Exclude a Pattern in regex When Matching Another Pattern

[Sophanatprime]

Hello everyone,

I have a question regarding the use of regex in Rust. Is it possible to match a certain pattern while excluding another pattern? For instance, I want to match the pattern a.c.e but exclude matches like abcde. I understand that in this specific case, the equivalent pattern would be a[^b]c[^d]e, but for many patterns, it might not be possible to write a completely equivalent pattern.

I am aware that within Character classes, the -- Direct subtraction operator can be used. However, since ( is treated as a literal in Character classes, I cannot write something like [(?:a.c.e)--(?:abcde)].

Is there any way to achieve this exclusion in Rust's regex? Any guidance or suggestions would be greatly appreciated.

Thank you!

[BurntSushi]

What you're looking for is a way to represent the "complement" of a regex. While that operation (along with intersection) is closed under regular languages, and this crate only supports patterns expressing a regular language, this crate does not support either (complement or intersection). You'll need to write out the complement yourself (which is often tricky and very large) or match a second regex (which isn't always possible depending on what you're doing, but usually is).

[Sophanatprime]

Thank you for the very fast reply.