3 ms·

Regular expressions: Rust vs. F# vs. Scala vs. D

5 points by yawniek 11y ago

weinzierl 11y ago
Regarding performance Rust is the loser in this comparison. The regex crate documentation addresses this issue and says this is because of a lack of optimization. Generally I really like the fresh approach that Rust takes on the regex topic. I can't explain it better than the docs: This crate provides a native implementation of regular expressions that is heavily based on RE2 both in syntax and in implementation. Notably, backreferences and arbitrary lookahead/lookbehind assertions are not provided. In return, regular expression searching provided by this package has excellent worst-case performance. [...] Rust's compile-time meta-programming facilities provide a way to write a regex! macro which compiles regular expressions when your program compiles. Said differently, if you only use regex! to build regular expressions in your program, then your program cannot compile with an invalid regular expression. Moreover, the regex! macro compiles the given expression to native Rust code, which ideally makes it faster. Unfortunately (or fortunately), the dynamic implementation has had a lot more optimization work put into it currently, so it is faster than the regex! macro in most cases. http://doc.rust-lang.org/regex/regex/index.html http://doc.rust-lang.org/regex/regex/index.html
- burntsushi 11y ago
  The regex crate actually has quite a bit of optimization, which is why it's #1 on the benchmark game. In the OP, it looks like Rust is holding its own to me. Just because Rust's regexes use automata doesn't mean they have to be slow. :-) It can be tricky to make them fast, but RE2 proves that it is possible!
chenglou 11y ago
Would be nice to have JS' speed (V8)! Last time I checked they compile the regex into some really clever heuristics. I wouldn't be surprised if the speed is on par or faster than what's here. http://blog.chromium.org/2009/02/irregexp-google-chromes-new-regexp.html?m=1 http://blog.chromium.org/2009/02/irregexp-google-chromes-new...

5 points by yawniek 11y ago

Regarding performance Rust is the loser in this comparison. The regex crate documentation addresses this issue and says this is because of a lack of optimization. Generally I really like the fresh approach that Rust takes on the regex topic. I can't explain it better than the docs: This crate provides a native implementation of regular expressions that is heavily based on RE2 both in syntax and in implementation. Notably, backreferences and arbitrary lookahead/lookbehind assertions are not provided. In return, regular expression searching provided by this package has excellent worst-case performance. [...] Rust's compile-time meta-programming facilities provide a way to write a regex! macro which compiles regular expressions when your program compiles. Said differently, if you only use regex! to build regular expressions in your program, then your program cannot compile with an invalid regular expression. Moreover, the regex! macro compiles the given expression to native Rust code, which ideally makes it faster. Unfortunately (or fortunately), the dynamic implementation has had a lot more optimization work put into it currently, so it is faster than the regex! macro in most cases. http://doc.rust-lang.org/regex/regex/index.html http://doc.rust-lang.org/regex/regex/index.html

burntsushi 11y ago
The regex crate actually has quite a bit of optimization, which is why it's #1 on the benchmark game. In the OP, it looks like Rust is holding its own to me. Just because Rust's regexes use automata doesn't mean they have to be slow. :-) It can be tricky to make them fast, but RE2 proves that it is possible!

chenglou 11y ago

Would be nice to have JS' speed (V8)! Last time I checked they compile the regex into some really clever heuristics. I wouldn't be surprised if the speed is on par or faster than what's here. http://blog.chromium.org/2009/02/irregexp-google-chromes-new-regexp.html?m=1 http://blog.chromium.org/2009/02/irregexp-google-chromes-new...