Erase all members of a class

class a_class
{
public:
    a_class() {...}
    int some_method(int some_param) {...}

    int value_1;
    int value_2;
    float value_3;
    std::vector<some_other_class*> even_more_values;
    /* and so on */
 }

 a_class a_instances[10];

 void some_function()
 {
     do_stuff();
     do_more_stuff();

     memset(a_instances, 0, 10 * sizeof(a_class)); // <===== WTF?
 }

...
for(size_t i=0; i < 10; i++)
    objects[i].clear();

void clear() {
    a_object o;
    o.swap(*this);
}

void clear()
  {
  value1=0;
  value2=0;
  value_3=0f;
  even_more_values.clear();
  }

class a_class
{
public:
    a_class() {...}
    ~a_class() { /* make sure that even_more_values gets cleaned up properly */ }

    int some_method(int some_param) {...}

    int value_1;
    int value_2;
    float value_3;
    std::vector<some_other_class*> even_more_values;
    /* and so on */
 }

 void some_function()
 {
     std::vector<a_class> a_instances( 10 );

     // Pass a_instances into these functions by reference rather than by using
     // a global. This is re-entrant and more likely to be thread-safe.
     do_stuff( a_instances );
     do_more_stuff( a_instances );

     // a_instances will be cleaned up automatically here. This also allows you some
     // weak exception safety.
 }