def _build_first_seq(self, first_set, seq):
"""Fill `first_set` with the current FIRST set of the string of
symbols `seq`. Returns True if `first_set` is changed and False
otherwise."""
change = False
for symbol in seq:
for fst in self._non_nullable_head(symbol):
if set_add_change(first_set, fst):
change = True
if not self._is_nullable(symbol):
break
else:
if set_add_change(first_set, ''):
change = True
return change
def _build_follow_seq(self, nonterminal, follow_set, seq):
"""Fill `follow_set` with the current FOLLOW set of the string of
symbols `seq`. Returns True if `follow_set` is changed and False
otherwise."""
change = False
first_seq = self.first(seq)
for symb in first_seq:
if symb == '':
continue
if set_add_change(follow_set, symb):
change = True
if '' in first_seq:
for symb in self.follow(nonterminal):
if set_add_change(follow_set, symb):
change = True
return change
