class RuboCop::Cop::Style::NumericLiterals

def format_number(node)
  int_part, float_part = node.source.split('.')
  int_part = int_part.to_i
  formatted_int = int_part
                  .abs
                  .to_s
                  .reverse
                  .gsub(/...(?=.)/, '\&_')
                  .reverse
  formatted_int.insert(0, '-') if int_part < 0
  if float_part
    format('%s.%s', formatted_int, float_part)
  else
    formatted_int
  end
end