Given a character c t+1 and a hypothesis h t , h t+1 can be generated in two ways, by either appending c t+1 to BU F t (t = n), or first moving the sequence in BU F t into SEG t as a new word, and then appending c t+1 to BU F t (t = n).
in the former case: in the latter case: when generating the hypothesis for c n+1 (the end of sentence marker), the sequence in BU F n has to be moved into SEG n , and c n+1 also needs to be moved into SEG n as a new word.