title: VHDL found '0' definition of operator "+" cannot determine exact overloaded matching definition for "+"
body: <p>I have the problem that this line <code>B1 &lt;= (-c1 * (A3 + A1) + A3 + A2 - A1);</code> keeps showing up as an error. I am aware that this problem already exists on stackoverflow, but none of the solutions have helped me. I've already created the project from scratch, which didn't help either. I don't know what to do next and I hope someone can help me here.</p>
  <p>thanks in advance</p>
  <pre><code>library IEEE;
  use IEEE.STD_LOGIC_1164.ALL;
  use IEEE.STD_LOGIC_arith.ALL;
  use IEEE.STD_LOGIC_signed.ALL;
  use IEEE.STD_LOGIC_unsigned.ALL;
  use IEEE.NUMERIC_STD.ALL;
  
  
  
  entity ParallelAdaptor is
      Port ( A1 : in STD_LOGIC;
             A2 : in STD_LOGIC;
             A3 : in STD_LOGIC;
             c1 : in STD_LOGIC;
             B1 : out STD_LOGIC;
             B2 : out STD_LOGIC;
             B3 : out STD_LOGIC);
  end ParallelAdaptor;
  
  architecture Behavioral of ParallelAdaptor is
  
  begin
  
      B1 &lt;= (-c1 * (A3 + A1) + A3 + A2 - A1);
  
  
  end Behavioral;
  </code></pre>