boolean bsearch(String s) {	// Returns true if and only if s equals one 
					//       of the Strings in v
		int    left, right;
		// If the String is anywhere, it is in positions left through right-1.
		// The String is not in a position before left.
		// The String is not in a position after right-1.
		left = 0;
		right = v.size();
		while  (left!=right-1)  {
			int  m  =  (right+left)/2;
			sm  =  (String)  v.elementAt(m);
			if  (sm.compareTo(s)<0)
				left  =  m;        // Move left to the middle.
			else  if  (sm.compareTo(s)>0)
				right  =  m;       // Move right to the middle.
			else  {
				left  =  m;
				right  =  m+1;
			}
		}
		return s.equals((String) v.elementAt(left));
	}