Quick Start

Build an engine once, then query it as many times as you like. The engine is immutable and cheap to share (&FuzzyAhoCorasick) across threads.

use fuzzy_aho_corasick::{FuzzyAhoCorasickBuilder, FuzzyLimits, SearchOptions};

fn main() {
    // Allow up to 1 edit per match, case-insensitive.
    let engine = FuzzyAhoCorasickBuilder::new()
        .fuzzy(FuzzyLimits::new().edits(1))
        .case_insensitive(true)
        .build(["hello", "world"]);

    // "helllo wolrd" has two typos: an extra 'l' (insertion) and swapped 'lr' (transposition).
    let opts = SearchOptions::new().threshold(0.8).sorted().non_overlapping();
    for m in engine.search("helllo wolrd", &opts).unwrap().iter() {
        println!("matched '{}' as '{}' (score {:.2})", m.pattern, m.text, m.similarity);
    }
    // matched 'hello' as 'helllo' (score 0.90)
    // matched 'world' as 'wolrd' (score 0.90)
}

Three things are happening here:

1. fuzzy(FuzzyLimits::new().edits(1)) — without this the engine only matches exactly. edits(1) lets each match differ from its pattern by at most one edit operation.
2. .threshold(0.8) — the similarity threshold. A candidate is only returned if its score is at least this high. See Scoring & Thresholds.
3. .sorted().non_overlapping() — asks for a ranked set of matches whose spans don’t overlap. SearchOptions bundles the order and overlap strategy for the single search entry point.

Inspecting a match

Each FuzzyMatch tells you what was found and how:

use fuzzy_aho_corasick::{FuzzyAhoCorasickBuilder, FuzzyLimits, SearchOptions};
let engine = FuzzyAhoCorasickBuilder::new().fuzzy(FuzzyLimits::new().edits(1)).build(["needle"]);
for m in engine.search("find the neeedle", &SearchOptions::new().threshold(0.8)).unwrap().iter() {
    println!(
        "pattern #{} ({}) matched bytes {}..{} = {:?}",
        m.pattern_index, m.pattern, m.start, m.end, m.text,
    );
    println!(
        "  score {:.2}, edits {} (ins {}, del {}, sub {}, swap {})",
        m.similarity, m.edits, m.insertions, m.deletions, m.substitutions, m.swaps,
    );
}

start/end are byte offsets into the haystack, and text is the matched slice.

Next steps

• Understand the edit model and scoring.
• Learn the builder options.
• For find-and-replace, jump to Replacement.