/**
 * The order and the group heads of a Japanese back-of-book index (#425).
 *
 * A Japanese index files its entries in gojūon order (五十音順) by their
 * reading (読み), never by the characters written: 東京 files where とうきょう
 * does. No algorithm reads kanji reliably, so the reading comes from the
 * author (`:index[東京]{yomi="とうきょう"}`, or the ruby of the marked text);
 * an entry without one is reported (`indexReadingMissing`) and files after
 * the kana, by code point.
 *
 * The comparison is JIS X 4061 (日本語文字列照合順番), written out here so
 * that the order does not depend on the ICU data of the browser:
 *
 * - Character groups: symbols (space first) < Arabic digits < Latin < kana
 *   < kanji < geta 〓. Digit runs compare as numbers.
 * - Kana compare first on their base letter in gojūon order (あいうえお … わ
 *   ゐゑをん): katakana as hiragana, a small kana as its large form, a voiced
 *   or semi-voiced one as its plain form (ガ = か, ぱ = は, ぁ = あ). The long
 *   vowel mark ー stands for the vowel of the kana before it (カー = かあ);
 *   the iteration marks ゝゞヽヾ for the kana before them (いすゞ = いすず).
 * - Ties between equal base letters break, in this order: 清音 < 濁音 <
 *   半濁音 (は < ば < ぱ); 長音記号 < 小文字 < 繰返し記号 < 大文字 (ー < ぁ <
 *   ゝ < あ); 平仮名 < 片仮名. Last, the code points of the key.
 *
 * Kanji compare by code point: JIS X 4061 orders them by their JIS X 0208
 * code (level 1 by reading, level 2 by radical), a table the engine does
 * not ship, and an entry that reaches this comparison lacks a reading
 * anyway.
 *
 * The heads (ja typography §13): `gojuon` files an entry under the row of
 * its first kana (あ行 か行 さ行 た行 な行 は行 ま行 や行 ら行 わ行; ん under
 * わ行), the form technical and reference books use, which also says the
 * group spans a row; `kana` under the first kana itself (か for が, カ and
 * ヵ), the form of dictionaries and long name indexes.
 */
/** The base letters in gojūon order: the primary weight of a kana is its
 *  place here. */
export declare const GOJUON = "\u3042\u3044\u3046\u3048\u304A\u304B\u304D\u304F\u3051\u3053\u3055\u3057\u3059\u305B\u305D\u305F\u3061\u3064\u3066\u3068\u306A\u306B\u306C\u306D\u306E\u306F\u3072\u3075\u3078\u307B\u307E\u307F\u3080\u3081\u3082\u3084\u3086\u3088\u3089\u308A\u308B\u308C\u308D\u308F\u3090\u3091\u3092\u3093";
/** The rows of the gojūon table and where each starts in {@link GOJUON}:
 *  や and わ hold fewer letters (やゆよ; わゐゑをん, ん filed with わ). */
export declare const GOJUON_ROWS: readonly {
    head: string;
    start: number;
}[];
/** JIS X 4061 order of two index keys (readings): negative when `a` files
 *  first. See the module header. */
export declare function compareJapanese(a: string, b: string): number;
/** Whether a key's primary weights equal (the base comparison: か = が =
 *  カ = ヵ). */
export declare function sameJapaneseBase(a: string, b: string): boolean;
/** What a key files under in a Japanese index: the gojūon place of its
 *  first kana, or the group of its first character. */
export type JapaneseLead = {
    kind: 'kana';
    base: number;
} | {
    kind: 'latin' | 'digit' | 'symbol' | 'kanji';
};
/** The first collation element of `key`, as a {@link JapaneseLead}. A
 *  leading ー or iteration mark repeats nothing: it is a symbol. */
export declare function japaneseLead(key: string): JapaneseLead;
/** The row (0 = あ行 … 9 = わ行) of the base letter at `base` in
 *  {@link GOJUON}. */
export declare function gojuonRow(base: number): number;
/** The head of gojūon row `row`: あ行 … わ行. */
export declare function gojuonRowLabel(row: number): string;
/** The head of the kana group at `base`: the plain hiragana letter (か
 *  for が, カ and ヵ). */
export declare function kanaLabel(base: number): string;
/** Whether `text` holds a kanji (a Han character, 々 included): such a
 *  key needs a reading. */
export declare function hasKanji(text: string): boolean;
/** Whether `reading` is written in kana alone (see {@link KANA_READING}). */
export declare function isKanaReading(reading: string): boolean;
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