X-ian, in Python.

x_ian.py

# Given a string x, returns True iff all the letters in x
# are contained in word in the same order as they appear in x.
# An exercise from MITx: 6.00.1x Introduction to Computer Science and Programming Using Python.

def x_ian(x, word):
  """
  Given a string x, returns True iff all the letters in x are
  contained in word in the same order as they appear in x.

  >>> x_ian('eric', 'meritocracy')
  True
  >>> x_ian('eric', 'cerium')
  False
  >>> x_ian('john', 'mahjong')
  False
    
  x: a string
  word: a string
  returns: True if word is x_ian, False otherwise
  """
  if not word:
    return False
  elif not x or len(x) == 0:
    return True
  elif len(x) == 1:
    return x in word
  else:
    x_pos = word.find(x[0])
    if x_pos > -1:
      return x_ian(x[1:], word[(x_pos + 1):])
    else:
      return False