title: how can I use an infix expression in a case statement in VHDL?
body: <p>I want to compare two binary logic vectors A, and B. However my code won't compile and I am not sure why I am not allowed to use comparison statements here. can anyone help me? My problem is that I am new to VHDL  and I need some tips</p>
  
  <pre><code>library IEEE;
  use IEEE.STD_LOGIC_1164.ALL;
  
  --entity declaration of IC74x85 with port definitions
  entity IC74x85 is
  port(    A : in std_logic_vector(3 downto 0);  --input A is a 4 bit binary number
       B : in std_logic_vector(3 downto 0);  --input B is a 4 bit binary number
       ALTBOUT : out std_logic;   -- A &lt; B
       AEQBOUT : out std_logic;   -- A = B
       AGTBOUT : out std_logic    -- A &gt; B
  );
  end IC74x85;
  
  --architecture of entity
  architecture IC74x85_arch of IC74x85 is
  
  begin
  process(A,B)
  begin
      case A is
       when (A &lt; B) =&gt; ALTBOUT &lt;= '1';
       when (A &gt; B) =&gt; AGTBOUT &lt;= '1';
       when (A = B) =&gt; AEQBOUT &lt;= '1';
       when others =&gt; ALTBOUT, AGTBOUT, AEQBOUT &lt;= '0';
       end case;
  end process;
  end IC74x85_arch;
  </code></pre>
  
  <p>** Error: C:/Users/Steve/Desktop/Ass1/case signal assignment.vhd(21): Type error resolving infix expression "&lt;" as type ieee.std_logic_1164.STD_LOGIC_VECTOR.</p>
  
  <p>** Error: C:/Users/Steve/Desktop/Ass1/case signal assignment.vhd(21): Choice in CASE statement alternative must be locally static.</p>
  
  <p>** Error: C:/Users/Steve/Desktop/Ass1/case signal assignment.vhd(22): Type error resolving infix expression ">" as type ieee.std_logic_1164.STD_LOGIC_VECTOR.</p>
  
  <p>** Error: C:/Users/Steve/Desktop/Ass1/case signal assignment.vhd(22): Choice in CASE statement alternative must be locally static.</p>
  
  <p>** Error: C:/Users/Steve/Desktop/Ass1/case signal assignment.vhd(23): Type error resolving infix expression "=" as type ieee.std_logic_1164.STD_LOGIC_VECTOR.</p>
  
  <p>** Error: C:/Users/Steve/Desktop/Ass1/case signal assignment.vhd(23): Choice in CASE statement alternative must be locally static.</p>
  
  <p>** Error: C:/Users/Steve/Desktop/Ass1/case signal assignment.vhd(24): near ",": expecting &lt;= or :=</p>