anchor.diff:  RUN ruby-build $RUBY_VERSION $RUBY_DIR
   
   RUN gem install bundler cztop iruby pry pry-doc awesome_print gnuplot rubyvis nyaplot --no-document && \
  -#RUN gem update --no-document --system && gem install --no-document sciruby-full && \
       iruby register --force
   
   # brendan-rius/jupyter-c-kernel
  
positive.code:     libtool libffi-dev make automake \
      libssl-dev libreadline-dev zlib1g-dev \
      git libzmq-dev autoconf pkg-config && \
  #    build-essential git libssl-dev libreadline-dev libffi-dev pkg-config libzmq-dev gnuplot-nox libgsl0-dev libtool autoconf automake zlib1g-dev libsqlite3-dev libmagick++-dev imagemagick libatlas-base-dev && \
      apt-get clean && \
      rm -rf /var/lib/apt/lists/*
  
  
negative.code: ENV SAGE_BIN_FILE sage-$SAGE_VER-Ubuntu_16.04-x86_64.tar.bz2
  ENV SAGE_ROOT /opt/sage/$SAGE_VER
  RUN mkdir -p $SAGE_ROOT && chown $NB_USER:users $SAGE_ROOT
  RUN apt-get update && \
      apt-get install -y --no-install-recommends bsdtar && \
      apt-get autoclean && \
      apt-get clean && \
      rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*
  
  USER $NB_USER
  WORKDIR $SAGE_ROOT
  RUN wget -nv http://mirrors.mit.edu/sage/linux/64bit/$SAGE_BIN_FILE && \
      bsdtar -xjf $SAGE_BIN_FILE --strip-components=1 && \
      rm $SAGE_BIN_FILE
  
  USER root
  RUN ln -sf $SAGE_ROOT/sage /usr/bin/sage && \
      ln -sf $SAGE_ROOT/sage /usr/bin/sagemath
  
  ADD ./add_sage/post.py $SAGE_ROOT/post.py
  