procedure lrot( var t : tree );
	var	temp : tree;
		a : integer;
	begin
		temp := t;
		t := t^.right;
		temp^.right := t^.left;
		t^.left := temp;
		{*** adjust balance ***}
		a := temp^.bal;
		temp^.bal := a - 1 - max( t^.bal, 0 );
		t^.bal := min( a-2, a+t^.bal-2, t^.bal-1);
	end;