created_at2016-02-17 00:45:32.366426
updated_at2021-08-19 10:23:20.719344
descriptionKnuth-Liang hyphenation for a variety of languages
owners (github:zcashfoundation:owners)





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

hyphenation = "0.8.3"

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 = "0.8.3", 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` Knuth-Liang 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, 7]);

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

let unmarked = hyphenated.iter().segments();
let collected : Vec<&str> = unmarked.collect();
assert_eq!(collected, vec!["hy", "phen", "a", "tion"]);

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

Loading dictionaries at runtime

The current set of available dictionaries amounts to ~2.8MB of data. Although embedding them is an option, 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 = "0.8.3"
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.

You may prefer 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

hyph-utf8 hyphenation patterns © their respective owners; see their master files for licensing information.

patterns/hyph-hu.ext.txt (extended Hungarian hyphenation patterns) is licensed under:

  • MPL 1.1 (refer to patterns/hyph-hu.ext.lic.txt)

patterns/hyph-ca.ext.txt (extended Catalan hyphenation patterns) is licensed under:

  • LGPL v.3.0 or higher (refer to patterns/hyph-ca.ext.lic.txt)
Commit count: 188

cargo fmt