def get_eval_file(input)
      input = input.to_s
      unless File.extname(input) == Settings::FILE_EXTENSION
        input += Settings::FILE_EXTENSION
      end
      input
    end
def get_eval_file(input)
      input = input.to_s
      unless File.extname(input) == Settings::FILE_EXTENSION
        input += Settings::FILE_EXTENSION
      end
      input
    end
Add .op extension to input file if it isn't already set.

 @param input [Symbol] Input file