def next_lookup(self, symbol):
"""Returns the next TerminalSymbols produced by the input symbol within this grammar definition"""
result = []
if symbol == self.initialsymbol:
result.append(EndSymbol())
for production in self.productions:
if symbol in production.rightside:
nextindex = production.rightside.index(symbol) + 1
while nextindex < len(production.rightside):
nextsymbol = production.rightside[nextindex]
firstlist = self.first_lookup(nextsymbol)
cleanfirstlist = Choice(
[x for x in firstlist if x != NullSymbol()])
result.append(cleanfirstlist)
if NullSymbol() not in firstlist:
break
else:
result += self.next_lookup(
production.leftside[0]
) #reached the end of the rightside
return result
def test_simple(self):
alphabet = Choice([String('a')])
base = Choice([String('a')])
graph = graph_from_alphabet(alphabet, base)
self.assertEqual(len(graph.node), 2)