A procedural macro for building a finite automaton. Main use is for lexing multiple character wide tokens see derive-finite-automaton/examples/main.rs.
Run example:
cd derive-finite-automaton
cargo run --example mainView example macro expansion (requires cargo-expand):
cd derive-finite-automaton
cargo expand --example mainuse derive_finite_automaton::{FiniteAutomata, FiniteAutomataConstructor};
#[derive(FiniteAutomataConstructor, Debug, PartialEq)]
#[automaton_mappings(
"{" => Tokens::OpenBrace,
"}" => Tokens::CloseBrace,
"=" => Tokens::Assign,
"=>" => Tokens::ArrowFunction,
"==" => Tokens::Equal,
"===" => Tokens::StrictEqual,
"." => Tokens::Dot,
"..." => Tokens::Spread,
)]
pub enum Tokens {
OpenBrace,
CloseBrace,
ArrowFunction,
Equal,
StrictEqual,
Assign,
Dot,
Spread,
}You can add conditional mappings with the following
use derive_finite_automaton::FiniteAutomataConstructor;
#[derive(Debug, FiniteAutomataConstructor)]
#[automaton_mappings(
"{" => Tokens::OpenBrace,
"}" => Tokens::CloseBrace,
"=>" => Tokens::ArrowFunction,
"==" => Tokens::Equal,
"===" => Tokens::StrictEqual,
"=" => Tokens::Assign,
// Some mapping
"." => Tokens::Dot,
)]
#[cfg_attr(feature = "special", automaton_mappings(
".?." => Tokens::Magic,
))]
pub enum Tokens {
OpenBrace,
CloseBrace,
ArrowFunction,
Equal,
StrictEqual,
Assign,
Dot,
#[cfg(feature = "special")]
Magic,
}