anchor.diff:  ENV NPM_VERSION 2.1.16
   
   RUN curl -SLO "http://nodejs.org/dist/v$NODE_VERSION/node-v$NODE_VERSION-linux-x64.tar.gz" \
  -  && curl -SLO "http://nodejs.org/dist/v$NODE_VERSION/SHASUMS256.txt.asc" \
  -  && gpg --verify SHASUMS256.txt.asc \
  -  && grep " node-v$NODE_VERSION-linux-x64.tar.gz\$" SHASUMS256.txt.asc | sha256sum -c - \
  -  && tar -xzf "node-v$NODE_VERSION-linux-x64.tar.gz" -C /usr/local --strip-components=1 \
  -  && rm "node-v$NODE_VERSION-linux-x64.tar.gz" SHASUMS256.txt.asc \
  -  && npm install -g npm@"$NPM_VERSION" \
  -  && npm cache clear
  + && curl -SLO "http://nodejs.org/dist/v$NODE_VERSION/SHASUMS256.txt.asc" \
  + && gpg --verify SHASUMS256.txt.asc \
  + && grep " node-v$NODE_VERSION-linux-x64.tar.gz\$" SHASUMS256.txt.asc | sha256sum -c - \
  + && tar -xzf "node-v$NODE_VERSION-linux-x64.tar.gz" -C /usr/local --strip-components=1 \
  + && rm "node-v$NODE_VERSION-linux-x64.tar.gz" SHASUMS256.txt.asc \
  + && npm install -g npm@"$NPM_VERSION" \
  + && npm cache clear
   
   ### Ruby
   RUN apt-get update && apt-get install -y \
       curl \
       procps \
  -  && rm -rf /var/lib/apt/lists/*
  + && rm -rf /var/lib/apt/lists/*
   
   ENV RUBY_MAJOR 2.2
   ENV RUBY_VERSION 2.2.0
  
positive.code: RUN set -x \
   && mkdir -p /usr/src/python \
   && curl -SL "https://www.python.org/ftp/python/$PYTHON_VERSION/Python-$PYTHON_VERSION.tar.xz" \
     | tar -xJC /usr/src/python --strip-components=1 \
   && cd /usr/src/python \
   && ./configure --enable-shared \
   && make -j$(nproc) \
  
negative.code: # some of ruby's build scripts are written in ruby
  # we purge this later to make sure our final image uses what we just built
  RUN apt-get update \
    && apt-get install -y \
       bison \
       ruby \
    && rm -rf /var/lib/apt/lists/* \
    && mkdir -p /usr/src/ruby \
    && curl -SL "http://cache.ruby-lang.org/pub/ruby/$RUBY_MAJOR/ruby-$RUBY_VERSION.tar.bz2" \
     | tar -xjC /usr/src/ruby --strip-components=1 \
    && cd /usr/src/ruby \
    && autoconf \
    && ./configure --disable-install-doc \
  