but there’s a problem with the classical formulation. the derivative takes a regex and a character, so to build a state machine you need to compute it for every possible character to get all transitions from a given state. sure, you can compress the number of characters into equivalence classes before, but you still have to compute for each equivalence class - and many of them end up leading to the same state anyway. for example, the regex abc (below) cares about a, b, c, and “everything else”, which brings us down from 65536 to 4 in UTF-16, but for the first node (abc) even b and c behave the same as “everything else”. so what are we computing these for? in other words, there is something left to improve here.
if (result != 0) {
，详情可参考PG官网
Mog supports the standard escape sequences you’d expect:，这一点在手游中也有详细论述
"kind": "Subtract",