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random numbers
by Anakreon 13 Sep '05

13 Sep '05

I am considering to use boost.random library but have a problem with efficiency. I have a class which provides two public methods: double exponential(double mean) and double getUniform(double min, double max) The implementation I have using boost.random is inefficient and I need some advice in order to improve it. In both the above methods I create a variate_generator object with a mersenne_twister generator and the appropriate distribution. The problem is that the methods are called often which leads to creation and destruction of the variate_generator and the distribution object. I can not store those objects as member variables because the parameters mean in exponential and (min, max) in getUniform varies Thanks in advanced Anakreon

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Re: [Boost-users] [BULK] Re: [BULK] [filesystem] function to determineavailable space
by Sohail Somani 12 Sep '05

12 Sep '05

> -----Original Message----- > From: boost-users-bounces(a)lists.boost.org > [mailto:boost-users-bounces@lists.boost.org] On Behalf Of Beman Dawes > Sent: Monday, September 12, 2005 2:20 PM > To: boost-users(a)lists.boost.org > Subject: [BULK] Re: [Boost-users] [BULK] [filesystem] > function to determineavailable space > Importance: Low > > "Sohail Somani" <s.somani(a)fincad.com> wrote in message > news:1C1EBEF8DBACDC439D038EA051674EC709C5D4@xbox.financialcad.com... > >> -----Original Message----- > >> From: boost-users-bounces(a)lists.boost.org > >> [mailto:boost-users-bounces@lists.boost.org] On Behalf Of > Beman Dawes > >> Sent: Monday, September 12, 2005 10:23 AM > >> To: boost-users(a)lists.boost.org > >> Subject: [BULK] [Boost-users] [filesystem] function to determine > >> available space > >> Importance: Low > >> > >> > >> I'm planning to add a filesystem function to determine > available disk > >> space. Perhaps something like: > >> > >> struct space_status > >> { > >> boost::uintmax_t available; // free space available to user > >> boost::uintmax_t total; // total space on volume > >> }; > >> > >> space_status filesystem_space( const path & p ); > >> > >> Comments? > > > > Standard unit of measure? Bytes? Megabytes? Gigabytes? > > Bytes. Individual bytes still matter in some applications. What about using a type that guarantees a certain amount instead of just "max" (which may vary)? Or equivalently, are we guaranteed that uintmax_t can hold, say one TB, on any platform that boost supports?

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Re: [Boost-users] [BULK] [filesystem] function to determine available space
by Sohail Somani 12 Sep '05

12 Sep '05

> -----Original Message----- > From: boost-users-bounces(a)lists.boost.org > [mailto:boost-users-bounces@lists.boost.org] On Behalf Of Beman Dawes > Sent: Monday, September 12, 2005 10:23 AM > To: boost-users(a)lists.boost.org > Subject: [BULK] [Boost-users] [filesystem] function to > determine available space > Importance: Low > > > I'm planning to add a filesystem function to determine > available disk space. > Perhaps something like: > > struct space_status > { > boost::uintmax_t available; // free space available to user > boost::uintmax_t total; // total space on volume > }; > > space_status filesystem_space( const path & p ); > > Comments? Standard unit of measure? Bytes? Megabytes? Gigabytes?

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[wave] Some bugs (posted here, 'coz SF bug-tracking is currently down)
by Mihalicza, Jozsef 12 Sep '05

12 Sep '05

Hello, I've built a spirit grammer to process the token sequence of wave. 1. Scope missing in macros. The first problem arose when I tried to write the wave token equivalent of chlit: struct token_lit : public boost::spirit::char_parser<token_lit> { token_lit(boost::wave::token_id id_) : id(id_) {} template <typename T> bool test(T id_) const { return BASE_TOKEN(id_) == BASE_TOKEN(id); } boost::wave::token_id id; }; The code above doesn't compile, because BASE_TOKEN uses constants from boost::wave without explicit scope. Lines to fix: token_ids.hpp(37-40,305,309). 2. Newline token reports bad position. For debug purposes I reported the match positions in the grammer actions using the file_position interface of the wave token type. The results were quite strange, sometimes pointing into the middle of a keyword, so I decided to take a smaller step and modified the wave example (the one in the documentation) just to see what happens, as follows: while (first != last) { std::cout << "value: \"" << (*first).get_value() << "\" pos: " << (*first).get_position ().get_file () << "(" << (*first).get_position ().get_line () << ") @" << (*first).get_position ().get_column () << std::endl; ++first; } Attached you can find some very small inputs and their corresponding outputs. 2.1. A file containing only whites and comments produced no tokens at all 2.2. Position of the enter token reports the new line number but the old column 2.3. The #line directive affects the position in a very strange way Please clarify if some of these are not errors. Oops, I almost forgot, I am using a fresh verison from the CVS repository already containing the fix for the SF bug #1274584. Best regards, József Mihalicza

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Re: [Boost-users] Some thoughts on Unary / BinaryFunctionConcept limitations
by Stephen Gross 12 Sep '05

12 Sep '05

> (1) The implementation of Unary and Binary (FunctionConcepts) > assume that > the return type is assignable ("r = f(arg)" tries to assign a value > to r). > But what if the return type is a reference? Won't the function > concept fail > to compile? Is this a bug? >That looks like a bug. >Here's a challenge for you: how would you fix this bug? In my own functor concept implementation, I used the function-pointer trick to make it work: ==== CODE ==== template<typename Func, typename Ret, typename Arg> struct special_UnaryFunctionConcept { void constraints() { Ret (Func::*x) (Arg) = Func::operator(); } }; ============== > (2) I'm implementing an NaryFunctionConcept for functors taking > more than 2 > arguments. The BOOST_CLASS_REQUIREx macro, however, appears to be > limited to > 4 types. This limits the NaryFunctionConcept to functors with up to > two > arguments. Is there a way to expand the BOOST_CLASS_REQUIREx macro > to handle > more than 4 types? >I'm sure there is a way. Can you think of a way to do it? Perhaps the >boost preprocessor library would help. Well, I was thinking that it BOOST_CLASS_REQUIREx for x > 4 could be added to the concept_check library in the same way that it is for x <= 4. Is this possible? > (3) I ran into a compiler problem when using BOOST_CLASS_REQUIREx; > when any > of the type macros have spaces or non-alphanumeric characters in > them, the > compiler reports an error. In the following example, I try to use > the macro > to require a UnaryFunctor taking a const std::string & and > returning an int. >Yes, you need to create a typedef for such types. This restriction >should be documented. I've checked in a fix to the docs. Ok, gotcha. Interesting... Thanks, --Steve

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Some thoughts on Unary / BinaryFunctionConcept limitations
by Stephen Gross 12 Sep '05

12 Sep '05

I'm just now learning about the concept_check library and how Unary and BinaryFunctionConcepts work in it. I have a few questions: (1) The implementation of Unary and Binary (FunctionConcepts) assume that the return type is assignable ("r = f(arg)" tries to assign a value to r). But what if the return type is a reference? Won't the function concept fail to compile? Is this a bug? (2) I'm implementing an NaryFunctionConcept for functors taking more than 2 arguments. The BOOST_CLASS_REQUIREx macro, however, appears to be limited to 4 types. This limits the NaryFunctionConcept to functors with up to two arguments. Is there a way to expand the BOOST_CLASS_REQUIREx macro to handle more than 4 types? (3) I ran into a compiler problem when using BOOST_CLASS_REQUIREx; when any of the type macros have spaces or non-alphanumeric characters in them, the compiler reports an error. In the following example, I try to use the macro to require a UnaryFunctor taking a const std::string & and returning an int. The code, however, fails to compile. Here's the code and error log: === CODE === template<typename T> class foo { BOOST_CLASS_REQUIRE3(T, int, const std::string &, boost, UnaryFunctionConcept); }; ============ Produces the following error (from g++): ==== ERROR LOG ==== test.cpp:42: error: parse error before `::' token test.cpp:42:80: pasting "&" and "UnaryFunctionConcept" does not give a valid preprocessing token test.cpp:42: error: parse error before `std' test.cpp:42:80: pasting "&" and "UnaryFunctionConcept" does not give a valid preprocessing token test.cpp:42:80: pasting "&" and "UnaryFunctionConcept" does not give a valid preprocessing token test.cpp:42: error: missing ';' before right brace test.cpp:42: confused by earlier errors, bailing out =================== Is this a bug? Thanks in advance for your thoughts, --Steve Stephen Gross Case Western School of Medicine Cleveland, OH "By Grabthar's hammer, by the sons of Worvan, you shall be avenged." - Dr. Lazarus

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Looking for example of BOOST_CLASS_REQUIREx
by Stephen Gross 12 Sep '05

12 Sep '05

I'm trying to find an example of how to invoke the BOOST_CLASS_REQUIREx macro (from the concept_check library). Can anyone point me in the right direction? Thanks, --Steve Stephen Gross Case Western School of Medicine Cleveland, OH "By Grabthar's hammer, by the sons of Worvan, you shall be avenged." - Dr. Lazarus

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Inheriting matrix_array
by Edward Grace 12 Sep '05

12 Sep '05

Dear all, I am evaluating aspects of the boost library. I wish to generate a simple implementation of ray transfer (ABCD) matricies, http://en.wikipedia.org/wiki/ABCD_matrix Since these matricies are 2x2 and will need multiplication, trace and other similar matrix like operations it makes sense to use: matrix_array<double,2> or boost::numeric::ublas::matrix_scalar<double> I wish to generate a ray transfer matrix class by overloading (say) matrix_array<double,2> and adding member functions such as: class rtm : boost::multi_array<double,2> { public: void setA(double val) { boost::multi_array<double,2>::operator()(0,0) = val; } }; Now, this is wrong... Essentially I just want to know something very simple.... When I inherit multi_array or any other class that I want to use the [] or (x,x) notation to access elements (subscript operators) how on earth do I do it? Your help will be greatly appreciated, this is driving me crazy! -ed

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scalar_matrix or containers and different contained types...
by Edward Grace 12 Sep '05

12 Sep '05

Dear All, Is there specifically a way I can do the following? boost::numeric::ublas::scalar_matrix<double> mD(3,3); boost::numeric::ublas::scalar_matrix<complex<double> > mC(3,3); mC = mD; Since I can do, complex<double> a; double b; a = b; without any problem why can the same thing be done with the container? Perhaps this is a more general point with C++ containers. If I can carry out a type conversion on the contained object (e.g. double -> complex<double> assuming the double is real) is there a way I can make sure the same carries through for casting of the contained objects? -ed -- Dr. Edward Grace Photonics Group, Physics Department Blackett Laboratory Imperial College SW7 2BW t: 020 759 47719 e: ej.grace(a)imperial.ac.uk w: http://ptweb.op.ph.ic.ac.uk/~graceej

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Serialization of template classes via base
by Bruno Martínez 12 Sep '05

12 Sep '05

Hi. This has been asked before here http://lists.boost.org/boost-users/2005/05/11706.php but I didn't understand the workaround. What I want is to serialize class B where class A { ... }; template<...> class B : public A { ... }; when I have an A*. The workarounds proposed were using RTTI non portably, or registering the classes each time. How would such solution look like? Regards, Bruno

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