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fsa2 - /usr/bin/env python FSA module This module...

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#!/usr/bin/env python """ FSA module This module implements simple deterministic and non-deterministic finite state automata. It follows the description in Chapter 2 of Jurafsky and Martin (2000) fairly closely. @author: Rob Malouf @organization: Dept. of Linguistics, San Diego State University @contact: [email protected] @version: 1 @since: 30-January-2008 """ class FSA(object): """ General finite-state automaton class An FSA consists of: - an alphabet (C{self.alphabet}) - a state-transition table (C{self.transition_table}) - an initial state (C{self.initial}) - a set of final states (C{self.final}) """ def __init__(self,T,finals,initial=0): """ Create a new FSA object @param T: the transition function @type T: a C{list} of C{dict}s @param finals: final states @type finals: C{list} @param initial: initial state (by default, 0) @type initial: C{int} @raise ValueError: the FSA is mis-specified somehow """ # transition function self.transition_table = T for state in self.transition_table: for symbol in state: # the value of the transition function should be a list of states if not hasattr(state[symbol],'__getitem__'): state[symbol] = [ state[symbol] ] for newState in state[symbol]: try: self.transition_table[newState] except: raise ValueError,'%s not a valid state'%newState # initial state self.initial = initial try:
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self.transition_table[self.initial] except: raise ValueError,'%s not a valid initial state'%initial # final states try: self.finals = set(finals) for final in self.finals: self.transition_table[final] except: raise ValueError,'%s not valid final states'%finals # alphabet self.alphabet = set() for state in self.transition_table:
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