"Has player RP name" script

stock RpName(playerid)
{
    new name[MAX_PLAYER_NAME],
        strokeCount,
        firstName[MAX_PLAYER_NAME],
        lastName[MAX_PLAYER_NAME],
        capCount;
    GetPlayerName(playerid, name, MAX_PLAYER_NAME);
    for (new i = 0; i < strlen(name); i++)
    {
        if (!IsLetter(name[0], true)) return false;
        if (name[i] == '[' || name[i] == ']' || name[i] >= '0' && name[i] <= '9' || name[i] == '@') return false;
        if (name[i] == '_')
        {
            strokeCount++;
            if (name[i - 1] == '_' || name[i + 1] == '_') return false;
            if (!IsLetter(name[i + 1], true)) return false;
            strmid(firstName, name, 0, i);
            strmid(lastName, name, i + 1, MAX_PLAYER_NAME);
            for (new b = 0; b < strlen(firstName); b++)
            {
                if (IsLetter(firstName[b], true))
                    capCount++;
                if (capCount > 1)
                    return false;
            }
            capCount = 0;
            for (new b = 0; b < strlen(lastName); b++)
            {
                if (IsLetter(lastName[b], true))
                    capCount++;
                if (capCount > 1)
                    return false;
            }
        }
    }
    return (strokeCount == 1);
}

//And the 'IsLetter' function:
stock IsLetter(const input, bool:capitalOnly = false, bool:lowerCaseOnly = false)
{
    if (capitalOnly)
        return (input >= 'A' && input <= 'Z');
    else if (lowerCaseOnly)
        return (input >= 'a' && input <= 'z');
    else return (input >= 'a' && input <= 'z' || input >= 'A' && input <= 'Z');
}