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[iostreams] Prepending and appending output data in a filter
by Edward Diener 29 Apr '08

29 Apr '08

I have a filter, derived from multichar_output_filter, in which I am both prepending data and appending data. In other words the data being written to the sink will be greater than the data being passed into the filter's 'template<typename Sink> std::streamsize write(Sink& dest, const char* s, std::streamsize n)' member function, which my filter is implementing. Is this an allowable use of filters ? Do I still return the 'n' streamsize data being passed in or do I return the actual length of the data being written ? Can I use the 'template<typename T> std::streamsize write( T& t, const typename char_type_of<T>::type* s, std::streamsize n );' function to write the data, or do I need to 'put' each character to the sink using the 'template<typename Sink> void put(Sink& snk, typename char_type_of<Sink>::type c);' function instead ?

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accumulator problem on visual studio 7.1
by Abir Basak 29 Apr '08

29 Apr '08

Hi, Is the boost accumulators library has too deep nesting in template declaration ? I am very interested to use it, but it increases the compile time drastically (with the inclusion of header #include <boost/accumulators/statistics.hpp> and sometimes it gives \boost\boost\lambda\detail\lambda_traits.hpp(53) : fatal error C1204: compiler limit : internal structure overflow, even for a simple program like computing mean of 3 numbers. So it seems there is a very deep template recursion which exceeds the compiler template substitution limit. Has anyone faced this kind of problem ? using the boost svn head version & MSVC 7.1 thanks abir -- Abir Basak, Member IEEE B. Tech , IIT KGP Software Engineer, Read Ink Technologies

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[serialization] serialization/utility.hpp missing include of xpressive/xpressive.hpp
by Sancho McCann 29 Apr '08

29 Apr '08

Anyone else agree this is a problem? I was trying to compile this simple program: #include <boost/numeric/ublas/vector_sparse.hpp> #include <boost/numeric/ublas/io.hpp> #include <iostream> int main(int argc, char** argv) { using namespace boost::numeric::ublas; mapped_vector<double> v(3,3); for ( unsigned i = 0; i < v.size(); ++i ) v(i) = i; std::cout << v << std::endl; return 0; } and the include hierarchy ends up including serialization/utility.hpp. This file uses the template mpl::and_, so I think it should include xpressive/xpressive.hpp. Sancho

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[interprocess] shared memory containing a vector of unions of strings/integers/doubles
by Jason Sachs 29 Apr '08

29 Apr '08

I'm trying to wrap my head around how I would implement a vector of unions of strings/integers/doubles in shared memory. (for those familiar with Micro$oft COM, this would essentially be a SAFEARRAY of VARIANTs) I got a quick example of shared memory working & seem to have a decent handle on the basics. I guess there are two things that I'm not quite confident in: (1) how to make a containable element work nicely within shared memory, e.g. if I have a structure S that needs to allocate shared memory dynamically during its lifetime (and automatically deallocate upon destruction), how do I store the allocator? (or do I?) If I allocate the memory myself and store it in an offset_ptr<>, I can do that, but I need it to manage the shared memory itself. In particular, one process may need to construct some anonymous object X within the shared memory segment and store the result in an offset_ptr<>, and another process may be the one destroying the memory of X later on. (2) unions or Boost.Variant that would work with shared memory-- gack! I am looking for insight both into the general case (all elements of the vector are polymorphic, vector size can vary) and the following specific case: I have a fixed-size vector, format "defined" at runtime using an array of enums that designate the type of variable that can be stored in each element of the vector. If it weren't for string support, I would just allocate a fixed-size chunk of memory rather than a vector, and do all the management within the chunk myself by calculating element size + offsets + what have you, which I've done before in other contexts. I can still do that if I can store a handle to the string (e.g. an offset into the shared memory segment?) rather than a pointer or other high-level object, so that my "vector" object becomes a class that just has to know how to allocate/deallocate memory on its own (hence question #1 still needs an answer, but I can avoid question #2). p.s. there seems to be a lot of missing methods in the documentation for shared_memory_object and managed_shared_memory (e.g. allocate(), construct(), destroy(), destroy_ptr()). Or am I missing something? http://www.boost.org/doc/libs/1_35_0/doc/html/boost/interprocess/shared_mem… http://www.boost.org/doc/libs/1_35_0/doc/html/boost/interprocess/basic_mana…

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any ETA for the BoostPro Binaries 1.35?
by Daniel Önnerby 29 Apr '08

29 Apr '08

Does anyone know if there are any plans for the boost consulting to release the BoostPro Binary Installer for Visual C++ for boost 1.35? I know I can build this myself, but it's always easier when someone else does it ;) Best regards Daniel

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Wrapping a nested c++ container to python
by RR 29 Apr '08

29 Apr '08

Hello I have some trouble with handling c++-container. I have these code: typedef struct foo { typedef std::vector<double> pt_coords; typedef std::vector<pt_coords> pt_list; }; foo return_foo(); Now I want to wrap these, but I don't know how! I have test this, but I think it's wrong: BOOST_PYTHON_MODULE(...) { implicitly_convertible<foo::pt_coords,tuple>(); implicitly_convertible<foo::pt_list,list>(); } By using this in Python I get: TypeError: No Python class registered for C++ class std::vector<std::vector<double, std::allocator<double> >, std::allocator<std::vector<double, std::allocator<double> > > > How to do this right? Greetings

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Re: [Boost-users] math
by Hicham Mouline 28 Apr '08

28 Apr '08

>Hicham Mouline wrote: >>> Are there libraries with class templates for the following concepts: >>> >>> . notion of mathematical function f(x1,x2,.,xn), and perhaps >>> derivation/integration >>> >>> . any-order multidim partial differential equations? >>> >>> . multidim stochastic differential equations? >Not at present, sorry, >Regards, John. If I were to attempt to implement such things, I would need to familiarize myself with boost::function maybe, boost::mpl, boost::math for special functions? I just finished reading the interesting "c++ template metaprogramming" which highlights such a large number of ideas that I will read once more. Assuming the general case of a set of stochastic processes x1....xm (X is a vector of xi): dx1 = a1(t, X) dt + b11(t,X) dW1 + b12(t,X)dW2 + .... + b1n(t,X) dWn ... dxm = am(t, X) dt + bm1(t,X) dW1 + bm2(t,X)dW2 + .... + bmn(t,X) dWn where ai: functionals of time and the state vector X bij: functionals of time and the state vector X Wj: non deterministic processes, governed by various statistical distributions (e.g. Normal) (perhaps ones listed in boost::math), with correlation matrix M n and m would have to be runtime variables in my case as the end-user might have thousands of processes. How would one model such a thing? class StochasticProcessesSet { template<class A, class B, class W> explicit StochasticProcessesSet(const std::vector<const A*>, const std::vector<const B*>, const std::vector<const W*>) { // 1. for correctness, runtime assertion that the sizes of the 3 vectors // are consistent with the system of equations above // 2. how to enforce that A and B are functionals that take the appropriate // number of arguments. // It seems impossible to mix a compile-time check on the template arguments // with the runtime variables n and m // 3. How to enforce W is one of the stat distributions } }; I would want to have special cases (perhaps for efficiency) for the above such as: 1 stochastic process dependent on n Wi with functionals dependent just on itself and time class StochasticProcess { .... }; What relationship should StochasticProcess have with StochasticProcessesSet? A final special case would be 1 process driven only by source of randomness, not n. Clearly, these first thoughts are not applicable, given than n and m need to be runtime. Regards,

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[general] General how-to-use-the-library documentation?
by Jason Sachs 28 Apr '08

28 Apr '08

Is there any other general (e.g. not specific to any of the particular libraries) about compiling/linking application programs that use Boost libraries? The only one I found was this: http://www.boost.org/doc/libs/1_35_0/more/getting_started/index.html I don't see the BOOST_ALL_DYN_LINK #define mentioned anywhere (e.g. to use shared libraries rather than static libraries, define this symbol in your makefile / IDE) other than the source files themselves, and am wondering what other usage parameters I need to know about. (p.s. the links to alternative format documentation on this page http://www.boost.org/doc/libs/1_35_0/doc/html/about.html are broken and yield 404 Not Found)

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Integer bounds checking with boost?
by Graham Reitz 28 Apr '08

28 Apr '08

I could have sworn I saw an example using boost to do simple numeric bounds checking. For example (silly): enum number_range {A=0,B=1,C=2,D=3,E=4,F=5,G=6,H=7}; class check_number_range { public: check_number_range(number_range a_number) { // Can this check be boostified? <--- Question located here. if ((a_number) > -1) && (a_number) < 8)) { // do something } else { throw out_of_range; } } }; thanks much, graham

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[numeric_conversion] rounding
by Peter 28 Apr '08

28 Apr '08

I'm wondering how to use the numeric_conversion library to perform rounding based on types. Assume I have a double value of 3.7. If I convert it to integer, the result should be 4. If I convert it to float, the result should be 3.7. The types I want to convert from and to are both specified in a template, i.e. they form an open set of types. >From reading the numeric_conversion docs I tend to think that the library can do what I want, but I'm unable to find out how. Can anybody help? Peter

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