Re: [Boost-users] Template instantiation function arguments and Boost.Preprocessor

hi,

i have a template function, the arguments of which i wish to have depend on a non-type int template argument:

template<int n> double f<n>( double arg0, double arg1, ..., double argn ) // ... is not

Hi, thanks for your answers, Because I had tested just with : 1. static double sum(double d1, double d2, double d3) { return d1+d2+d3; } vs 2. static double sum(double d[3]) { return d[0]+d[1]+d[2]; } with calls to sum() in a tight loop. I suspect boost::array is equivalent to 2. was some 40% faster than 2 with advanced intel optimization. Could you elaborate on the recursive generation? Rds, template struct Tree { typedef boost::array parameters_types; }; From: boost-users-bounces@lists.boost.org [mailto:boost-users-bounces@lists.boost.org] On Behalf Of Ovanes Markarian Sent: 28 January 2008 21:27 To: boost-users@lists.boost.org Subject: Re: [Boost-users] Template instantiation function arguments and Boost.Preprocessor Hi, besides the more complex possibility to use boost::tuple and generate recursive Tree<X> List : derived from Tree<X-1> ...: derived from Tree<0> specialization, why not using a boost::array instead? Here an example: template struct Tree { typedef boost::array parameters_types; T sum(parameters_type const& p) { return std::accumulate(p.begin(), p.end(), 0); } }; This is type safe and fast ;) and your users can initialize boost array with an initializer list like: parameters_type x = { 1, 2, 3, 4, 5... }; Regards, Ovanes On Jan 28, 2008 8:26 PM, Hicham Mouline wrote: After some though, here is more precisely what I'd like to have... I apologize that it is quite different from the initial problem: template<int n> class Tree { static double sum(); // }; If the user instantiates tree<2>, he should get: template<> class Tree<2> { static double sum(double d1, double d2); }; template<> class Tree<3> { static double sum(double d1, double d2, double d3); }; etc etc... so that in user code, for e.g.: double d= Tree<4>::sum(d1, d2, d3, d4); should compile. Is it possible for me to just define the template Tree for the n-case without the 2- and 3- specializations? Rds, -----Original Message----- From: boost-users-bounces@lists.boost.org [mailto:boost-users-bounces@lists.boost.org] On Behalf Of Steven Watanabe Sent: 28 January 2008 16:42 To: boost-users@lists.boost.org Subject: Re: [Boost-users] Template instantiation function arguments and Boost.Preprocessor AMDG Hicham Mouline wrote: the variadic notation for var number of args

{ // for(int i=0; i

int main() { return x = f<3>( 1.0, 2.0, 3.0 ); }

BOOST_PP_REPEAT can't seem to do the job as the template argument n needs to be known at the preprocessing stage, which happens before the template instantiation stage ( this is part of compilation)

I don't understand why you want n to be passed explicitly. Can't it be deduced from the number of arguments (warning untested): #define SUM_IMPL(z, n, data) + arg ## n #define F_DEF(z, n, data) double f(BOOST_PP_ENUM_PARAMS_Z(z, n, double arg)) { return(0.0 BOOST_PP_REPEAT_ ## z(n, SUM_IMPL, ~)); } BOOST_PP_REPEAT(MAX_ARITY, F_DEF, ~) In Christ, Steven Watanabe _______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.516 / Virus Database: 269.19.14/1247 - Release Date: 1/28/2008 10:59 AM _______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users