rsaeb 0.8.0

A no_std + alloc interpreter for A=B ordered rewrite programs.
Documentation 
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

use super::once::{MatchedRuleCommit, OnceStateSet};
use super::state::{MatchedStateSpan, State};
use crate::inspect::{RulePosition, RulePositions};
use crate::rule::{Rule, RuleAnchorSyntax};

#[derive(Debug)]
pub(crate) enum RuleSearch<'program, 'once> {
    Matched(MatchedRule<'program, 'once>),
    Stable,
}

#[derive(Debug)]
pub(crate) struct MatchedRule<'program, 'once> {
    pub(crate) position: RulePosition,
    pub(crate) rule: &'program Rule,
    pub(crate) commit: MatchedRuleCommit<'once>,
    pub(crate) state_match: MatchedStateSpan,
}

#[derive(Debug, Clone, Copy)]
struct MatchedRuleCandidate<'program> {
    position: RulePosition,
    rule: &'program Rule,
    state_match: MatchedStateSpan,
}

pub(crate) fn find_next_match<'program, 'once>(
    rules: &'program [Rule],
    once_states: &'once mut OnceStateSet,
    state: &State,
) -> RuleSearch<'program, 'once> {
    let Some(candidate) = find_next_match_candidate(rules, once_states, state) else {
        return RuleSearch::Stable;
    };

    let Some(commit) = once_states.matched_commit_for_rule(candidate.rule) else {
        return RuleSearch::Stable;
    };

    RuleSearch::Matched(MatchedRule {
        position: candidate.position,
        rule: candidate.rule,
        commit,
        state_match: candidate.state_match,
    })
}

fn find_next_match_candidate<'program>(
    rules: &'program [Rule],
    once_states: &OnceStateSet,
    state: &State,
) -> Option<MatchedRuleCandidate<'program>> {
    for (rule, position) in rules.iter().zip(RulePositions::new()) {
        let Some(state_match) = find_match(state, rule) else {
            continue;
        };

        if !once_states.rule_can_commit(rule) {
            continue;
        }

        return Some(MatchedRuleCandidate {
            position,
            rule,
            state_match,
        });
    }

    None
}

fn find_match(state: &State, rule: &Rule) -> Option<MatchedStateSpan> {
    match rule.anchor() {
        RuleAnchorSyntax::Anywhere => state.find_payload(rule.lhs()),
        RuleAnchorSyntax::Start => state.starts_with_payload(rule.lhs()),
        RuleAnchorSyntax::End => state.ends_with_payload(rule.lhs()),
    }
}