macro define@struct name,[field,type,def]
 ......
    macro name value \\{
   forward
     match , value \\\{ type def \\\}
     match any, value \\\{ \\\local ..field
                           ;..field: type value                       ;was
                           ..field = $                                ;now
                           type value
                           ; original code follows
                           if ~ field eq .
                            rb sizeof.#name#field - ($-..field)
                           end if \\\}
   common \\} \} }
    

struct a
 x db ?
 y db ?
ends

var=0
var=var+3  ;var is NOT a constant

repeat var
 a %,%+1
end repeat