following methods do? size() - returns 6 or 4? end() - returns an iterator on the 5th or 7th element? I'm not sure if the standard way of writing such things dictates a certain approach, or if it is purely down to the intended use. Thanks for any information. Gaz ******************************* * http://planetearthworm.com/ * *******************************

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Boost libraries and no exceptions
by David Ward 08 Feb '05

08 Feb '05

Boosters: In our embedded environment, we compile everything with -fno-exceptions. I'm getting errors in the new program_options library because it has naked throw calls in it. I did see a definition of boost::throw_exception and changed the naked throw calls to use that. That seems to work. However, naked throw calls are littered throughout many of the libraries. Is there some generic way to get these libraries to compile with -fno-exceptions or do I have to go through and change all calls to throw to boost::throw_exception? Thanks, David Ward Acterna

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Bind question
by Surya Kiran Gullapalli 07 Feb '05

07 Feb '05

Hi all, This is a follow up to my previous message on boost::bind question. Please go thru the attached program. I've 2 structures X an Y, and i'm calling stable_sort on vectors of both the objects. But in one stable sort, i'm using the member variable directly, and in the other i'm using a member function to access that. When i use boost::bind with member variable directly, it has no problem (structure Y), But if i use member function to access the member variable, which is private, i'm getting compilation errors, The essence of the compilation error is given below.. ===================== ./boost/include/boost/lambda/detail/actions.hpp:86: error: no matching function for call to `boost::lambda::function_adaptor<int (X::*)()>::apply(int (X::*const&)(), const X&)' ./boost/include/boost/lambda/detail/function_adaptors.hpp:193: note: candidates are: static Result boost::lambda::function_adaptor<Result (Object::*)()>::apply(Result (Object::*)(), Object*) [with RET = int, Object = X, Result = int] ./boost/include/boost/lambda/detail/function_adaptors.hpp:197: note: static Result boost::lambda::function_adaptor<Result (Object::*)()>::apply(Result (Object::*)(), Object&) [with RET = int, Object = X, Result = int] ===================== what am i doing wrong. thanks in advance, Surya

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Bind question
by Surya Kiran Gullapalli 07 Feb '05

07 Feb '05

Hi all, I'm having this particular class class File { public: int get_size(); std::string get_name(); private: int size, std::string name; } ; and a vector of objects of this class. vector <File> files ; and if want to sort the elements of the container i use stable_sort (files.begin(), files.end()) // Invokes operator < if its defined. otherwise shows up an error. there's another form of stable_sort, in which we can call a sorting function of our own. Now my problem is the sorting criteria i use is dependent on runtime. say at times i want to sort by size and at other times i want to sort them by name of the file. The simple solution could be write 2 functions, sort_on_size and sort_on_filename which does the work. Now, the sorting order is also decided at runtime. So i write 2 more functions for that. The problem is the number of functions i use increase like any thing, which does not look good. The best way should be to use bind (or am i wrong here ?) from Boost library. But i'm not getting the syntax correctly here. the crude way could be stable_sort (files.begin(), files.end(), (bind (&File::get_size, _1) > bind (&File::get_size, _2))) ; that is call get_size() on first argument, and call get_size() on second argument, and compare those values, and return a boolean value. Can anybody please help me out with the syntax here. ?? Thanks in advance, Surya

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[signals] Painfully simple signals question
by Tony Juricic 07 Feb '05

07 Feb '05

Shame be where it belongs, after rading documentation, implementation, examples and test code, I am unable to write what should be simple signals code: --------------------------------------------- *.h typedef boost::function<void (void)> Callback; struct Signal { static void Connect(Callback f); }; ------------------------------------------------ *.cpp boost::signal<void (void)> mySignal; void Signal::Connect(Callback f) { // iterate over signal slots, if slot equals input f do nothing // otherwise connect f } Tony

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Signals and fuction documentation really old?
by Tony Juricic 07 Feb '05

07 Feb '05

..or am I having a day of profound stupidity. documentation: Boost.Function 3.5 Comparing Boost.Function objects me: okay, boost function object wrapper objects are comparable. documentation: Chapter 5 FAQ 5.1 Comparison between boost::function objects cannot be implemented well, and therefore will not be implemented. me:okay so it is not implemented documentation: 5.1 This essentially negates the usefulness of operator==in the context in which it is most desired:multitarget callbacks. me: great, multitarget callbacks is exactly why I am reading all this documentation documentation: 5.1 The Signals library has a way around this. me: great, if I only had an example of that way that wouldn't contain 2 free functions declared in the same file as the signal itself. Any help in clearing up my confusion greatly appreciated Tony

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deepcpy_ptr
by gast128 06 Feb '05

06 Feb '05

Dear all, I couldn't find functionality a la deep copy pointer in boost. Isn't this an idea to extend the smart_ptr library with it? Basically it has the same functionality as if the object was hold by value, but sometimes you want to dismiss the header file and only have a fwd decl: #include "bla.hpp" struct Foo { Bla m_Bla; }; deep copy: class Bla; //fwd decl. is sufficient { deepcpy_ptr<Bla> m_ptr; }; Or do I overlook something? Wkr, me

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