[−][src]Crate logos
Create ridiculously fast Lexers.
Logos works by:
- Resolving all logical branching of token definitions into a tree.
- Optimizing complex patterns into Lookup Tables.
- Always using a Lookup Table for the first byte of a token.
- Producing code that never backtracks, thus running at linear time or close to it.
In practice it means that for most grammars the lexing performance is virtually unaffected by the number of tokens defined in the grammar. Or, in other words, it is really fast.
Example
extern crate logos; use logos::Logos; #[derive(Logos, Debug, PartialEq)] enum Token { // Logos requires that we define two default variants, // one for end of input source, #[end] End, // ...and one for errors. Those can be named anything // you wish as long as the attributes are there. #[error] Error, // Tokens can be literal strings, of any length. #[token = "fast"] Fast, #[token = "."] Period, // Or regular expressions. #[regex = "[a-zA-Z]+"] Text, } fn main() { let mut lexer = Token::lexer("Create ridiculously fast Lexers."); assert_eq!(lexer.token, Token::Text); assert_eq!(lexer.slice(), "Create"); assert_eq!(lexer.range(), 0..6); lexer.advance(); assert_eq!(lexer.token, Token::Text); assert_eq!(lexer.slice(), "ridiculously"); assert_eq!(lexer.range(), 7..19); lexer.advance(); assert_eq!(lexer.token, Token::Fast); assert_eq!(lexer.slice(), "fast"); assert_eq!(lexer.range(), 20..24); lexer.advance(); assert_eq!(lexer.token, Token::Text); assert_eq!(lexer.slice(), "Lexers"); assert_eq!(lexer.range(), 25..31); lexer.advance(); assert_eq!(lexer.token, Token::Period); assert_eq!(lexer.slice(), "."); assert_eq!(lexer.range(), 31..32); lexer.advance(); assert_eq!(lexer.token, Token::End); }
Re-exports
pub use logos_derive::Logos; |
pub use self::source::Source; |
pub use self::source::Slice; |
Modules
source | This module contains a bunch of traits necessary for processing byte strings. |
Macros
lookup | Macro for creating lookup tables where index matches the token variant
as |
Structs
Lexer |
|
Traits
Extras | Helper trait that can be injected into the |
Logos | Trait implemented for an enum representing all tokens. You should never have
to implement it manually, use the |
Type Definitions
Lexicon | A Lookup Table used internally. It maps indices for every valid
byte to a function that takes a mutable reference to the |