'Construct a new ``ChunkRule``.
:type tag_pattern: str
:param tag_pattern: This rule\'s tag pattern.  When
applied to a ``ChunkString``, this rule will
chunk any substring that matches this tag pattern and that
is not already part of a chunk.
:type descr: str
:param descr: A short description of the purpose and/or effect
of this rule.'

def __init__(self, tag_pattern, descr):

    self._pattern = tag_pattern
    regexp = re.compile((u'(?P<chunk>%s)%s' % (tag_pattern2re_pattern(tag_pattern), ChunkString.IN_CHINK_PATTERN)))
    RegexpChunkRule.__init__(self, regexp, u'{\\g<chunk>}', descr)
