half-band filter code

i m getting 3 errors in this program...i m not able to debug it...nyone cn help me


LIBRARY IEEE;
USE IEEE.std_logic_1164.all;
USE IEEE.numeric_std.ALL;
use IEEE.std_logic_arith.all;
use IEEE.STD_LOGIC_SIGNED.ALL;



entity half_band is
generic ( l: integer:= 13);
port(clk1, clk2:in bit:='0';
x: in signed (l-1 downto 0):=(others=>'0');
y: out signed (l-1 downto 0));
end half_band;

architecture hbf11 of half_band is
type data_bus is array (integer range <>) of signed (l-1 downto 0);
signal x_d: data_bus(0 to 10);
signal sum: data_bus(0 to 2);
signal sum_d: data_bus(0 to 3);

begin
shift: process (clk1,clk2)

begin
if (clk1='1' and clk1'event) then
for i in 1 to 10 loop
x_d(i) <= x_d(i-1);
end loop;
end if;
if (clk2='1' and clk2'event) then
sum_d(0)<=(sum(0) sra 7) + (sum(0) sra 8) + (sum(0) sra 11);
sum_d(1)<=(sum(1) sra 4);
sum_d(2)<=((sum(2) sra 2) + (sum(2) sra 5)) + ((sum(2) sra 6) + (sum(2) sra 8));
sum_d(3)<=(x_d(5) sra 1);
y <= (sum_d(0) - sum_d(1)) + ( sum_d(2) + sum_d(3)) ;
end if;
end process shift;
x_d(0)<=x;
add: for i in 0 to 2 generate
sum(i)<= x_d(2*i) + x_d(10 - 2*i);
end generate add;
end hbf11 ;