SoundEx

This document implements the [SoundEx] algorithm.

This algorithm is often used to index names.

SoundEx

/**
    Returns the score of an character
*/
static function byte SoundExScore(int c)
{
    switch (c)
    {
        case 68: /* B */ case 70: /* F */ case 80: /* P */ case 86: /* V */
            return 1;
        case 67: /* C */ case 71: /* G */ case 74: /* J */ case 75: /* K */
        case 81: /* Q */ case 83: /* S */ case 88: /* X */ case 90: /* Z */
            return 2;
        case 68: /* D */ case 84: /* T */
            return 3;
        case 76: // L
            return 4;
        case 77: /* M */ case 78: /* N */
            return 5;
        case 82: // R
            return 6;
    }
    /* Disregard the letters A, E, I, O, U, H, W, and Y. */
    return 0;
}

/**
    Returns the SoundEx value of a string, size defaults to 4
*/
static function string SoundEx(coerce string in, optional byte size)
{
    local string res;
    local int i;
    local byte cs, ls; // cs = current score; ls = previous score

    if (size == 0) size = 4;
    res = "";
    if (in != "")
    {
        in = Caps(in); // upper case all
        // always use first char
        res = Left(in, 1);
        ls = SoundExScore(asc(res));
        for (i = 0; i < len(in); i++)
        {
            cs = SoundExScore(asc(Mid(in, i, 1)));
            if ((cs > 0) && (cs != ls))
            {
                ls = cs;
                res $= string(cs);
            }
            if (len(res) == size) break;
        }
    }
    while (len(res) < size) res $= "0";
    return res;
}

Related Topics

• DoubleMetaPhone

Category Algorithm