#define EXPR(unused, x, data) \

    case x: my_func(BOOST_PP_TUPLE_ELEM(2, 0, data) , offsetof(my_struct, arr[x].BOOST_PP_TUPLE_ELEM(2, 1, data)))); break;

     

    #define MY_MACRO(x, arg, my_field) \

    switch(i)\

    {\

    BOOST_PP_REPEAT(x, EXPR, (arg, my_field))\

    }