anchor.diff:      description = "Advanced purely-functional web programming language";
       homepage    = "http://www.impredicative.com/ur/";
       license     = stdenv.lib.licenses.bsd3;
  -    platforms   = stdenv.lib.platforms.linux;
  +    platforms   = stdenv.lib.platforms.linux ++ stdenv.lib.platforms.darwin;
       maintainers = [ stdenv.lib.maintainers.thoughtpolice stdenv.lib.maintainers.sheganinans ];
     };
   }
  
positive.code:   configureFlags = "--with-openssl=${openssl.dev}";
  
    preConfigure = ''
      export PGHEADER="${postgresql}/include/libpq-fe.h";
      export MSHEADER="${lib.getDev mysql.client}/include/mysql/mysql.h";
      export SQHEADER="${sqlite.dev}/include/sqlite3.h";
  
      export CCARGS="-I$out/include \
                     -L${lib.getLib mysql.client}/lib/mysql \
                     -L${postgresql.lib}/lib \
                     -L${sqlite.out}/lib";
    '';
  
negative.code: { stdenv, lib, fetchurl, file, openssl, mlton
  , mysql, postgresql, sqlite, gcc
  }:
  
  stdenv.mkDerivation rec {
  