First(X) for Gexpr3: Example
F ® i Î P: add First(i) = {i} to First(F)
F ® (E) Î P: add First(() = {(} to First(F)
Summary: First(F) = {i, (}
T’ ® *FT’ Î P: add First (*) = {*} to First(T’)
Summary: First(T’) = {*}
T ® FT’ Î P: add First (F) = {i, (} to First(T)
Summary: First(T) = {i, (}
E’ ® +TE’ Î P: add First (+) = {+} to First(E’)
Summary: First(E’) = {+}
E ® TE’ Î P: add First (T) = {i, (} to First(E)
Summary: First(E) = {i, (}
22/57
First( i ) := {i}
First( + ) := {+}
First( * ) := {*}
First( ( ) := { ( }
First( ) ) := { ) }
Initialization:
First(E) :=  Æ
First(E’) :=  Æ
First(T) :=  Æ
First(T’) :=  Æ
First(F) :=  Æ
• No First set can be changed.