Note that the index variable ( {i in TOY} ) comes before the :.

注意索引变量（{i in TOY}）都是在 : 之前出现的。

youdao

Try to use a differently named index variable for each set consistently; it's a good idea, especially when debugging.

我们可以试图为每个集合使用不同的命名索引变量；这是一个好主意，尤其是在进行调试时更为突出。

youdao

Note that the row and column order is the same as the element order in each set, and the index variable names are consistent between lines 12, 13, and 14.

注意行和列的次序与元素在每个集合中的顺序是相同的，索引变量名在第12、13和14行是一致的。

youdao

Well, the bracket notation means you can index into this variable.

好的，这个括号的意思是你可以,索引这个变量。

哈佛公开课 - 计算机科学课程节选

Now I seem to be violating my own mantra here by just calling this variable A, but this is reasonable, I much as with four loops when you just call an incrementing variable I, because you just need an index, well, same here.

现在我好像违背了我自己的意愿,我把这个变量叫做A，但这是合理的，就像我们的for循环中，我们把一个增变量叫做,因为我们只要一个索引，这里也一样。

哈佛公开课 - 计算机科学课程节选

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