def computeLookaheads(self):
D = Symbol("#", self.grammar)
for kSet in self.kernelTable:
# Find the items
I = LA0.closure(kSet)
# Dictionary of symbol and kernelEntry
gotoTable = {}
for kernel in kSet:
for item in closure(Item(kernel.production, kernel.position, D)):
a = item.nextSymbol()
if a == None:
continue
if not gotoTable.has_key(a):
SearchFor = ()
for it in LA0.kernelGoto(I, a).kernels():
SearchFor += (it,)
# rSet is the KernelEntry where items == SearchFor
rSet = None
for entry in self.kernelTable:
if entry.match(SearchFor):
rSet = entry
break
assert rSet != None, "rSet must not be None!!"
gotoTable[a] = rSet
else:
rSet = gotoTable[a]
# rItem is the LA0 item where searching for...
rItem = item.toLA0()
rItem.position += 1 # Move to the other side of X
rItem.rehash()
if item.lookahead != D:
rSet.addLookahead(rItem, item.lookahead)
else:
to = rSet.idOf(rItem)
kSet.addPropagation(kernel, to)
def __init__(self, grammar):
self.grammar = grammar
self.kernelTable = () # Tuple of kernelItemSets
for itSet in LA0.items(self.grammar):
t = KernelItemSet()
for k in itSet.kernels():
t.addKernel(k)
self.kernelTable += (t,)
# Add the EOF symbol as lookahead for root production
rItem = LA0.Item(self.grammar.rootProduction, 0)
for kset in self.kernelTable:
if rItem in kset:
kset.addLookahead(rItem, self.grammar.EOF)
