I will agree that the elixir regexes should include the u flag by default and require explicit opt-out. We generally should prefer correctness over speed with ways to opt-in into faster, but potentially incorrect results.

Unfortunately, the soonest we could be able to change this would be 2.0 (and there are no plans for 2.0 at the moment). This is because that would be a breaking change since many functions would start returning different results.

i would challenge the “unicode is not usually needed” assumption. Unless you have complete confidence in your knowledge of the cultural context of your audience, Latin-1 is a poor assumption. And in an Elixir context, the String.t type is unicode so its not surprising that developers are caught out by the default behaviour of Regex being Latin-1 (even though I understand why the choice, I think its hard to justify as the default).

Latin-1 doesn’t even include the Euro symbol. @michalmuskala’s native language can’t be represented in Latin-1 (Polish is Latin-2). And given the global participation of this forum I’d warrant there are many members building applications for a global audience and therefore should not make limited assumptions on character input or output.

I suppose I may be an outlier on this (Australian, living in Singapore, and having worked in several Asian countries for quite a while). It even bugs me that we don’t consistently address José with the name his mother gave him

Elixir is a Unicode-centric language. I think that the :re option "u" should be the default.

With unicode flag:

iex(1)> Regex.match?(~r/\p{Lu}/u, "Ö")
true
iex(2)> Regex.match?(~r/\p{Lu}/u, "ö")
false

Latin comes from the underlying erlang module. u is not the default as it is usually not needed but has measurable impact. Also it makes it easier to simply drop to the erlang regex module.

There was a similar question recently, perhaps the derailed discussion towards the end might help you?

Thats a great contribution, thanks!

Would you think it appropriate to also mention that it supports Unicode category notation? Like

iex> Regex.match? ~r/\p{Lu}\p{Ll}+/, "José"
true

And Unicode Block notation too:

iex> Regex.match? ~r/\p{Latin}+/, "José"
true
iex> Regex.match? ~r/\p{Hiragana}+/, "José"
false
iex> Regex.match? ~r/\p{Cherokee}+/, "José"
false