##### Exceptions

    def __init__(self, cause):

        exc.ExceptionWithCause.__init__(self, 'Invalid XML function syntax',

            cause)

##### Functions

    try:

        cond = items['cond']

        then = items['then']

    else_ = items.get('else', None)

    cond = bool(cast(strings.ustr, cond))

    if cond: return then

    try:

        label = items['label']

        value = items['value']

    return label+': '+value

funcs['_label'] = _label

def _nullIf(items):

    items = dict(conv_items(strings.ustr, items))

    try: null = items['null']

    value = items.get('value', None)

    type_str = items.get('type', None)

    try: type_ = types_by_name[type_str]

    null = type_(null)

    try: return util.none_if(value, null)

            if re.match(r'^\w+$', repl):

                repl = r'(?<![^\W_])'+repl+r'(?![^\W_])' # match whole word

            value = re.sub(repl, with_, value)

    return util.none_if(value, u'') # empty strings always mean None

funcs['_replace'] = _replace

            elif action == 'to':

                try: quantity = units.convert(quantity, units_)

                except ValueError, e: raise FormatException(e)

    except units.MissingUnitsException, e: raise FormatException(e)

    return units.quantity2str(quantity)

funcs['_units'] = _units

    out_items = []

    for part, value in items:

        try: slice_ = name_parts_slices[part]

        out_items.append((part, ' '.join(value.split(' ')[slice_])))

    return _name(out_items)

funcs['_namePart'] = _namePart

        next = cast(strings.ustr, items['next'])

        require = cast(strings.ustr, items['require'])

        root = items['path']

    node = root

    while node != None: