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use std::cmp::Eq;
#[derive(Debug)]
pub struct Automaton<T>
where T: Eq {
states: Vec<StateData>,
edges: Vec<EdgeData<T>>,
start: StateIndex,
current: StateIndex,
end: Vec<StateIndex>,
}
pub type StateIndex = usize;
#[derive(Debug)]
struct StateData {
first_edge: Option<EdgeIndex>,
}
pub type EdgeIndex = usize;
#[derive(Debug)]
struct EdgeData<T>
where T: Eq {
value: T,
target: StateIndex,
next_brother_edge: Option<EdgeIndex>,
}
#[derive(PartialEq, Eq, Copy, Clone, Debug)]
struct State {
id: usize,
end: bool
}
impl<T> Automaton<T>
where T: Eq {
pub fn new() -> Self {
let first_state = StateData { first_edge: None };
Automaton {
states: vec![first_state],
edges: Vec::new(),
start: 0,
current: 0,
end: Vec::new(),
}
}
pub fn add_state(&mut self) -> StateIndex {
let index = self.states.len();
self.states.push(StateData {
first_edge: None,
});
index
}
pub fn add_edge(&mut self, source: StateIndex, target: StateIndex, value: T) {
let edge_index = self.edges.len();
let state_data = &mut self.states[source];
self.edges.push(EdgeData {
value,
target,
next_brother_edge: state_data.first_edge,
});
state_data.first_edge = Some(edge_index);
}
pub fn set_start(&mut self, new_start: StateIndex) {
self.start = new_start;
self.current = new_start;
}
pub fn add_end(&mut self, new_end: StateIndex) {
self.end.push(new_end);
}
pub fn consume(&mut self, val: T) {
let state = &self.states[self.current];
if let Some(edge) = state.first_edge {
if self.edges[edge].value == val {
self.current = self.edges[edge].target;
return;
}
while let Some(edge) = self.edges[edge].next_brother_edge {
if self.edges[edge].value == val {
self.current = self.edges[edge].target;
return;
}
}
}
}
pub fn restart(&mut self){
self.current = self.start;
}
pub fn accepted(&self) -> bool {
self.end.contains(&self.current)
}
pub fn current(&self) -> StateIndex {
self.current
}
}
#[cfg(test)]
mod test {
use super::*;
#[test]
fn test_dfa() {
let mut dfa = Automaton::new();
let s0 = dfa.add_state();
let s1 = dfa.add_state();
dfa.set_start(s0);
dfa.add_end(s1);
assert_eq!(s0, dfa.start);
dfa.add_edge(s0, s1, 10);
dfa.add_edge(s1, s0, 15);
assert_eq!(s0, dfa.current());
dfa.consume(1);
assert_eq!(s0, dfa.current());
dfa.consume(10);
assert_eq!(s1, dfa.current());
assert_eq!(true, dfa.accepted());
dfa.restart();
assert_eq!(s0, dfa.current());
}
}