Degenerate slice indices are handled gracefully: an index that is too large is replaced by the string size, an upper bound smaller than the lower bound returns an empty string.
Degenerate slice indices are handled gracefully: an index that is too large is replaced by the string size, an upper bound smaller than the lower bound returns an empty string.
退化的切片索引处理方式很优美：过大的索引代替为字符串大小，下界比上界大的返回空字符串。