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
use std::mem;
use std::rc::Rc;
#[derive(Debug)]
pub struct ParseTree<K> {
pub kind: K,
pub span: Span,
pub child: Option<Rc<ParseTree<K>>>,
pub sibling: Option<Rc<ParseTree<K>>>,
}
#[derive(Debug)]
pub struct Span {
pub lo: usize,
pub hi: usize,
}
pub const DUMMY_SPAN: Span = Span { lo: 0, hi: 0 };
impl<K> ParseTree<K> {
#[cfg(test)]
fn build(value: K, span: Span, children: Vec<ParseTree<K>>) -> ParseTree<K> {
ParseTree::new(value, span, ParseTree::sibling_chain(children))
}
pub fn new(kind: K, span: Span, child: Option<ParseTree<K>>) -> ParseTree<K> {
let child = child.map(Rc::new);
ParseTree { kind: kind, span: span, child: child, sibling: None }
}
pub fn sibling_chain(mut children: Vec<ParseTree<K>>) -> Option<ParseTree<K>> {
let mut p = match children.pop() {
Some(p) => p,
None => { return None; }
};
while let Some(mut q) = children.pop() {
q.sibling = Some(Rc::new(p));
p = q;
}
Some(p)
}
pub fn add_child_front(&mut self, mut child: ParseTree<K>) {
assert!(child.sibling.is_none());
let old_child = mem::replace(&mut self.child, None);
child.sibling = old_child;
self.child = Some(Rc::new(child));
}
pub fn children(&self) -> ChildIterator<K> {
ChildIterator { next: to_ref(&self.child) }
}
}
fn to_ref<K>(tree: &Option<Rc<ParseTree<K>>>) -> Option<&ParseTree<K>> {
tree.as_ref().map(|t| &**t)
}
pub struct ChildIterator<'tree, K: 'tree> {
next: Option<&'tree ParseTree<K>>
}
impl<'tree, K> Iterator for ChildIterator<'tree, K> {
type Item = &'tree ParseTree<K>;
fn next(&mut self) -> Option<&'tree ParseTree<K>> {
match self.next {
Some(ptr) => {
self.next = to_ref(&ptr.sibling);
Some(ptr)
}
None => None,
}
}
}
impl Span {
pub fn new(lo: usize, hi: usize) -> Span {
Span { lo: lo, hi: hi }
}
}
#[cfg(test)]
mod test {
use super::*;
macro_rules! test_tree {
({ $value:expr; $($children:tt)* }) => {
ParseTree::build($value,
DUMMY_SPAN,
vec![$(test_tree!($children)),*])
}
}
#[test]
fn iterate() {
let tree = test_tree!({22; {44; {66;}} {88;}});
let kids: Vec<_> = tree.children().map(|x| x.kind).collect();
assert_eq!(kids, vec![44, 88]);
}
}