Error: COMP96_0071: Operator "<operator>" is not defined for such operands

Description

COMP96_0071 is caused by using the undefined %s operator.

entity en is
end;

architecture ar of en is
 signal a : integer;
 signal c : bit_vector(3 downto 0);
 signal d : bit_vector(3 downto 0);
begin
  d<= a+c; --COMP96_0071
end;

Solution

Please do one of the following:

• Declare the + operator for the bit and boolean types.

  entity en is
  end;
  
  architecture ar of en is
    signal a : integer;
    signal c : bit_vector(3 downto 0);
    signal d : integer;
    function "+"(l:integer;r:bit_vector) return integer is
      variable i : integer;
    begin
      --(...)
      return i;
    end function;
  begin
    d<= a+c;
  end;
  

• Convert the type operator to a type where the operator is defined.

  entity en is
  end;
  
  architecture ar of en is
    signal a : integer;
    signal c : bit_vector(3 downto 0);
    signal d : integer;
    function conv_func (a:bit_vector) return integer is
      variable i : integer;
    begin
      --()
      return i;
    end function;
  begin
    d<= a+conv_func(c);
  end;
  

• Use the conversion function or the operator from one of the predefined libraries.

  library ieee;
  use ieee.numeric_bit.all;
  entity en is
  end;
  
  architecture ar of en is
    signal a : integer;
    signal c : bit_vector(3 downto 0);
    signal d : integer;
  begin
    d<= a+to_integer(unsigned(c));
  end;