Crate lazy_regex
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With lazy-regex macros, regular expressions
- are checked at compile time, with clear error messages
- are wrapped in
once_celllazy static initializers so that they’re compiled only once - can hold flags as suffix:
let case_insensitive_regex = regex!("ab*"i); - are defined in a less verbose way
The regex! macro returns references to normal instances of regex::Regex or regex::bytes::Regex so all the usual features are available.
But most often, you won’t even use the regex! macro but the other macros which are specialized for testing a match, replacing, or capturing groups in some common situations:
All of them support the B flag for the regex::bytes::Regex variant.
All macros exist with a bytes_ prefix for building bytes::Regex, so you also have bytes_regex!, regex_is_match!, regex_find!, regex_captures!, regex_replace!, and regex_replace_all!.
Some structs of the regex crate are reexported to ease dependency managment.
Build Regexes
use lazy_regex::regex;
// build a simple regex
let r = regex!("sa+$");
assert_eq!(r.is_match("Saa"), false);
// build a regex with flag(s)
let r = regex!("sa+$"i);
assert_eq!(r.is_match("Saa"), true);
// you can use a raw literal
let r = regex!(r#"^"+$"#);
assert_eq!(r.is_match("\"\""), true);
// or a raw literal with flag(s)
let r = regex!(r#"^\s*("[a-t]*"\s*)+$"#i);
assert_eq!(r.is_match(r#" "Aristote" "Platon" "#), true);
// build a regex that operates on &[u8]
let r = regex!("(byte)?string$"B);
assert_eq!(r.is_match(b"bytestring"), true);
// there's no problem using the multiline definition syntax
let r = regex!(r#"(?x)
(?P<name>\w+)
-
(?P<version>[0-9.]+)
"#);
assert_eq!(r.find("This is lazy_regex-2.2!").unwrap().as_str(), "lazy_regex-2.2");
// (look at the regex_captures! macro to easily extract the groups)
// this line doesn't compile because the regex is invalid:
let r = regex!("(unclosed");
Supported regex flags: i, m, s, x, U, and you may also use B to build a bytes regex.
The following regexes are equivalent:
bytes_regex!("^ab+$"i)bytes_regex!("(?i)^ab+$")regex!("^ab+$"iB)regex!("(?i)^ab+$"B)
They’re all case insensitive instances of regex::bytes::Regex.
Test a match
use lazy_regex::*;
let b = regex_is_match!("[ab]+", "car");
assert_eq!(b, true);
let b = bytes_regex_is_match!("[ab]+", b"car");
assert_eq!(b, true);doc: regex_is_match!
Extract a value
use lazy_regex::regex_find;
let f_word = regex_find!(r#"\bf\w+\b"#, "The fox jumps.");
assert_eq!(f_word, Some("fox"));
let f_word = regex_find!(r#"\bf\w+\b"#B, b"The forest is silent.");
assert_eq!(f_word, Some(b"forest" as &[u8]));doc: regex_find!
Capture
use lazy_regex::regex_captures;
let (_, letter) = regex_captures!("([a-z])[0-9]+"i, "form A42").unwrap();
assert_eq!(letter, "A");
let (whole, name, version) = regex_captures!(
r#"(\w+)-([0-9.]+)"#, // a literal regex
"This is lazy_regex-2.0!", // any expression
).unwrap();
assert_eq!(whole, "lazy_regex-2.0");
assert_eq!(name, "lazy_regex");
assert_eq!(version, "2.0");There’s no limit to the size of the tuple. It’s checked at compile time to ensure you have the right number of capturing groups.
You receive "" for optional groups with no value.
doc: regex_captures!
Replace with captured groups
The regex_replace! and regex_replace_all! macros bring once compilation and compilation time checks to the replace and replace_all functions.
Replacing with a closure
use lazy_regex::regex_replace_all;
let text = "Foo8 fuu3";
let text = regex_replace_all!(
r#"\bf(\w+)(\d)"#i,
text,
|_, name, digit| format!("F<{}>{}", name, digit),
);
assert_eq!(text, "F<oo>8 F<uu>3");The number of arguments given to the closure is checked at compilation time to match the number of groups in the regular expression.
If it doesn’t match you get, at compilation time, a clear error message.
Replacing with another kind of Replacer
use lazy_regex::regex_replace_all;
let text = "UwU";
let output = regex_replace_all!("U", text, "O");
assert_eq!(&output, "OwO");Shared lazy static
When a regular expression is used in several functions, you sometimes don’t want to repeat it but have a shared static instance.
The regex! macro, while being backed by a lazy static regex, returns a reference.
If you want to have a shared lazy static regex, use the lazy_regex! macro:
use lazy_regex::*;
pub static GLOBAL_REX: Lazy<Regex> = lazy_regex!("^ab+$"i);Like for the other macros, the regex is static, checked at compile time, and lazily built at first use.
doc: lazy_regex!
Re-exports
pub use regex;
Macros
- Return an instance of
once_cell::sync::Lazy<bytes::Regex>that you can use in a public static declaration. - Return a lazy static
regex::bytes::Regexchecked at compilation time and built at first use. - Extract captured groups as a tuple of &u8
- Extract the leftmost match of the regex in the second argument as a
&[u8] - Test whether an expression matches a lazy static bytes::Regex regular expression (the regex is checked at compile time)
- Replaces the leftmost match in the second argument using the replacer given as third argument.
- Replaces all non-overlapping matches in the second argument using the replacer given as third argument.
- Return an instance of
once_cell::sync::Lazy<regex::Regex>oronce_cell::sync::Lazy<regex::bytes::Regex>that you can use in a public static declaration. - Return a lazy static Regex checked at compilation time and built at first use.
- Extract captured groups as a tuple of &str.
- Extract the leftmost match of the regex in the second argument, as a
&str, or a&[u8]if theBflag is set. - Test whether an expression matches a lazy static regular expression (the regex is checked at compile time)
- Replaces the leftmost match in the second argument using the replacer given as third argument.
- Replaces all non-overlapping matches in the second argument using the replacer given as third argument.