The failure function
Let Q be the set of states of an Aho/Corasick automaton.
Let h: Q -> Q + {fail} denote the failure function.
Let q, q' be states of Q.
The failure function of an Aho/Corasick automaton is defined as follows:
h(q) = q' iff among the states of Q, q' delivers the longest true suffix
of path(q)
Example