phone_number ::= "(" area_code ")" prefix "-" suffix; area_code ::= number number number; prefix ::= number number number; suffix ::= number number number number;
auto area_code = axe::r_numstr(3); auto prefix = axe::r_numstr(3); auto suffix = axe::r_numstr(4); auto phone_number = '(' & area_code & ')' & prefix & '-' & suffix;