encode static method

String encode(String s)

Encodes this string using Soundex (first letter + 3 digits).

Non-alpha characters are ignored. Returns 4-char string (letter + 3 digits), or empty string if no letters.

Example:

SoundexUtils.encode('Robert');  // 'R163'
SoundexUtils.encode('Rupert');   // 'R163'

Audited: 2026-06-12 11:26 EDT

Implementation

static String encode(String s) {
  if (s.isEmpty) return '';
  final String letters = s.toUpperCase().replaceAll(RegExp(r'[^A-Z]'), '');
  if (letters.isEmpty) return '';
  final StringBuffer out = StringBuffer(letters[0]);
  int prev = _code(letters[0]);
  int count = 1;
  for (int i = 1; i < letters.length && count < _soundexCodeLength; i++) {
    final String ch = letters[i];
    final int c = _code(ch);
    if (c != 0) {
      // Only emit a new digit when it differs from the previous coded letter
      // (adjacent same-code letters collapse), but always remember it.
      if (c != prev) {
        out.write(c);
        count++;
      }
      prev = c;
    } else if (_isVowel(ch)) {
      // Vowels (A,E,I,O,U,Y) BREAK adjacency: reset prev so a following
      // consonant with the same code as the previous one is still coded
      // (e.g. 'Gauss' -> G200, not G000). H and W are transparent and must
      // NOT reset prev, so they fall through and leave it unchanged.
      prev = 0;
    }
  }
  while (count < _soundexCodeLength) {
    out.write(_zero);
    count++;
  }
  return out.toString();
}