rusty_peg/
tree.rs

1use std::mem;
2use std::rc::Rc;
3
4#[derive(Debug)]
5pub struct ParseTree<K> {
6    pub kind: K,
7    pub span: Span,
8    pub child: Option<Rc<ParseTree<K>>>,
9    pub sibling: Option<Rc<ParseTree<K>>>,
10}
11
12#[derive(Debug)]
13pub struct Span {
14    pub lo: usize,
15    pub hi: usize,
16}
17
18pub const DUMMY_SPAN: Span = Span { lo: 0, hi: 0 };
19
20///////////////////////////////////////////////////////////////////////////
21
22impl<K> ParseTree<K> {
23    #[cfg(test)]
24    fn build(value: K, span: Span, children: Vec<ParseTree<K>>) -> ParseTree<K> {
25        ParseTree::new(value, span, ParseTree::sibling_chain(children))
26    }
27
28    pub fn new(kind: K, span: Span, child: Option<ParseTree<K>>) -> ParseTree<K> {
29        let child = child.map(Rc::new);
30        ParseTree { kind: kind, span: span, child: child, sibling: None }
31    }
32
33    pub fn sibling_chain(mut children: Vec<ParseTree<K>>) -> Option<ParseTree<K>> {
34        let mut p = match children.pop() {
35            Some(p) => p,
36            None => { return None; }
37        };
38        while let Some(mut q) = children.pop() {
39            q.sibling = Some(Rc::new(p));
40            p = q;
41        }
42        Some(p)
43    }
44
45    pub fn add_child_front(&mut self, mut child: ParseTree<K>) {
46        assert!(child.sibling.is_none());
47        let old_child = mem::replace(&mut self.child, None);
48        child.sibling = old_child;
49        self.child = Some(Rc::new(child));
50    }
51
52    pub fn children(&self) -> ChildIterator<K> {
53        ChildIterator { next: to_ref(&self.child) }
54    }
55}
56
57fn to_ref<K>(tree: &Option<Rc<ParseTree<K>>>) -> Option<&ParseTree<K>> {
58    tree.as_ref().map(|t| &**t)
59}
60
61///////////////////////////////////////////////////////////////////////////
62
63pub struct ChildIterator<'tree, K: 'tree> {
64    next: Option<&'tree ParseTree<K>>
65}
66
67impl<'tree, K> Iterator for ChildIterator<'tree, K> {
68    type Item = &'tree ParseTree<K>;
69
70    fn next(&mut self) -> Option<&'tree ParseTree<K>> {
71        match self.next {
72            Some(ptr) => {
73                self.next = to_ref(&ptr.sibling);
74                Some(ptr)
75            }
76            None => None,
77        }
78    }
79}
80
81///////////////////////////////////////////////////////////////////////////
82
83impl Span {
84    pub fn new(lo: usize, hi: usize) -> Span {
85        Span { lo: lo, hi: hi }
86    }
87}
88
89#[cfg(test)]
90mod test {
91    use super::*;
92
93    macro_rules! test_tree {
94        ({ $value:expr; $($children:tt)* }) => {
95            ParseTree::build($value,
96                             DUMMY_SPAN,
97                             vec![$(test_tree!($children)),*])
98        }
99    }
100
101    #[test]
102    fn iterate() {
103        let tree = test_tree!({22; {44; {66;}} {88;}});
104        let kids: Vec<_> = tree.children().map(|x| x.kind).collect();
105        assert_eq!(kids, vec![44, 88]);
106    }
107}
rusty_peg/tree.rs

rusty_peg/
tree.rs
