def parse_range(str_, range_sep='-'):

    default = (str_, None)

    start, sep, end = str_.partition(range_sep)

    if sep == '': return default # not a range

    return tuple(d.strip() for d in (start, end))

def _rangeStart(items):

    items = dict(conv_items(str, items))

    try: value = items['value']

    except KeyError, e: raise SyntaxException(e)

    return parse_range(value)[0]

funcs['_rangeStart'] = _rangeStart

def _rangeEnd(items):

    items = dict(conv_items(str, items))

    try: value = items['value']

    except KeyError, e: raise SyntaxException(e)

    return parse_range(value)[1]

funcs['_rangeEnd'] = _rangeEnd