Swapping noun cardinals

In a chunk, a cardinal word, tagged as CD, refers to a number, such as 10. These cardinals often occur before or after a noun. For normalization purposes, it can be useful to always put the cardinal before the noun.

How to do it...

The swap_noun_cardinal() function is defined in transforms.py. It swaps any cardinal that occurs immediately after a noun with the noun so that the cardinal occurs immediately before the noun. It uses a helper function, tag_equals(), which is similar to tag_startswith(), but in this case, the function it returns does an equality comparison with the given tag:

def tag_equals(tag):
  def f(wt):
    return wt[1] == tag
  return f

Now we can define swap_noun_cardinal():

def swap_noun_cardinal(chunk):
  cdidx = first_chunk_index(chunk, tag_equals('CD'))
  # cdidx must be > 0 and there must be a noun immediately before it
  if not cdidx or not chunk[cdidx-1][1].startswith('NN'):
    return chunk

  noun, nntag = chunk[cdidx-1]
  chunk[cdidx-1]...