Top-Down Parsing: Introduction
S
A
a
x
y
Problem:
Which rule
to use
?
Basic idea
:
Table:
...
a
...
...
...
A
t
(
p
,
a
)
a
(
A
,
a
)
a
Use rule
r
:
A
®
x
Question:
Could you construct
this table
for
any
CFG
?
Answer
:
NO
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