code: private boolean noInput(Input input) {
  		return input.words().isEmpty()
  				|| (input.words().size() == 1 && input.words().get(0).trim().isEmpty())
  				|| (input.words().iterator().next().matches("\\s*//.*"));
  	}
docs: Return true if the parsed input ends up being empty (<em>e.g.</em> hitting ENTER on an
  empty line or blank space).
  
  <p>
  Also returns true (<em>i.e.</em> ask to ignore) when input starts with {@literal //},
  which is used for comments.
  </p>