anchor.diff:      if stdenv.isi686
       then fetchurl {
         url = "mirror://gnu/mit-scheme/stable.pkg/${version}/mit-scheme-${version}-i386.tar.gz";
  -      sha256 = "1vqdy9f1lbzflr9bw0gjn4g4w3hdpnjrkiwj5aaah70flif5ndns";
  +      sha256 = "1bigzzk0k08lggyzqp4rmyvbqhhs3ld4c7drfp22d5qnkbvvzh4g";
       } else if stdenv.isx86_64
       then fetchurl {
         url = "mirror://gnu/mit-scheme/stable.pkg/${version}/mit-scheme-${version}-x86-64.tar.gz";
  
positive.code: { fetchurl, stdenv, gnum4, texinfo, texLive, automake }:
  
  let
    version = "9.1";
    bootstrapFromC = ! (stdenv.isi686 || stdenv.isx86_64);
  in
  stdenv.mkDerivation {
  
negative.code:       url = "mirror://gnu/mit-scheme/stable.pkg/${version}/mit-scheme-c-${version}.tar.gz";
        sha256 = "1661cybycfvjjyq92gb3n1cygxfmfjdhnh3d2ha3vy6xxk9d7za9";
      };
  
    buildPhase =
      '' cd src
  