yield.rb

def something_slow
  time = Time.now
  puts "I am doing something slow"
  yield
  puts "Elapsed time : #{Time.now - time}"
end


something_slow { sleep(2) }
something_slow { sleep(1) }

# time = Time.now
# puts "I am doing something slow"
# sleep(2)
# puts "Elapsed time : #{Time.now - time}"

# time = Time.now
# puts "I am doing another thing slow"
# sleep(3)
# puts "Elapsed time : #{Time.now - time}"