anchor.diff:      "ftp://ftp.metalab.unc.edu/pub/linux/"
     ];
   
  -  # Bioconductor mirrors (from http://bioconductor.org/about/mirrors)
  +  # Bioconductor mirrors (from https://bioconductor.org/about/mirrors/)
     # The commented-out ones don't seem to allow direct package downloads;
     # they serve error messages that result in hash mismatches instead.
     bioc = [
  
positive.code:   gnupg = [
      "https://gnupg.org/ftp/gcrypt/"
      "http://www.ring.gr.jp/pub/net/"
      "http://mirrors.dotsrc.org/gcrypt/"
      "http://ftp.heanet.ie/mirrors/ftp.gnupg.org/gcrypt/"
      "http://www.mirrorservice.org/sites/ftp.gnupg.org/gcrypt/"
    ];
  
    # kernel.org's /pub (/pub/{linux,software}) tree.
    kernel = [
      "http://cdn.kernel.org/pub/"
      "http://linux-kernel.uio.no/pub/"
      "ftp://ftp.funet.fi/pub/mirrors/ftp.kernel.org/pub/"
    ];
  
negative.code:     # http://mirror.aarnet.edu.au/pub/bioconductor/
      # http://watson.nci.nih.gov/bioc_mirror/
      "http://bioconductor.jp/packages/"
      "https://bioconductor.statistik.tu-dortmund.de/packages/"
      "https://mirrors.ustc.edu.cn/bioc/"
    ];
  
    # Hackage mirrors
    hackage = [
      "https://hackage.haskell.org/package/"
    ];
  
    # Roy marples mirrors
    roy = [
      "https://roy.marples.name/downloads/"
      "https://cflags.cc/roy/"
    ];
  
    # Sage mirrors (https://www.sagemath.org/mirrors.html)
    sageupstream = [
      # Africa
      "ftp://ftp.sun.ac.za/pub/mirrors/www.sagemath.org/spkg/upstream/"
      "https://sagemath.mirror.ac.za/spkg/upstream/"
      "https://mirror.ufs.ac.za/sagemath/spkg/upstream/"
  
      # America, North
      "https://mirrors.mit.edu/sage/spkg/upstream/"
      "http://www.cecm.sfu.ca/sage/spkg/upstream/"
      "https://mirrors.xmission.com/sage/spkg/upstream/"
  
  