title: Two's complement VHDL
body: <p>I am just trying to make a simple two's complement device in VHDL but it is throwing back this really annoying error and I'm unsure what I have done wrong. Probably something very silly...The error is
  "Error (10327): VHDL error at twocompliment.vhd(21): can't determine definition of operator ""nand"" -- found 0 possible definitions"</p>
  
  <p>The code is</p>
  
  <pre><code>library ieee;
  use ieee.std_logic_1164.all; 
  use ieee.numeric_std.all;
  entity twoscompliment is
        generic
        (
                Nbits : positive := 8 
         );
   port 
  ( 
             --Inputs
             A : in std_logic_vector (Nbits-1 downto 0);
             --Outputs
             Y : out std_logic_vector (Nbits downto 0)
  );
  end twoscompliment;
  
  architecture twoscompliment_v1 of twoscompliment is
   begin
    Y &lt;= std_logic_vector(unsigned(A NAND '1') + '1');
   end twoscompliment_v1;
  </code></pre>
  
  <p>Any help would be awesome!</p>