#include <boost/preprocessor/cat.hpp>
#include <boost/preprocessor/enum_params.hpp>

#define VER 1
// given alternative sets of macros:
#if VER==1
#define M0()
#define M1( arg0 )
#define M2( arg0, arg1 )
#define M3( arg0, arg1, arg2 )
#define M4( arg0, arg1, arg2, arg3 )
#elif VER==2
#define V0( x )
#define V1( x, arg0 )
#define V2( x, arg0, arg1 )
#define V3( x, arg0, arg1, arg2 )
#define V4( x, arg0, arg1, arg2, arg3 )
#endif

// I'm trying to write alternative versions of INVOKE for the above sets of macros,
// so that the interface below needs no #ifs
#if VER==1
#define INVOKE( n_args ) \
    BOOST_PP_CAT(M,n_args)( BOOST_PP_ENUM_PARAMS(n_args,arg) )
#elif VER==2
#define INVOKE( n_args ) \
    BOOST_PP_CAT(V,n_args)( dummy BOOST_PP_ENUM_TRAILING_PARAMS(n_args,arg) )
#endif

// the interface implemented in terms of INVOKE
#define A0() INVOKE(0)
#define A1( arg0 ) INVOKE(1)
#define A2( arg0, arg1 ) INVOKE(2)
#define A3( arg0, arg1, arg2 ) INVOKE(3)
#define A4( arg0, arg1, arg2, arg3 ) INVOKE(4)

int main()
{
	A2(1,2)
}