library ieee;
use ieee.std_logic_1164.all;
entity if01 is
port (a : std_logic;
b : std_logic;
sel : std_logic_vector (1 downto 0);
s : out std_logic);
end if01;
architecture behav of if01 is
begin
s <= a when sel = "01"
else b when sel = "10";
end behav;