按概率随机选取, 使用Hash table, 键=>相对概率, sonic-pi测试通过

按概率随机选取.rb

# base from https://stackoverflow.com/a/19265735/9191373
def picker(options)
  current, max = 0, options.values.inject(:+)
  random_value = rrand(0,max)
  options.each do |key,val|
    current += val
    return key if random_value <= current
  end
end

opti = {:C4=>1, :D4=>2, :E4=>3 }
9.times do
  play picker(opti)
  sleep 0.25
end