rand VS regex

Making compatibility promises for distributions means they cannot take advantage of potential advancements in the field.

Defining an error type that is meaningful, portable, and compatible with no-std isn't straightforward. If the std lib's getrandom requires std, then just like that, rand and many other crates won't use it anyway. Using io::Result seems to me to face this challenge.

Some wasm targets can’t generate random numbers at all but in the case of the book because you are using wasm in a browser you can use JS to generate random numbers. I believe there’s a way to get the rand crate to use JS as the backend for generating rand but its a bit more convoluted than the easy one-liner that the book suggests.

rand

This uses rand and xcomplex to handle the mathematics, png to write image files, and dialoguer and indicatif for some pretty prompts and progress bars.

You can often achieve this without any unsafe by putting an assert!() on the length before the hot loop. For example, I got rid of some unsafe in rand that way.

This is a widely used method to map random integers to floating point numbers, but it has the disadvantage of wasting 1 bit of float mantissa precision.

On modern CPUs, its computational advantage over full-precision mapping methods, such as multiplication by a float, is not always clear [1].

[1] https://github.com/rust-random/rand/issues/416

In fact, there are a lot of crates in Rust where in other programming languages, it would be included in the standard library. Examples are regex, random number generators, additional iterator methods, macros for other collections, num traits, loggers, HTTP libraries, error handling, async runtimes, serialization and deserialization, date and time, and many more.

The homepage has a benchmark that compares Zed's "insertion latency" to other editors, and this is the description:

> Open input.rs at the end of line 21 in rust-lang/regex. Type z 10 times, measure how long it takes for each z to display since hitting the z key.

Could someone clarify what that means? My interpretation of that was to go to https://github.com/rust-lang/regex/blob/master/regex-cli/arg... and start typing 'z' at the end of line 21, but that doesn't seem to make any sense. I guess that repo got refactored and those instructions are out of date?

We also used the avenue to sluggify the question title. We used regex to fish out and replace all occurrences of punctuation and symbol characters with an empty string and using the itertools crate, we joined the words back together into a single string, where each word is separated by a hyphen ("-").

Command-Line Rust taught me how to use crates like clap, assert_cmd, and regex. I felt lost before because I didn't know about Rust's ecosystem--which is arguably as important as the language itself. Also, looking up and comparing libraries is a tiring task! blessed.rs is nice but Command-Line Rust really saved me from analysis paralysis.

burntsushi actually regrets making regex replace return a Cow: https://github.com/rust-lang/regex/issues/676#issuecomment-6.... I’m glad it does, and wish it took an impl Into> there, for the reasons discussed in the issue, but burntsushi has a lot more experience of the practical outcomes of this. Just something more to think about.

I'm not familiar with the AoC problem. You might be able to. But RegexSet doesn't give you match offsets.

You can drop down to regex-automata, which does let you do multi-regex search and it will tell you which patterns match[1]. The docs have an example of a simple lexer[2]. But... that will only give you non-overlapping matches.

You can drop down to an even lower level of abstraction and get multi-pattern overlapping matches[3], but it's awkward. The comment there explains that I had initially tried to provide a higher level API for it, but was unsure of what the semantics should be. Getting the starting position in particular is a bit of a wrinkle.

[1]: https://docs.rs/regex-automata/latest/regex_automata/meta/in...

[2]: https://docs.rs/regex-automata/latest/regex_automata/meta/st...

[3]: https://github.com/rust-lang/regex/blob/837fd85e79fac2a4ea64...

It’s not quite that simple, but folks are working on it.

https://github.com/rust-lang/regex/issues/425#issuecomment-1...

https://github.com/helix-editor/helix/pull/211#issuecomment-...

Dependencies used: - regex - unicode_reader - rust decimal - tokio

https://www.cs.princeton.edu/courses/archive/fall19/cos226/l... and https://kean.blog/post/lets-build-regex are excellent introductions to implementing a (very) simplified regex engine: construct a nondetermistic finite state automaton for the regex, then perform a graph search on the resulting digraph; if the vertex corresponding to your end state is reachable, you have a match.

I think this exercise is valuable for anyone writing regexes to not only understand that there's less magic than one might think, but also to visualize a bunch of balls bouncing along an NFA - that bug you inevitably hit in production due to catastrophic backtracking now takes on a physical meaning!

Separately re: the OP, https://github.com/rust-lang/regex/issues/822 (and specifically BurntSushi's comment at the very end of the issue) adds really useful context to the paragraph in the OP about niche APIs: https://blog.burntsushi.net/regex-internals/#problem-request... - searching with multiple regexes simultaneously against a text is both incredibly complex and incredibly useful, and I can't wait to see what the community comes up with for this pattern!