ex49:making sentences

    a=Making_sentences.Sentence(('noun','princess'),('verb','go'), ('noun','bear'))
    b=lexicon.scan("princess go to bear")
    d = b
    print b
    c=Making_sentences.parse_sentence(d)
    print b
    assert_equal(b[0][1],c.subject)

i get this:

    assert_equal(b[0][1],c.subject)
IndexError: list index out of range
-------------------- >> begin captured stdout << ---------------------
[('noun', 'princess'), ('verb', 'go'), ('stop', 'to'), ('noun', 'bear')]
[]

--------------------- >> end captured stdout << ----------------------

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