#text #typesetting


Knuth-Liang hyphenation for a variety of languages

3 releases

Uses old Rust 2015

0.7.4 Nov 23, 2019
0.7.3 Nov 23, 2019
0.7.2 Nov 23, 2019

#162 in Text processing

25 downloads per month
Used in spandex


758 lines


Hyphenation for UTF-8 strings in a variety of languages.

hyphenation = "0.7.1"

Two strategies are available:





The hyphenation library relies on hyphenation dictionaries, external files that must be loaded into memory. To start with, however, it can be more convenient to embed them in the compiled artifact.

hyphenation = { version = "0.7.1", features = ["embed_all"] }

The topmost module of hyphenation offers a small prelude that can be imported to expose the most common functionality.

use hyphenation::*;

// Retrieve the embedded American English dictionary for `Standard` hyphenation.
let en_us = Standard::from_embedded(Language::EnglishUS) ?;

// Identify valid breaks in the given word.
let hyphenated = en_us.hyphenate("hyphenation");

// Word breaks are represented as byte indices into the string.
let break_indices = &hyphenated.breaks;
assert_eq!(break_indices, &[2, 6]);

// The segments of a hyphenated word can be iterated over.
let segments = hyphenated.into_iter();
let collected : Vec<String> = segments.collect();
assert_eq!(collected, vec!["hy", "phen", "ation"]);

/// `hyphenate()` is case-insensitive.
let uppercase : Vec<_> = en_us.hyphenate("CAPITAL").into_iter().collect();
assert_eq!(uppercase, vec!["CAP", "I", "TAL"]);

Loading dictionaries at runtime

The current set of available dictionaries amounts to ~7MB of data, the embedding of which is seldom desirable. Most applications should prefer to load individual dictionaries at runtime, like so:

let path_to_dict = "/path/to/en-us.bincode";
let english_us = Standard::from_path(Language::EnglishUS, path_to_dict) ?;

Dictionaries bundled with hyphenation can be retrieved from the build folder under target, and packaged with the final application as desired.

$ find target -name "dictionaries"


Dictionaries can be used in conjunction with text segmentation to hyphenate words within a text run. This short example uses the unicode-segmentation crate for untailored Unicode segmentation.

use unicode_segmentation::UnicodeSegmentation;

let hyphenate_text = |text : &str| -> String {
    // Split the text on word boundaries—
        // —and hyphenate each word individually.
        .flat_map(|word| en_us.hyphenate(word).into_iter())

let excerpt = "I know noble accents / And lucid, inescapable rhythms; […]";
assert_eq!("I know no-ble ac-cents / And lu-cid, in-escapable rhythms; […]"
          , hyphenate_text(excerpt));


Hyphenation patterns for languages affected by normalization occasionally cover multiple forms, at the discretion of their authors, but most often they don’t. If you require hyphenation to operate strictly on strings in a known normalization form, as described by the Unicode Standard Annex #15 and provided by the unicode-normalization crate, you may specify it in your Cargo manifest, like so:

version = "0.7.1"
features = ["nfc"]

The features field may contain exactly one of the following normalization options:

  • "nfc", for canonical composition;
  • "nfd", for canonical decomposition;
  • "nfkc", for compatibility composition;
  • "nfkd", for compatibility decomposition.

It is recommended to build hyphenation in release mode if normalization is enabled, since the bundled hyphenation patterns will need to be reprocessed into dictionaries.


hyphenation © 2016 tapeinosyne, dual-licensed under the terms of either:

  • the Apache License, Version 2.0
  • the MIT license

texhyphen and other hyphenation patterns © their respective owners; see patterns/*.lic.txt files for licensing information.