Avoid concrete fields in traits that can't be initialized to suitable default values.

在trait里避免不能用合适的默认值初始化的具体字段。

youdao

Note that, in this example, sum must be initialized to an explicit floating-point value; otherwise, all the subsequent computations will be done using integer arithmetic.

注意，在本例中，sum 必须被初始化为一个显式的浮点值；否则，所有后续计算都将使用整数运算计算。

youdao

All right. Second question: or maybe a better way of saying this, and the general format you're likely to see here is, a test involving a variable name, which must be initialized outside of the loop, and which interior to the loop gets changed, so that the test is going to change.

好，第二个问题：,换种更好的方式来说吧，你们通常喜欢的,方式是，这个测试涉及到一个变量名字，变量在循环外已经被初始化，然后循环内部会改变这个变量的值，因此测试结果会改变。

麻省理工公开课 - 计算机科学及编程导论课程节选