entity COMPARE is 
  port (A : in bit_vector (3 downto 0);
        B : in bit_vector (3 downto 0);
        LT, EQ, GT : out bit);
end entity COMPARE;
     
architecture BEHAV2 of COMPARE is
begin
  process (A, B)
  begin
    LT <= '0';
    GT <= '0';
    EQ <= '0';
    if (A = B) then
      EQ <= '1';
    elsif (A < B) then
      LT <= '1';
    else
      GT <= '1';
    end if;
  end process;
end BEHAV2;
           
architecture BEHAV3 of COMPARE is
begin
    GT <= '1' when A > B else '0';
    LT <= '1' when A < B else '0';
    EQ <= '0' when A = B else '0';
end BEHAV3;