Re: [Boost-users] Variable-length template argument lists in C++03?

From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2008-07-10 12:48:53

AMDG

Robert Dailey wrote:
> Hi,
>
> Is there a way that I can provide variable length template argument 
> lists in C++03 using boost? An example of what I want to achieve is below:
>
> template< typename t1, typename t2, ..., typename tN >
> void MyFunction( t1 param1, t2 param2, ..., tN paramN )
> {
>     boost::tuple<t1, t2, ..., tN> myTuple;
>     AnotherFunction( param1, param2, ..., paramN );
> }
>
> Right now to do this I have to create several class specializations 
> which gets very nasty. Help is appreciated. Thanks.

The easiest way to do it is using the preprocessor:

// scratch.cpp
#ifndef BOOST_PP_IS_ITERATING

#include <boost/preprocessor/iteration/iterate.hpp>
#include <boost/preprocessor/repetition/enum_params.hpp>
#include <boost/preprocessor/repetition/enum_binary_params.hpp>
#include <boost/tuple/tuple.hpp>

#define BOOST_PP_FILENAME_1 "scratch.cpp"
#define BOOST_PP_ITERATION_LIMITS (1, 5)

#include BOOST_PP_ITERATE()

#else

template<BOOST_PP_ENUM_PARAMS(BOOST_PP_ITERATION(), class T)>
void MyFunction(BOOST_PP_ENUM_BINARY_PARAMS(BOOST_PP_ITERATION(), const 
T, &t)) {
    boost::tuple<BOOST_PP_ENUM_PARAMS(BOOST_PP_ITERATION(), T)> myTuple;
    AnotherFunction(BOOST_PP_ENUM_PARAMS(BOOST_PP_ITERATION(), t));
}

#endif

In Christ,
Steven Watanabe