libskry_r VS barre

As already mentioned, bounds checks won't necessarily cause that much overhead. When I rewrote my small image processing library from C to Rust ([1]), I only had to use unchecked array access in one hot loop to get overall performance equivalent to C code.

[1] https://github.com/GreatAttractor/libskry_r

To practise Rust, I rewrote my small C99 library in it [1]. Performance is more or less the same, I only had to use unchecked array access in one small hot loop (details in README.md). I haven't ported multithreading yet, but I expect Rust's Rayon parallel iterators will likewise be comparable to OpenMP.

[1] https://github.com/GreatAttractor/libskry_r

I've made some attempts, but nothing production grade.

About large character classes: how are those harder than in approaches? If you build any FSM you have to deal with those, don't you?

One way to handle them that works well when the characters in your classes are mostly next to each other unicode, is to express your state transition function as an 'interval map'

What I mean is that eg a hash table or an array lets you build representations of mathematical functions that map points to values.

You want something that can model a step function.

You can either roll your own, or write something around a sorted-map data structure.

Eg in C++ you'd base the whole thing around https://en.cppreference.com/w/cpp/container/map/upper_bound (or https://hackage.haskell.org/package/containers-0.4.0.0/docs/... in Haskell.)

The keys in your sorted map are the 'edges' of your characters classes (eg where they start and end).

Does that make sense? Or am I misunderstanding the problem?

> I personally always get stuck at how to handle things like captures [...]

Let me think about that one for a while. Some Googling suggests https://github.com/elfsternberg/barre though