The fourth argument is the recursion ID (if there is one), and the last argument is a handle returned by the function that we will need when it is time to de-register.

第四个参数是递归id(如果有的话)，最后一个参数是由取消注册时需要使用的函数返回的句柄。

youdao

This struct is used as an argument to allow methods to poll on it or register a callback to be fired when cancellation is requested. Cancellationtokensource.

这个结构体可作为一个参数，让方法进行轮询，或者注册到一个回调中，在撤销被请求的时候触发。

youdao

The observe method takes anything that can be passed to the :url option of a remote helper as its argument and creates the updateOrientation() method alluded to by the register helper.

observe 方法将获取可以作为实参传递给远程助手的 :url 选项的内容，并且创建由 register 助手暗示的 updateOrientation() 方法。

youdao

Now, a glance at the New Haven Register or Hartford Courant shows that the argument about the death penalty - once thought to be purely academic in this part of America - is very much alive.

BBC: Brutal murders spark death penalty debate