Negate match in RE2 syntax?

Negate match in RE2 syntax?

How can I write a regex in RE2 for “match strings not starting with 4 or 5”?
In PCRE I’d use ^(?!4) but RE2 doesn’t support that syntax.

Solutions/Answers:

Solution 1:

You can use this regex:

^[^45]

^ matches start and [^45] matches anything but 4 or 5 at start.

References

Related:  Regex performances between languages or libraries