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  1. %{
  2. #include <stdio.h>
  3. #include <stdlib.h>
  4.  
  5. int state = 0; // Initial state: (even, even)
  6. %}
  7.  
  8. %option noyywrap
  9.  
  10. %%
  11.  
  12. // Transition rules based on input characters
  13. a   { 
  14.         if (state == 0) state = 1; // (even, even) -> (odd, even)
  15.         else if (state == 1) state = 0; // (odd, even) -> (even, even)
  16.         else if (state == 2) state = 3; // (even, odd) -> (odd, odd)
  17.         else if (state == 3) state = 2; // (odd, odd) -> (even, odd)
  18.     }
  19.  
  20. b   { 
  21.         if (state == 0) state = 2; // (even, even) -> (even, odd)
  22.         else if (state == 1) state = 3; // (odd, even) -> (odd, odd)
  23.         else if (state == 2) state = 0; // (even, odd) -> (even, even)
  24.         else if (state == 3) state = 1; // (odd, odd) -> (odd, even)
  25.     }
  26.  
  27. [ \t\n]+  ; // Ignore whitespace
  28.  
  29. .   { /* Ignore any other character */ }
  30.  
  31. %%
  32.  
  33. // Main function
  34. int main(int argc, char **argv) {
  35.     yylex(); // Start the lexer
  36.     if (state == 0) {
  37.         printf("Accepted: The string has an even number of 'a's and 'b's.\n");
  38.     } else {
  39.         printf("Rejected: The string does not have an even number of 'a's and 'b's.\n");
  40.     }
  41.     return 0;
  42. }
Success #stdin #stdout #stderr 0.03s 6840KB
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Standard input is empty
stdout
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Standard output is empty
stderr
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ERROR: /home/sM3rS2/prog:2:1: Syntax error: Operator expected
ERROR: /home/sM3rS2/prog:42:0: Syntax error: Unexpected end of file
ERROR: '$runtoplevel'/0: Undefined procedure: program/0
   Exception: (3) program ? EOF: exit
https://ideone.com/9vQdEL
language:
Prolog (swi 7.6.4)
created:
18 hours ago
visibility:
public

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