#information-retrieval #dictionary #retrieval #map #search #information

no-std fst-no-std

Use finite state transducers to compactly represents sets or maps of many strings (> 1 billion is possible)

2 releases

0.4.8 Jan 18, 2024
0.4.7 Jan 18, 2024

#255 in Algorithms

33 downloads per month



fst no-std mode

This is a fork of fst adding support for no_std targets (see no_std usage for details).

If you're unsure whether to use this fork or the original one: Just use the original, chances are that's more up-to-date.




Simply add a corresponding entry to your Cargo.toml dependency list:

fst-no-std = "0.4"


This example demonstrates building a set in memory and executing a fuzzy query against it. You'll need fst_no_std = "0.4" with the levenshtein feature enabled in your Cargo.toml.

use fst_no_std::{IntoStreamer, Set};
use fst_no_std::automaton::Levenshtein;

fn main() -> Result<(), Box<dyn std::error::Error>> {
  // A convenient way to create sets in memory.
  let keys = vec!["fa", "fo", "fob", "focus", "foo", "food", "foul"];
  let set = Set::from_iter(keys)?;

  // Build our fuzzy query.
  let lev = Levenshtein::new("foo", 1)?;

  // Apply our fuzzy query to the set we built.
  let stream = set.search(lev).into_stream();

  let keys = stream.into_strs()?;
  assert_eq!(keys, vec!["fo", "fob", "foo", "food"]);

Check out the documentation for a lot more examples!

Cargo features

  • std - Enabled by default. Adds features that depend on the standard library.
  • alloc - Enabled by default. Adds features that depend on alloc.
  • levenshtein - Disabled by default. This adds the Levenshtein automaton to the automaton sub-module. This includes an additional dependency on utf8-ranges and std.

no_std Usage

You can use this crate in no_std environments by disabling default features, like so:

fst-no-std = { version = "0.4", default-features = false }

This way fst-no-std will not depend on the standard library and not even allocate (!) at the cost of being rather kneecaped: You can not construct FSTs and the evailable querying features are limited to simple lookups. You can optionally enable the alloc feature which adds a dependency on the alloc crate (i.e. you will need a global allocator) but it enables all querying features.


Licensed under the MIT license.