anchor.diff:    };
   }
   
  +
  
positive.code: rec {
    src = fetchurl {
      url = "http://prdownloads.sourceforge.net/sbcl/sbcl-${version}-source.tar.bz2";
      sha256 = "0cs9671jgmn50835m8ccssmq86ssj3pvpd9cjkkq5c3ggm1zddnq";
    };
  
    inherit buildInputs;
  
negative.code: let 
    fetchurl = a.fetchurl;
  
    version = a.lib.attrByPath ["version"] "1.0.29" a; 
    buildInputs = with a; [
      clisp makeWrapper
    ];
  