Creating a new Function

[Eric]

With XST I'm unable to create my own function called "Erics_Gate". If I
change the name to "and" or any other exsisting operator it works fine,
but I'd like this function to be called "Erics_Gate".

Any Ideas on how to define "Erics_Gate" as an operator?

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;
use IEEE.NUMERIC_STD.ALL;

entity mux is
Port ( A, B : in STD_LOGIC;
CLK : in STD_LOGIC;
Y : out STD_LOGIC);
end mux;

architecture Behavioral of mux is

function "Eric_gate" (L:std_ulogic; R:std_ulogic) return STD_ulogic is
begin
if L = '0' and R ='0' then return '1';
elsif L = '0' and R ='1' then return '1';
elsif L = '1' and R ='0' then return '0';
else return '1';
end if;
end;
begin

Process
begin
wait until clk = '1';
Y<= A Eric_gate B;

end process;
end Behavioral;