docs: def vi_pos_matching (line, index=0):
      '''find matching <([{}])>'''
      anchor = None
      target = None
      delta = 1
      count = 0
      try:
          while 1:
              if anchor is None:
                  # first find anchor
                  try:
                      target, delta = _vi_dct_matching [line [index]]
                      anchor = line [index]
                      count = 1
                  except KeyError:
                      index += 1
                      continue
              else:
                  # Here the anchor has been found
                  # Need to get corresponding target
                  if index < 0:
                      return -1
                  if line [index] == anchor:
                      count += 1
                  elif line [index] == target:
                      count -= 1
                      if count == 0:
                          return index
              index += delta
      except IndexError:
          return -1