LL Grammars with e-rules: Introduction
Simplification of this part:
A
X1
X2
Xn
…
Rule r: A ® X1X2...Xn
a
 x
S
 y
Why e-rules?
•elimination of the left recursion introduces e-rule
•e-rules often make the language specification clearer
Assume that every input string of tokens ends with $.
Note: $ acts as an end marker.
Main problem with e-rules:
e
e
…
e
Maybe: a Ï First(A):
14/57
Note: We must define other sets: Empty, Follow and Predict.