1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
|
use crate::regex::RegexToken;
use std::collections::HashMap;
#[derive(Debug, Clone, PartialEq)]
pub enum Trans {
Symbol(char),
Epsilon,
}
#[derive(Debug, Clone, PartialEq)]
struct State {
id: usize,
transitions: Vec<(usize, Trans)>,
}
impl State {
fn new(id: usize) -> Self {
Self {
id,
transitions: Vec::new(),
}
}
}
#[derive(Debug, Clone, PartialEq)]
pub struct NFA {
states: HashMap<usize, State>,
transitions: HashMap<usize, Vec<usize>>,
initial_state: usize,
accepting_states: Vec<usize>,
}
impl NFA {
pub fn new() -> Self {
Self {
states: HashMap::new(),
transitions: HashMap::new(),
initial_state: 0,
accepting_states: Vec::new(),
}
}
pub fn add_state(&mut self) -> usize {
let new_state = State::new(self.states.len());
let id = new_state.id;
self.states.insert(id, new_state);
id
}
pub fn regex_to_nfa_helper(&mut self, input: RegexToken) -> (usize, usize) {
match input {
RegexToken::Symbol(ch) => {
let first = self.add_state();
let last = self.add_state();
self.add_transition(first, last, Trans::Symbol(ch));
(first, last)
}
RegexToken::Concat((left, right)) => {
let first = self.add_state();
let (l_first, l_last) = self.regex_to_nfa_helper(*left);
let (r_first, r_last) = self.regex_to_nfa_helper(*right);
self.add_transition(first, l_first, Trans::Epsilon);
self.add_transition(l_last, r_first, Trans::Epsilon);
(first, r_last)
}
RegexToken::Union((left, right)) => {
let first = self.add_state();
let (l_first, l_last) = self.regex_to_nfa_helper(*left);
let (r_first, r_last) = self.regex_to_nfa_helper(*right);
self.add_transition(first, l_first, Trans::Epsilon);
self.add_transition(first, r_first, Trans::Epsilon);
let last = self.add_state();
self.add_transition(l_last, last, Trans::Epsilon);
self.add_transition(r_last, last, Trans::Epsilon);
(first, last)
RegexToken::Plus(_) => todo!(),
RegexToken::Star(_) => todo!(),
RegexToken::Dot => {
self.add_state();
}
RegexToken::None => {
self.add_state();
}
}
}
pub fn add_transition(&mut self, from: usize, to: usize, trans: char) {
self.transitions
.entry(from)
.and_modify(|val| val.push(to))
.or_insert_with(|| vec![to]);
self.states
.get_mut(&from)
.unwrap()
.transitions
.push((to, trans));
}
fn deduce_accepting_states(&mut self) {
for (id, state) in &self.states {
if state.transitions.is_empty() {
self.accepting_states.push(*id)
}
}
}
pub fn simulate(&mut self, input: String) -> bool {
let mut current = self.states.get(&self.initial_state).unwrap();
let mut chars = input.chars();
'simu: while let Some(nxt) = chars.next() {
println!("current: {current:?}");
for (id, ch) in ¤t.transitions {
println!("nxt: {nxt} ch: {ch}");
if *ch == nxt {
current = self.states.get(id).unwrap();
} else {
break 'simu;
}
}
}
println!("current node: {current:?}");
let current_id = current.id;
self.deduce_accepting_states();
self.accepting_states.iter().any(|&id| id == current_id)
}
}
#[cfg(test)]
mod tests {
use super::*;
use crate::regex::Regex;
#[test]
fn test_simple_succ() {
let input = "abc";
let token = Regex::new(String::from(input));
let mut nfa = NFA::new();
nfa.regex_to_nfa(token);
nfa.add_state();
let inp = "abc";
let output = nfa.simulate(String::from(inp));
assert!(output)
}
#[test]
fn test_simple_fail() {
let input = "abc";
let token = Regex::new(String::from(input));
let mut nfa = NFA::new();
nfa.regex_to_nfa(token);
nfa.add_state();
let inp = "abd";
let output = nfa.simulate(String::from(inp));
assert!(!output)
}
}
|
