第一次调用udf的时候，需要初始化groupmap属性，然后再继续正常调用过程中的一般性处理。

In the first call to the UDF, we need to initialize the groupMap attribute and continue with the usual processing for the normal calls.

youdao

可以使用初始化器列表对标量变量进行初始化，在这种情况下应用一般的类型窄化规则。

It's okay to use initializer lists to initialize scalar variables, and the usual rule of type narrowing applies in such cases.

youdao

还假定了一个初始时间，初始时间一般都可以设成零。

And we've also assumed an initial time, which usually we can just call zero.

youdao

Because here what we have is some atom that we're studying, in the case, it's going to be a gas, and we hit it with a photon that has some incident energy.

因为这里我们要研究的是一些原子,在这种情况下，一般是气态的，然后我们令一个,具有一定初始能量的光子打上去。

麻省理工公开课 - 化学原理课程节选