Fuzzies

Fuzzies is a fast, friendly integration layer that bridges the gap between low-level finite state transducers (fst) and Levenshtein automata, saving you from writing tedious boilerplate.

More information about this crate can be found in the crate documentation

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Installation

cargo add fuzzies

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Example

use fuzzies::{Dictionary, DictionaryError};

fn main() -> Result<(), DictionaryError> {
    // Prepare your raw text file (must be sorted lexicographically)
    // Fuzzies provides a handy in-place sorter for convenience:
    Dictionary::sort("words.txt")?;

    // Build the immutable binary FST from the sorted text file
    Dictionary::build("words.txt", "words.fst")?;

    // Load the dictionary (memory-mapped from disk)
    let dict = Dictionary::open("words.fst")?;

    // Check for exact matches instantly
    if dict.contains("banana") {
        println!("Exact match found!");
    }

    // Perform a fuzzy search with a max typo distance of 2 and limit of 5 results
    let results = dict.search("banaan")
        .distance(2)
        .transposition(true) // Handles adjacent swaps (e.g., "teh" -> "the")
        .prefix(false)       // Set to true for prefix fuzzy lookups
        // .ge("a").lt("e")  // Optionally restrict search bounds (e.g., 'a' <= key < 'e')
        .limit(5)
        .execute()?;
    
    for result in results {
        println!("Found: {}", result);
    }

    // Batch search (multithreaded, defaults to a distance of 1)
    let queries = vec!["aple", "baxana", "cherri"];
    let batch_results = dict.batch_search(&queries).execute();

    for (query, result) in queries.iter().zip(batch_results) {
        match result {
            Ok(matches) => println!("Query '{}' found {} matches", query, matches.len()),
            Err(e) => eprintln!("Error searching for '{}': {}", query, e),
        }
    }

    Ok(())
}

Embedding Data

If you don't want to manage external .fst files on disk, embed the dataset directly into your application:

static DICT_DATA: &[u8] = include_bytes!("../assets/words.fst");
let dict = Dictionary::from_embedded(DICT_DATA)?;

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Built with Fuzzies

Check out real-world projects utilizing fuzzies:

• Mamoru: A blazing-fast Git commit-msg hook that embeds a compiled dictionary of over 106,000 words to instantly catch and block typos before they make it into your version control history.

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🎈 Performance

The following benchmarks were gathered using Criterion on an Intel Core i5-10300H (4 cores / 8 threads). You can re-run these on your hardware with cargo bench.

Note

Running cargo bench on the published crate executes against a small, dynamically generated dataset. The 106,000-word benchmarks shown below were gathered independently using a local dictionary.

Operation	1,000 Entries	106,000 Entries	Scaling Factor
contains (Hit)	34.60 ns	65.00 ns	~1.8x
contains (Miss)	11.08 ns	100.06 ns	~9.0x
Exact Search (dist = 0)	2.18 µs	4.48 µs	~2.0x
Fuzzy Search (dist = 1)	7.97 µs	61.58 µs	~7.7x
Prefix Search	5.53 µs	125.36 µs	Result-size bound
Range Search ('b'..='c')	4.35 µs	626.37 µs	Result-size bound
Batch (1,000 queries)	4.02 ms (4.0 µs/q)	14.88 ms (14.8 µs/q)	~3.7x

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License

This project is licensed under the MIT license.