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  1. %{
  2. #include <stdio.h>
  3. %}
  4.  
  5. %define INITIAL 0
  6. %define SAW_A   1
  7. %define SAW_AB  2
  8. %define SAW_ABA 3
  9.  
  10. %%
  11.  
  12. /* Define transitions for 'a' and 'b' */
  13. a   {
  14.         if (state == INITIAL) state = SAW_A;      /* Transition from q0 to q1 */
  15.         else if (state == SAW_A) state = SAW_A;    /* Stay in q1 */
  16.         else if (state == SAW_AB) state = SAW_ABA; /* Transition from q2 to q3 */
  17.     }
  18.  
  19. b   {
  20.         if (state == INITIAL) state = INITIAL;    /* Stay in q0 */
  21.         else if (state == SAW_A) state = SAW_AB;  /* Transition from q1 to q2 */
  22.         else if (state == SAW_AB) state = INITIAL;/* Transition from q2 to q0 (reset) */
  23.         else if (state == SAW_ABA) state = SAW_ABA;/* Stay in q3 */
  24.     }
  25.  
  26. .   /* Ignore any other characters */
  27.  
  28. %%
  29.  
  30. /* Main function to drive the Lex program */
  31. int main() {
  32.     int state = INITIAL;  /* Start in state q0 */
  33.  
  34.     yylex();  /* Invoke Lex to process the input */
  35.  
  36.     if (state == SAW_ABA) {
  37.         printf("Input string contains the substring 'aba'.\n");
  38.     } else {
  39.         printf("Input string does not contain the substring 'aba'.\n");
  40.     }
  41.  
  42.     return 0;
  43. }
  44.  
Success #stdin #stdout #stderr 0.03s 6808KB
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Standard input is empty
stdout
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Standard output is empty
stderr
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ERROR: /home/ikcXFa/prog:2:1: Syntax error: Operator expected
ERROR: /home/ikcXFa/prog:43:1: Syntax error: Unexpected end of file
ERROR: '$runtoplevel'/0: Undefined procedure: program/0
   Exception: (3) program ? EOF: exit
https://ideone.com/y18o2t
language:
Prolog (swi 7.6.4)
created:
9 days ago
visibility:
public

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