This document discusses the process of using lex and yacc to build a compiler. It provides examples of: 1. Defining lex and yacc rules to recognize simple input patterns like numbers and operators. 2. Compiling the lex and yacc files and resolving conflicts in the yacc parsing rules. 3. Testing the compiler on sample inputs and outputting the results.

1. - $-
ý

2. .è
F
$
S
.

3. S .
●
S
– . .
. .
–
●
ID
–
–
S

4. .
●
– . . ..... .
– .
●
(CFG)
–
●
(LR )
–8 .
(LL )
–9 .

5. .
●
– _ .è
●
.è
● .
● _

6. S
.
S
(1/3)
●
S
– ... .
● lex.flex.jflex (etc...)
– . . ......
!

7. S
.
S
(2/3)
lex!.
●
1.:^,!!!!!!|!qsjoug)#OVNCFSquot;quot;]o#*!~
!]u]o^,!!!!|!0+!ep!opuijoh!+0!~
/,!!!!!!!!!!|!qsjoug)#PUIFSquot;quot;]o#*!~
jou!nbjo)*!|
!!!!xijmf)zzmfy)*!quot;!1*!|
!!!!~
!!!!sfuvso!1
~

8. S
.
S
(3/3)
●
%!gmfy!mfy2/m
%!hdd!mfy/zz/d!.mgm
%!/0b/pvu
4
OVNCFSquot;quot;
54
OVNCFSquot;quot;
iphf
PUIFSquot;quot;

9. .
(1/4)
●
– ... .
● yacc.bison.CUP.JavaCC.racc (etc...)
–
S
. . . .
è

10. .
(2/4)
yacc!.
●
uplfo!OVNCFS
uplfo!QMVT
T!!!!!!!;!F!|!qsjoug)#sftvmu!;!e]o#-!%2*!~
!!!!!!!!
F!!!!!!!;!F!QMVT!F!|!%%!!%2!,!%4!~
!!!!!!!!}!OVNCFS!|!%%!!%2!~
!!!!!!!!
$jodmvef!#mfy/zz/d#
jou!nbjo)*!|
!!!!zzqbstf)*
~

11. .
(3/4)
lex!.
●
#,#!!!!!|!sfuvso!QMVT!~
]u]o!^!|!0+!ep!opuijoh!+0!~
1.:^,!!|
!!!!!!!!ttdbog)zzufyu-!#e#-!'zzmwbm*
!!!!!!!!sfuvso!OVNCFS
~
/!!!!!!!|
!!!!!!!!qsjoug)#cbe!joqvu!dibsbdufsquot;quot;]o#*
!!!!!!!!qsjoug)#jhopsfequot;quot;]o#*
~

12. .
(4/4)
●
%!gmfy!zbdd3/m
%!cjtpo!zbdd3/z
zbdd3/z;!dpogmjdut;!2!tijgu0sfevdf
%!hdd!zbdd3/ubc/d!.mz!.mgm
%!/0b/pvu
4!,!6!,!6
sftvmu!;!24

13. Shift / Reduce Conflict (1/4)
Shift / Reduce Conflict
●
– . `... .. ....
.. (.... .)
–

14. Shift / Reduce Conflict (2/4)
.1 + 2 + 3.. -1
● .
S
E
E PLUS E
NUMBER
E PLUS E
NUMBER NUMBER

15. Shift / Reduce Conflict (3/4)
.1 + 2 + 3.. -2
● .
S
E
E PLUS E
NUMBER E PLUS E
NUMBER NUMBER

16. Shift / Reduce Conflict (4/4)
● .. ..( ) ..
● !. .Ä.. .

17. (1/3)
..
(lex!)
● .. . .
#,#!!!!!|!sfuvso!QMVT!~
#.#!!!!!|!sfuvso!NJOVT!~
#+#!!!!!|!sfuvso!NVMU!~
#0#!!!!!|!sfuvso!NVMU!~

18. (2/3)
..
(yacc!)
● .. . .
T!!!!!!!;!F!|!qsjoug)#sftvmu!;!e]o#-!%2*!~
!!!!!!!!
F!!!!!!!;!F!QMVT!F!|!%%!!%2!,!%4!~
!!!!!!!!}!F!NJOVT!F!|!%%!!%2!.!%4!~
!!!!!!!!}!F!NVMU!F!|!%%!!%2!+!%4!~
!!!!!!!!}!F!EJW!F!|!%%!!%2!0!%4!~
!!!!!!!!}!OVNCFS.|!%%!!%2!~
!!!!!!!!

19. (3/3)
..
●
%!gmfy!zbdd4/m
%!cjtpo!zbdd4/z
zbdd4/z;!dpogmjdut;!27!tijgu0sfevdf
%!hdd!zbdd4/ubc/d!.mz!.mgm
%!/0b/pvu
4! !4!+!3
sftvmu!;!.4
%!/0!b/pvu
!!. !!
4!+!4! !3
sftvmu!;!4

20. (1/ )
...
(yacc!)
● ... .. 
T!!!!!!!;!F!|!qsjoug)#sftvmu!;!e]o#-!%2*!~
!!!!!!!!
F!!!!!!!;!F!QMVT!U!|!%%!!%2!,!%4!~
!!!!!!!!}!F!NJOVT!U!|!%%!!%2!.!%4!~
!!!!!!!!}!U!|!%%!!%2!~
!!!!!!!!
U!!!!!!!;!U!NVMU!G!|!%%!!%2!+!%4!~
!!!!!!!!}!U!EJW!G!|!%%!!%2!0!%4!~
!!!!!!!!}!G!|!%%!!%2!~
!!!!!!!!
G!!!!!!!;!MQBS!F!SQBS!|!%%!!%3!~
!!!!!!!!}!OVNCFS!|!%%!!%2!~
!!!!!!!!

21. (2/2)
...
●
%!gmfy!zbdd5/m
%!cjtpo!zbdd5/z
%!hdd!zbdd5/ubc/d!.mz!.mgm
%!/0b/pvu
4! !4!+!3
sftvmu!;!.4
%!/0!b/pvu
GOOD!!
4!+!4! !3
sftvmu!;!8

22. .$. .

23. .$. .

24. ..=....

25. ....
/ / (. )
●
S
Shift / Reduce Conflict
●
Yacc / Lex .3
●
● ..
● ...
●
C

26. .......
● è
●
9 . .8 .
● .
– F$
–
–
●
.. ....

27. ..