Flex/Bison Segment Fault?

I am trying to test the code in the book "Lex & Yacc, 2nd", however,
it didn't work as described. Pls.

# uname -a
Linux redhat9 2.4.20-8 #1 Thu Mar 13 17:54:28 EST 2003 i686 i686 i386
GNU/Linux

# flex -V
flex version 2.5.4

# bison -V
bison (GNU Bison) 1.35

# flex -olexa.yy.c ch1-05.l
# bison -obisa.tab.c ch1-05.y
# gcc -o ex bisa.tab.c lexa.yy.c -ll

# ./ex
Segmentation fault