fst VS redgrep

I'd point you towards BurntSushi's fst crate: https://github.com/BurntSushi/fst

The fst crate effectively relies on mmap for it to work right. The folks here suggesting you just use the heap might be right, but only if using the heap is actually plausible. If your dictionary is GBs big (an FST might be bigger than available memory), then copying it the heap first would be disastrous.

You'll love what we're working on if you're interested in the implementation of:- Tantivy- Meilisearch- Finite State Transducers

Here's an example of longest prefix matching using a FST which I based my approach on: https://github.com/BurntSushi/fst/pull/104/files

Finite State Transducers

As a result, I have a plan to implement a desktop version from then and I finished today with a beta version. The desktop is based on tauri, and the dictionary index algorithm is FST (it is an awesome index algorithm).

WordBueno’s data is currently derived from Wiktionary. The backend is using Rust’s warp with fst for indexing.

No you don't. I've written multiple programs that load things instantly off the file system via memory maps. See the fst crate[1], for example, which is designed to work with memory maps.

Rust "works badly with memory mapped files" doesn't mean, "Rust can't use memory mapped files." It means, "it is difficult to reconcile Rust's safety story with memory maps." ripgrep for example uses memory maps because they are faster sometimes, and its safety contract[2] is a bit strained. But it works.

[1] - https://github.com/BurntSushi/fst/

[2] - https://docs.rs/grep-searcher/0.1.7/grep_searcher/struct.Mma...

I don't think Rust regex engine relies on this technique. I guess the main point is when you construct the DFA directly you still have the possibility of the exponential explosion of the number of states. That's why modern engines balance between NFA/DFA and lazy DFA.

Though there is an implementation that relies only on Brzozowski derivatives: https://github.com/google/redgrep

redgrep did it though: https://github.com/google/redgrep

It couldn't figure it out from looking through ripgrep's website: does ripgrep support intersection and complement of expressions? Like eg https://github.com/google/redgrep does.

Regular languages are closed under those operations after all.