I have found IEEE.STD_LOGIC_ARITH to satisfy all my needs for arithmetical operations on STD_VECTORs, and IEEE.numeric_std, on contrary, only gives me trouble. But I always include both, never had problems with it...
---------- Post added at 23:18 ---------- Previous post was at 23:15 ----------
This is the set of libraries I always include to my modules:
use IEEE.STD_LOGIC_1164.ALL;
use ieee.std_logic_unsigned.all;
use ieee.std_logic_arith.all;
use IEEE.NUMERIC_STD.ALL;
I'm not sure how smart is it, though