252 lines
8.3 KiB
Go
252 lines
8.3 KiB
Go
package yomichan
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import (
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"strings"
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"golang.org/x/exp/slices"
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)
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// Returns text with all katakana characters converted into hiragana.
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func katakanaToHiragana(text string) string {
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f := func(x rune) rune {
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if x >= 'ァ' && x <= 'ヶ' || x >= 'ヽ' && x <= 'ヾ' {
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return x - 0x60
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} else {
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return x
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}
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}
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return strings.Map(f, text)
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}
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// Replace hiragana iteration marks with the appropriate characters.
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// E.g. "さゝき" -> "ささき"; "たゞの" -> "ただの"
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func replaceIterationMarks(text string) string {
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iterationMarks := []struct {
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char rune
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offset rune
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}{
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{'ゝ', 0x00},
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{'ゞ', 0x01},
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}
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for _, x := range iterationMarks {
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for strings.IndexRune(text, x.char) > 0 {
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runes := []rune(text)
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idx := slices.Index(runes, x.char)
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runes[idx] = runes[idx-1] + x.offset
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text = string(runes)
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}
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}
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return text
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}
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// Returns an array of the input text split into segments.
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// E.g. "しょくぎょう" -> ["しょ", "く", "ぎょ", "う"]
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// Returns nil if no segmentation is possible.
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func makeKanaSegments(kana string) (segments []string) {
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hiragana := replaceIterationMarks(katakanaToHiragana(kana))
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kanaRunes := []rune(hiragana)
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kanaRuneCount := len(kanaRunes)
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for i := 0; i < kanaRuneCount; i++ {
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for j := 0; j < kanaRuneCount-i; j++ {
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segment := string(kanaRunes[i : kanaRuneCount-j])
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if _, ok := kanaSegmentToRomajiList[segment]; ok {
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segments = append(segments, segment)
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i = kanaRuneCount - j - 1
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break
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}
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if j == kanaRuneCount-i-1 {
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return nil
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}
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}
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}
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return segments
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}
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// Returns a map of ltr substrings of the input text.
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// E.g. "nihon" -> ["n", "ni", "nih", "niho", "nihon"]
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func makeSubstringMap(text string) map[string]bool {
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substrings := make(map[string]bool)
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for i := 1; i <= len(text); i++ {
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substring := text[:i]
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substrings[substring] = true
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}
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return substrings
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}
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// Determines if the input text is a valid romaji representation of
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// the input kana.
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//
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// The strategy is to calculate every possible romaji representation
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// of a given string of kana and check if the input text is one of
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// them. Since the number of combinations grows very large for long
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// strings of kana, we need to prune invalid branches from the
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// combination tree along the way.
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func isTransliteration(text string, kana string) bool {
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romaji := strings.TrimSpace(strings.ToLower(text))
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validSubstrings := makeSubstringMap(romaji)
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kanaSegments := makeKanaSegments(kana)
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possibilities := []string{""}
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for _, segment := range kanaSegments {
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newPossibilities := map[string]bool{}
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for _, x := range possibilities {
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for _, y := range kanaSegmentToRomajiList[segment] {
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z := x + y
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newPossibilities[z] = true
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}
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}
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possibilities = nil
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for z := range newPossibilities {
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if validSubstrings[z] {
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possibilities = append(possibilities, z)
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}
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}
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if possibilities == nil {
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return false
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}
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}
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return slices.Contains(possibilities, romaji)
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}
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var kanaSegmentToRomajiList = map[string][]string{
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"ぁ": []string{"", "a"},
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"ぃ": []string{"", "i"},
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"ぅ": []string{"", "u"},
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"ぇ": []string{"", "e"},
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"ぉ": []string{"", "o"},
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"ゃ": []string{"ya"},
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"ゅ": []string{"yu"},
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"ょ": []string{"yo"},
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"ゎ": []string{"wa"},
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"っ": []string{"", "k", "g", "s", "z", "t", "d", "f", "h", "b", "p", "n", "m", "y", "w", "c"},
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"ー": []string{"", "a", "i", "u", "e", "o", "-"},
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"あ": []string{"", "a", "ā", "wa", "wā"},
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"い": []string{"", "i", "ī", "wi", "wī"},
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"う": []string{"", "u", "ū", "wu", "wū"},
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"え": []string{"", "e", "ē", "we", "wē"},
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"お": []string{"", "o", "ō", "wo", "wō"},
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"ゔ": []string{"vu", "vū", "bu", "bū"},
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"か": []string{"ka", "kā"},
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"が": []string{"ga", "gā"},
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"き": []string{"ki", "kī"},
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"ぎ": []string{"gi", "gī"},
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"く": []string{"ku", "kū"},
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"ぐ": []string{"gu", "gū"},
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"け": []string{"ke", "kē"},
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"げ": []string{"ge", "gē"},
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"こ": []string{"ko", "kō"},
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"ご": []string{"go", "gō"},
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"さ": []string{"sa", "sā"},
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"ざ": []string{"za", "zā"},
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"し": []string{"si", "sī", "shi", "shī"},
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"じ": []string{"zi", "zī", "ji", "jī"},
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"す": []string{"su", "sū"},
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"ず": []string{"zu", "zū"},
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"せ": []string{"se", "sē"},
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"ぜ": []string{"ze", "zē"},
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"そ": []string{"so", "sō"},
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"ぞ": []string{"zo", "zō"},
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"た": []string{"ta", "tā"},
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"だ": []string{"da", "dā"},
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"ち": []string{"ti", "tī", "chi", "chī"},
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"ぢ": []string{"di", "dī", "dhi", "dhī", "ji", "jī", "dji", "djī", "dzi", "dzī"},
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"つ": []string{"tu", "tū", "tsu", "tsū"},
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"づ": []string{"du", "dū", "dzu", "dzū", "zu", "zū"},
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"て": []string{"te", "tē"},
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"で": []string{"de", "dē"},
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"と": []string{"to", "tō"},
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"ど": []string{"do", "dō"},
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"な": []string{"na", "nā"},
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"に": []string{"ni", "nī"},
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"ぬ": []string{"nu", "nū"},
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"ね": []string{"ne", "nē"},
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"の": []string{"no", "nō"},
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"は": []string{"ha", "hā", "wa", "wā", "a", "ā"},
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"ば": []string{"ba", "bā"},
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"ぱ": []string{"pa", "pā"},
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"ひ": []string{"hi", "hī", "i", "ī"},
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"び": []string{"bi", "bī"},
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"ぴ": []string{"pi", "pī"},
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"ふ": []string{"hu", "hū", "fu", "fū", "u", "ū"},
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"ぶ": []string{"bu", "bū"},
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"ぷ": []string{"pu", "pū"},
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"へ": []string{"he", "hē", "e", "ē"},
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"べ": []string{"be", "bē"},
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"ぺ": []string{"pe", "pē"},
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"ほ": []string{"ho", "hō", "o", "ō"},
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"ぼ": []string{"bo", "bō"},
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"ぽ": []string{"po", "pō"},
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"ま": []string{"ma", "mā"},
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"み": []string{"mi", "mī"},
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"む": []string{"mu", "mū"},
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"め": []string{"me", "mē"},
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"も": []string{"mo", "mō"},
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"や": []string{"ya", "yā"},
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"ゆ": []string{"yu", "yū"},
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"よ": []string{"yo", "yō"},
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"ら": []string{"ra", "rā"},
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"り": []string{"ri", "rī"},
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"る": []string{"ru", "rū"},
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"れ": []string{"re", "rē"},
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"ろ": []string{"ro", "rō"},
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"わ": []string{"wa", "wā"},
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"ゐ": []string{"wi", "wī", "i", "ī"},
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"ゑ": []string{"we", "wē", "e", "ē"},
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"を": []string{"wo", "wō", "o", "ō"},
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"ん": []string{"n", "n'", "m"},
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"うぁ": []string{"wa", "wā", "ua", "uā"},
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"うぃ": []string{"wi", "wī", "ui", "uī"},
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"うぇ": []string{"we", "wē", "ue", "uē"},
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"うぉ": []string{"wo", "wō", "uo", "uō"},
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"きゃ": []string{"kya", "kyā"},
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"きゅ": []string{"kyu", "kyū"},
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"きょ": []string{"kyo", "kyō"},
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"ぎゃ": []string{"gya", "gyā"},
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"ぎゅ": []string{"gyu", "gyū"},
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"ぎょ": []string{"gyo", "gyō"},
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"くゎ": []string{"kwa", "kwā"},
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"くゅ": []string{"kyu", "kyū"},
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"しぇ": []string{"she", "shē", "shie", "shiē"},
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"しゃ": []string{"sha", "shā", "sya", "syā"},
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"しゅ": []string{"shu", "shū", "syu", "syū"},
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"しょ": []string{"sho", "shō", "syo", "syō"},
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"じぇ": []string{"je", "jē"},
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"じゃ": []string{"ja", "jā", "jya", "jyā"},
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"じゅ": []string{"ju", "jū", "jyu", "jyū"},
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"じょ": []string{"jo", "jō", "jyo", "jyō"},
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"ちぁ": []string{"cha", "chā", "chia", "chiā"},
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"ちぇ": []string{"che", "chē", "chie", "chiē"},
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"ちゃ": []string{"cha", "chā", "tya", "tyā"},
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"ちゅ": []string{"chu", "chū", "tyu", "tyū"},
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"ちょ": []string{"cho", "chō", "tyo", "tyō"},
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"ぢゃ": []string{"ja", "jā", "jya", "jyā", "dya", "dyā"},
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"ぢゅ": []string{"ju", "jū", "jyu", "jyū", "dyu", "dyū"},
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"ぢょ": []string{"jo", "jō", "jyo", "jyō", "dyo", "dyō"},
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"つぁ": []string{"tsa", "tsā", "tsua", "tsuā"},
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"つぇ": []string{"tse", "tsē", "tsue", "tsuē"},
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"てぃ": []string{"ti", "tī", "tei", "teī"},
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"でぃ": []string{"di", "dī", "dei", "deī"},
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"でゅ": []string{"dyu", "dyū", "deyu", "deyū"},
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"にゃ": []string{"nya", "nyā"},
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"にゅ": []string{"nyu", "nyū"},
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"にょ": []string{"nyo", "nyō"},
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"ひゃ": []string{"hya", "hyā"},
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"ひゅ": []string{"hyu", "hyū"},
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"ひょ": []string{"hyo", "hyō"},
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"びゃ": []string{"bya", "byā"},
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"びゅ": []string{"byu", "byū"},
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"びょ": []string{"byo", "byō"},
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"ぴゃ": []string{"pya", "pyā"},
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"ぴゅ": []string{"pyu", "pyū"},
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"ぴょ": []string{"pyo", "pyō"},
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"ふぁ": []string{"fa", "fā"},
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"ふぃ": []string{"fi", "fī"},
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"ふぇ": []string{"fe", "fē"},
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"ふぉ": []string{"fo", "fō"},
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"みゃ": []string{"mya", "myā"},
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"みゅ": []string{"myu", "myū"},
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"みょ": []string{"myo", "myō"},
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"りゃ": []string{"rya", "ryā"},
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"りゅ": []string{"ryu", "ryū"},
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"りょ": []string{"ryo", "ryō"},
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}
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