a very common use case for regexes is to find matches that are preceded or followed by some context. a classical example being all lines that end with ‘a’. this requirement is usually expressed with a lookahead, where upon finding an ‘a’, you look ahead to check if it’s the end of the line. in a backtracking engine, this is very easy to implement - you just duct-tape the logic that checks the next character, but in a DFA-based engine, this is impossible because you cannot report “the match is here” if the next character is not even known yet. and by the time you know the next character, the position information is lost, so you can’t report the match retroactively (well, unless the distance is fixed of course..).
而在特朗普任內，失業率其實略微上升——從2024年12月（拜登任內最後一個完整月份）的4.1%，上升至2026年1月的4.3%。
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Cosmic rays hit computer RAM all the time. If your RAM is not ECC protected, it will likely flip a random bit. A single bit in billions of bits. Does it matter? Yes. Yes it does.
Each block in the chain has an exact timestamp and can't be changed.