https://github.com/mirryi/regexp2

Toy regular expressions implementation using finite automata.
https://github.com/mirryi/regexp2

automata regex

Last synced: about 2 months ago
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Toy regular expressions implementation using finite automata.

• Host: GitHub
• URL: https://github.com/mirryi/regexp2
• Owner: mirryi
• License: apache-2.0
• Created: 2021-06-23T23:57:09.000Z (almost 4 years ago)
• Default Branch: master
• Last Pushed: 2022-05-26T03:02:01.000Z (about 3 years ago)
• Last Synced: 2025-02-13T20:17:33.639Z (4 months ago)
• Topics: automata, regex
• Language: Rust
• Homepage:
• Size: 300 KB
• Stars: 0
• Watchers: 1
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE-APACHE

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# RegExp2

A toy regular expressions implementation.

# Usage

The following operators are supported:

-   `*`         : the Kleene star

-   `+`         : the "plus" operator, where `a+` is equivalent to `aa*` or

                  `a*a`

-   `?`         : the optional operator

-   `|`         : the union operator

-   `(` and `)` : grouping

-   \\          : escaping meta-characters

-   `[abc]`     : character classes with character ranges `[A-Z0-9]`

-   `[^abc]`    : negation of character classes

-   `\n`        : newline

-   `\d`, `\D`  : all Unicode decimal number characters and all non-decimal

                  number characters, respectively

-   `\w`, `\W`  : all word characters (alphanumeric and `_`) and non-word

                  characters, respectively

-   `\s`, `\S`  : all whitespace and non-whitespace characters, respectively

-   `.`         : any character except newline (`\n`)

A fairly arbitrary usage example:

```rust

use regexp2::RegExp;

fn main() {

    // Any sequence of a's and b's ending in abb.

    let mut re = RegExp::new("(a|b)*abb").unwrap();

    assert!(re.is_match("abb"));

    assert!(re.is_match("aababb"));

    // Any sequence of characters that are not B, C, D, E, F or any lowercase

    // letter.

    re = RegExp::new("[^B-Fa-z]*").unwrap();

    assert!(re.is_match("AGAQR"));

    // Any sequence of at least one digit followed by nothing or an

    // alphanumeric or underscore.

    re = RegExp::new(r"\d+\w?").unwrap();

    assert!(re.is_match("3a"));

    assert!(re.is_match("08m"));

    assert!(re.is_match("999_"));

}

```