VHDL code for Sequence Detector

Sequence -1011 
--Behavioral code of Mealy FSM for 1011 sequence detector

library IEEE;

use IEEE.STD_LOGIC_1164.ALL;

entity sd1011 is
    Port ( x,clk : in  std_logic;
           z : out  std_logic);
end sd1011;

architecture Behavioral of sd1011 is
signal state,nextstate:integer range 0 to 3;

begin
process(state,x)
begin
case state is
when 0 => if x='0' then nextstate<=0;z<='0';
 else nextstate<=1;z<='0'; end if;

when 1 => if x='0' then nextstate<=2;z<='0';
else nextstate<=1;z<='0';end if;

when 2 => if x='0' then nextstate<=0;z<='0';
else nextstate<=3;z<='0';end if;

when 3 => if x='0' then nextstate<=2;z<='0';
else nextstate<=1;z<='1';end if;

when others=> null;
end case; end process;

process(clk)
begin
if (rising_edge(clk)) then
state<=nextstate;
end if;
end process;

end Behavioral;

---- Second way to write same Mealy FSM behavioral model
library IEEE;

use IEEE.STD_LOGIC_1164.ALL;

entity sdz1011 is
    Port ( x,clk : in  std_logic;
           z : out  std_logic);
end sdz1011;

architecture Behavioral of sdz1011 is
signal state:integer range 0 to 3;

begin
process(clk)
begin

if (rising_edge(clk)) then

case state is
when 0 => if x='0' then state<=0;else state<=1; end if;

when 1 => if x='0' then state<=2;else state<=1; end if;

when 2 => if x='0' then state<=0;else state<=3; end if;

when 3 => if x='0' then state<=2;else state<=1; end if;
when others=> null;
end case;
if (state=3 and x='1') then z<='1'; else z<='0'; end if;
end if;
end process;

end Behavioral;

VHDL code for Sequence/Pattern Detector (0110)
---Dataflow model for the sequence 0110
---equations are from Mealy FSM + guidelines to reduce amount of logic(refer roth book)

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;

entity sdd0110 is
Port ( x,clk : in  std_logic;
           z : out  std_logic);
end sdd0110;

architecture Behavioral of sdd0110 is
signal a,b:std_logic;
begin
process(clk)
begin
if rising_edge(clk) then
a<= x and not b;
b<= x and ( a or b);
end if;
end process;
z<= not x and a and b;
end Behavioral;