I have the next grammar:
C := (PZ)
P := X | C
X := iQ | eQ | rQ
Q := AX | ε
A := +
L := >
Z := LP | AP | ε
and i am using JFLAP to build an LL(1) parsing table, but at the moment that i type those rules, JFLAP throws me an error that says: the grammar is not LL(1).I have found where the mistake is, in the rule 'Q'.
The first set of Q is Q = {+,ε}, and the follow set of Q is Q = { ), + , >} and in the parsing table i am going to have two rules in table[Q,+] and that´s the mistake, but i dont know how to fix it because i need to have the rule Q -> ε
The basic problem is that your grammar is ambiguous -- you have two nested repeating patterns from your rules for X
and Z
and both of them can match an i+i
fragment. So you need to decide how you want to resolve that ambiguity -- which way should a fragment like i+i
match:
PZ PZ
/ \ / \
X ε X AP
/ \ / \ / \
i Q i Q + X
/ \ / / \
A X ε i Q
/ / \ |
+ i Q ε
|
ε
The easiest fix is to make it always match the right example, which you can do by just getting rid of the X
/ Q
repeating pattern:
C := (PZ)
P := X | C
X := i | e | r
A := +
L := >
Z := LP | AP | ε
If you want to always match the left example, you need to disallow +
in the Z
pattern:
C := (PZ)
P := X | C
X := iQ | eQ | rQ
Q := AX | ε
A := +
L := >
Z := LP | ε
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