This expression is used inside the braces {} that define the index of the summation. The syntax for an expression is

这个表达式在花括号（{}）中使用，它定义了和的索引。

youdao

Since a dummy index just indicates summation, it is immaterial which symbol is used.

由于哑指标只是表明求和，所以它使用什么符号是无关重要的。

youdao

Then in the index compared Linklist have the same index, if the same index, then the corresponding coefficient for peace, and the summation of the results of merging llist2;

然后再在指数链表中比较有没有相同的指数，如果有相同的指数，那就把相对应的系数进行求和，并把求和结果归并到llist2中；

youdao