anchor.diff:  
   ## Haskell environment
   ENV PATH $HOME/local/.bin:$PATH
  -ENV STACK stack
  +ENV STACK stack --no-terminal
   ENV STACK_WORKDIR /opt/stack
   
   ## Copy across stack.yaml
  
positive.code: 
  ## Command-line tools
  WORKDIR $STACK_WORKDIR
  RUN $STACK setup; 
  RUN $STACK install \
      pandoc \
      stylish-haskell \
  
negative.code: 
  ENV LTS_VERSION lts-5.5
  
  ## Basic dependencies
  RUN yum install git gcc gcc-c++ gmp-devel zlib-devel libstdc++-devel -y
  
  ## Fetch and install stack
  