problem in ldpc encoder c=G*c vhdl

Code VHDL - [expand]
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library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;
 
 
 
entity bn is
    Port ( u : in std_logic_vector(3 downto 0);
            clk:in std_logic;
              c : out std_logic_vector(7 downto 0));
end bn;
 
architecture Behavioral of bn is
 
 
type hmatrix is array (0 to 3 ) of std_logic_vector(7 downto 0);
constant G:hmatrix:=("10001100",
                              "01001001",
                      "00100011",
                      "00010110");
                        begin
                    
process(clk)
begin
if(clk'event and clk='1') then
 
 
 
 
c(7)<=(u(3) and G(31)) or (u(2) and G(23)) or (u(1) and G(15)) or (u(0) and G(7));
c(6)<=(u(3) and G(30)) or (u(2) and G(22)) or (u(1) and G(14)) or (u(0) and G(6));
c(5)<=(u(3) and G(29)) or (u(2) and G(21)) or (u(1) and G(13)) or (u(0) and G(5));
c(4)<=(u(3) and G(28)) or (u(2) and G(20)) or (u(1) and G(12)) or (u(0) and G(4));
c(3)<=(u(3) and G(27)) or (u(2) and G(19)) or (u(1) and G(11)) or (u(0) and G(3));
c(2)<=(u(3) and G(26)) or (u(2) and G(18)) or (u(1) and G(10)) or (u(0) and G(2));
c(1)<=(u(3) and G(25)) or (u(2) and G(17)) or (u(1) and  G(9)) or (u(0) and G(1));
c(0)<=((u(3) and G(24)) or (u(2) and G(16)) or (u(1) and  G(8)) or (u(0) and G(0)));
end if;
end process;
end Behavioral;