clojure.core.async / ALTS！ -保证只操作一个通道？

Question

When alts!! or alts! is called, is it guaranteed that only one of the ports are taken from or put into?

(let [[value channel] (alts!! [c1 c2 c3 [1 c4]])]
   (cond (= channel c1)
         ; at this point, is it guaranteed that alts!!
         ; did not take from c2 and c3, and did not call (>!! c4 1)? 
         (do-something)))

I can't find anything relevant about this in the docs. I am guessing it is undefined?

Answer 1

According to alts! 's docstring the function " Completes at most one of several channel operations. [...] ".

This means that only one or zero (ie it will park) operations will be done on the ports when the function is called. Which operation is non-deterministic, as described in the docstring: " Unless the :priority option is true, if more than one port operation is ready a non-deterministic choice will be made ".