outcome VS RE2

https://github.com/ned14/outcome/tree/develop/abi-compliance uses both in a CI pass to ensure Outcome never changes anything which breaks either API or ABI with earlier versions.

outcome and/or expected

A "Sample Usage" appears on the front page of the docs: https://ned14.github.io/outcome/

I recently came across boost outcome as I was searching for a better error handling method. It took me a minute to get a hang of it but now I love it. After creating my own policy and a few aliases for easier use.

std::optional and std::variant can be a bit awkward to use in this scenario, though. Consider a dedicated type like boost::outcome (standalone versions) or one of the implementations of the proposed std::expected.

Minimum possible compile time impact is a key goal of https://github.com/ned14/outcome. We ship a single header edition which only includes the low impact standard headers as listed at https://github.com/ned14/stl-header-heft. We also don't use union storage for non-TC non-MB types in order to avoid complex metaprogramming execution by the compiler per instantiation.

It's really weird that I wrote the above, and then this bug was reported to Outcome: https://github.com/ned14/outcome/issues/244. Here is my exact complaint about lack of lifetime tracking in C++.

Looking at the benchmark where C++ is worst compared to other languages, it's depending on the library used. I would guess if they used Google's re2 Regex library instead of Boost's, the result would be different.

https://github.com/google/re2

https://github.com/greensoftwarelab/Energy-Languages/blob/ma...

That page says it just includes "some of the most common special characters", and following the link to the Examples page in turn includes a link to the full list.

Python uses backtracking, so this probably isn't O(n), especially with the ability to choose the dictionary.

But with there are non-backtracking matchers which would make this O(n). Here's re2 from https://github.com/google/re2 :

  >>> import re2

RE2 is a Google regular expression library

google's regex library: https://github.com/google/re2

I am currently working with Regex, specifically Re2, and was wondering if there is a real difference between the above expressions for repeated sub-regex.

I ported Google RE2, a regular expression library, to SPVM as Resource::Re2, and created SPVM::Regex, a wrapper for it.

I searched for I found that there is a Perl compatible regular expression called Google RE2. It is written in C++, and with Google RE2, I can use Perl-compatible regular expressions as a library.

Yes, but there is an interesting clarification here. RE2 has used the "caching" approach documented in the Ruby bug ticket linked for quite some time (since its birth?): https://github.com/google/re2/blob/954656f47fe8fb505d4818da1...

It is mentioned only briefly in Cox's article on regex matching in the wild. Look for the word "bitstate": https://swtch.com/~rsc/regexp/regexp3.html

I didn't know Perl had implemented this trick too.

The paper[1] cited in the Ruby bug ticket was published very recently. When I first read the Ruby bug ticket, I immediately wondered how they sidestepped the memory use problem. The paper's abstract seems to suggest there is some technique for doing so, as it rebuffs the idea of doing "full" memoization. Alas, I do not have access the paper. (Which is fucking ridiculous.)

[1]: https://ieeexplore.ieee.org/abstract/document/9519427