grammar4.closure, EFact closes over all factories except for EmptyFact

E	::= S | S + E
S	::= T | V | P
T	::= num | num * T
V	::= id | id * T
P	::= ( E )


E	::= S E1
E1	::= E1a | Empty
E1a	::= + E
S	::= T | V | P
T	::= num T1
V	::= id T1
T1	::= T1a | Empty
T1a	::= * T
P	::= ( E )