E2（b）

Error_code copy_stack(Stack &dest,Stack &source)

{

Error_code detected=success;

Stack temp;

Stack_entry item;

while (detected==success&&!source.empty())

{

detected=source.top(item);

detected=source.pop();

if(detected==success) detected=temp.push(item);

}

while(detected==success&&!temp.empty())

{

detected=temp.pop(item);

detected=temp.pop());

if(detected==success)detected=source.push(item);

if(detected==success)detected=dest.push(item);

}

return detected;

}