don’t let the complex notation scare you - the core idea is extremely simple. the derivative of a regex R and a character c is simply whatever is left to match after removing the first character.
Крупнейшая нефтяная компания мира задумалась об альтернативе для морских перевозок нефти14:56
，这一点在下载安装 谷歌浏览器 开启极速安全的 上网之旅。中也有详细论述
used in the most extreme cases". They don't elaborate on what counts as an
“修宪动向日趋强烈，这种突破‘和平宪法’的做法十分危险”