anchor.diff: -{ lib, stdenv
  +{ lib
  +, stdenv
   , fetchurl
   , gsl
   , mpfr
  
positive.code:     license = licenses.unfree;
      maintainers = with maintainers; [ prusnak ];
      platforms = platforms.unix;
    };
  }
  
negative.code: 
  stdenv.mkDerivation rec {
    pname = "ViennaRNA";
    version = "2.4.18";
  
    src = fetchurl {
      url = "https://www.tbi.univie.ac.at/RNA/download/sourcecode/2_4_x/${pname}-${version}.tar.gz";
      sha256 = "17b0mcfkms0gn1a3faa4cakig65k9nk282x6mdh1mmjwbqzp5akw";
    };
  
    buildInputs = [
  