module Utils::IRB::Shell

def irb_time_watch(duration = 1)
  start = Time.now
  pre = nil
  loop do
    cur = [ yield ].flatten
    unless pre
      pre = cur.map(&:to_f)
      cur = [ yield ].flatten
    end
    expired = Time.now - start
    diffs = cur.zip(pre).map { |c, p| c - p }
    rates = diffs.map { |d| d / duration }
    warn "#{expired} #{cur.zip(rates, diffs).map(&:inspect) * ' '} # / per sec."
    pre = cur.map(&:to_f)
    sleep duration
  end
end