.pick 在 Mix 上不受支持?

.pick not supported on a Mix?

我正在尝试这个:

 my Mix $mix = { foo => 3.5, bar => 2.5}.Mix; 
 say $mix.pick

理论上应该可行,因为 a Mix does Baggy, and Baggy does pick。但是,我收到错误消息:

.pick is not supported on a Mix

知道为什么它不受支持吗?我应该使用什么替代方案?

Any idea why it's not supported?

也许:

lizmat     TimToady: .pick($n > 1) on a MixHash, how would that work? I assume it won't work? What to deduct for a chosen key?
lizmat     (or on a Mix, for that matter)
TimToady   I don't we need to support .pick on a Mix until someone comes up with a real use case

来自http://colabti.org/irclogger/irclogger_log/perl6?date=2013-10-03#l1369

What alternative should I use?

我怀疑是 "write your own"。