class Haml::Exec::Generic

def process_result

so they can run their respective programs.
This is meant to be overridden by subclasses

to appropriate IO streams.
In particular, sets `@options[:input]` and `@options[:output]`
Processes the options set by the command-line arguments. 
def process_result
  input, output = @options[:input], @options[:output]
  input_file, output_file = if input
                              [nil, open_file(@args[0], 'w')]
                            else
                              @options[:filename] = @args[0]
                              [open_file(@args[0]), open_file(@args[1], 'w')]
                            end
  input  ||= input_file
  output ||= output_file
  input  ||= $stdin
  output ||= $stdout
  @options[:input], @options[:output] = input, output
end