July 2010 - Boost-users - lists.boost.org

boost_python: static vs shared library sizes on Windows
by David Aldrich 28 Jul '10

28 Jul '10

Hi I asked for help a week or so back regarding storing boost_python as a vendor library in our project's svn repository. The aim being to relieve our Windows developers of the effort of installing and building boost. This also ensures that everyone is using the same version. I have built shared libraries for boost_python and everything works nicely now except that it is necessary to include the path to the boost libraries in the system's PATH variable. I would rather not have to modify PATH, so I considered using static libraries instead. However, I was surprised to find that the static libraries are very much bigger than the shared libraries. So I would rather use shared libraries. Is there a way of telling the .exe file the path to the necessary dll's at build time? Is this a purpose of a manifest file? Best regards David

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Is there rotate-shifts in Boost?
by Murilo Adriano Vasconcelos 28 Jul '10

28 Jul '10

Hi, I am a GSoC student and I am implementing a library to handle integral values. I want to know if exists functions to do integer rotate shifts in Boost. If it not exists I am suggesting these functions: http://svn.boost.org/svn/boost/sandbox/SOC/2010/bits_and_ints/boost/integer… To do right and left rotation shifts. And want to know if is better to check if the length of rotation is less than the size in bits of the type. Best, -- Murilo Adriano Vasconcelos http://murilo.wordpress.com

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[Iterator][enable_if] Why use additional type for the enabler?
by Robert Jones 28 Jul '10

28 Jul '10

The iterator facade documention suggests that controlled conversion of iterators between const and mutable variants can be achieved by application of enable_if. Why does this need to involve an additional 'enabler' type, rather than exploiting the default void type of the enable_if template? Thx, - Rob.

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[Serialization] #include order
by dariomt＠gmail.com 28 Jul '10

28 Jul '10

Hi all, Compiling the following program with Boost 1.42 fires an static assertion in boost/serialization/shared_ptr.hpp:153. This is expected. But if I change the order of includes (compile with -DCHANGE) the assertion fires in boost/serialization/shared_ptr.hpp:121. The assertion is expected but I found it strange that I end up compiling a different part of the same file... The code in that section seems related to serialization of shared_ptr in version 1_32, but since I'm not able to understand the difference, I'm just reporting it in case the order of #includes might affect how shared_ptr's get serialized. Regards ---code--- #include <boost/shared_ptr.hpp> #ifndef CHANGE #include <boost/serialization/shared_ptr.hpp> #endif #include <boost/archive/xml_oarchive.hpp> #include <boost/archive/xml_iarchive.hpp> #ifdef CHANGE #include <boost/serialization/shared_ptr.hpp> #endif void test() { boost::shared_ptr<int> p (new int); *p = 12345; boost::archive::xml_iarchive ia(std::cin); boost::serialization::load(ia, p, 0); }

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[boost.filesystem v3] recursive_directory_iterator throws unexpectedly
by Tan, Tom (Shanghai) 28 Jul '10

28 Jul '10

In boost::filesystem v3, while it's possible to choose a no-throw version of recursive_directory_iterator by passing an boost::system::error_code object to its constructor, like this: boost::system::error_code m_ec; for ( recursive_directory_iterator itr(root, m_ec), end_itr; itr != end_itr; ++itr) However, because in the implementation of the recursive_directory_iterator::increment(), directory_iterator is always constructed with the throw version, it would cause exception throws during the for-loop while accessing folders like \System Volume Information on Windows: void increment() { BOOST_ASSERT(m_imp.get() && "increment of end recursive_directory_iterator"); m_imp->increment(0); if (m_imp->m_stack.empty()) m_imp.reset(); // done, so make end iterator } Where m_imp is an object of recur_dir_itr_imp: void recur_dir_itr_imp::increment(system::error_code* ec) // ec == 0 means throw on error { ... } As it's not possible to catch this exception within the for-loop and continue the loop, it greatly limits the use of recursive_directory_iterator. With rough check, V2 does not seem to have this problem. Is this a bug or change on purpose? I personally would expect the directory_iterator to behave the same as recursive_directory_iterator in this case. Regards, Tom

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program_options, multiple [sections] from a config file
by rrlangly 28 Jul '10

28 Jul '10

I'm using boost program_options 1.41 and would like to know if anyone has a better idea than what I'm trying to do. I am reading from a config file some basic parameters per section, but I have multiple sections. The problem is there could be any number of [sections] in this file, so I don't know what it is ahead of time. [server] name="a" ip="1.2.3.4" [server_2] name="b" ip="4.5.6.7" [server_3] name="c" ip="8.9.0.1" Thanks, -- View this message in context: http://old.nabble.com/program_options%2C-multiple--sections--from-a-config-… Sent from the Boost - Users mailing list archive at Nabble.com.

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[serialization] transparently treating a class like a built-in type
by Kenneth Riddile 28 Jul '10

28 Jul '10

I have some xml archives that store a lot of floating point values. I would like to read these into a program that is designed to easily switch between using floats and a custom fixed-point type via a typedef. The way that would be easiest would be to add a serialize() method to the fixed-point class definition. However, the xml archive requires that I use an nvp wrapper. Since the data was originally serialized out as plain floats, the data looks something like this: <x>0.95260203</x> <y>0.87517798</y> <z>0.54323343</z> whereas, to serialize this into my fixed-point type, it would need another level of indirection due to the additional required nvp wrapper like so: <x><value>0.95260203</value></x> <y><value>0.87517798</value></y> <z><value>0.54323343</value></z> Is there a way to accomplish what I'm trying to do? The fixed-point type is convertible from (but not to) a float if that helps.

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assigning a value to a matrix shared_ptr
by Max S. Kaznady 28 Jul '10

28 Jul '10

Hello, I am trying to assign a value to the matrix, which is pointed to by the shared pointer, but I am not sure which operator to call, please have a look at the following code, I commented the problem: #include <boost/numeric/ublas/matrix.hpp> #include <boost/numeric/ublas/io.hpp> int main () { using namespace boost::numeric::ublas; matrix<double> m (3, 3); boost::shared_ptr<matrix<double>> m2(new matrix<double>(3,3)); for (unsigned i = 0; i < m.size1 (); ++ i) for (unsigned j = 0; j < m.size2 (); ++ j) { m (i, j) = 3 * i + j; /// now do the same operation to the shared pointer's matrix m2->operator*(i, j) = 3 * i + j; // this results in a runtime error } std::cout << m << std::endl; // And how do we print m2 ? } Thanks, Max

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Using boost::thread to keep all cores busy
by Internet Retard 27 Jul '10

27 Jul '10

I have a new 2 core CPU and I've been experimenting with boost::threads by attempting to keep both cores busy independent of each other. Say I have a queue of 4 tasks to do. Each task will be handled by one thread. Some tasks will take longer to complete than others so I can't use thread_group with 2 threads at a time and join_all() as one core may finish before the other and set idle until the second thread completes. I use boost::thread::hardware_concurrency() to determine how many CPU cores I have available. My problem is *knowing* when a thread/CPU core finishes a task and is available for another task. Here is some sample code. I commented what I think would be an approach. Any suggestions or hints? std::queue<std::string> string_queue() { std::queue<std::string> sq; sq.push("AAA"); sq.push("BBB"); sq.push("CCC"); sq.push("DDD"); return sq; } void worker(std::string& S) { std::cout << S << std::endl; } int main() { std::cout << "Number of Cores: " << boost::thread::hardware_concurrency() << std::endl; std::queue<std::string> strings = string_queue(); while ( !strings.empty() ) { // if ( a CPU core is available ) // { boost::thread t(boost::bind(&worker, strings.front())); t.join(); strings.pop(); // } // else // { // wait awhile and check if a CPU core is available again. // } } return 0; } _________________________________________________________________ Hotmail: Trusted email with Microsoft’s powerful SPAM protection. https://signup.live.com/signup.aspx?id=60969

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subcommands with program_options (like svn command)
by Adrien Guillon 27 Jul '10

27 Jul '10

Hello all, I am writing a moderately complex command-line application, and I have been looking at program_options for simplifying my life. The best way to describe what I want to do, is in term of the svn command (which I assume most people are familiar with). In particular, what I want to do is expose a number of subcommands for controlling the application, each of which has their own particular options. For example, if I were to write svn using program_options, then the first command I have to accept could be one of: add, checkout, del, log, etc. Each of these commands has a separate list of arguments that they accept themselves. I'm a bit stumped on how exactly to do this with program_options, because the first argument (which I can do using positional arguments) decides what other arguments are valid. Any thoughts or suggestions? Thanks! AJ

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