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  1. #include <stdio.h>
  2. #include <stdlib.h>
  3.  
  4. typedef void effector(int);
  5. typedef struct transition transition;
  6. struct transition {
  7.   int state;
  8.   effector *effect;
  9. };
  10.  
  11. enum sigil { Letter, EndOfFile };
  12. typedef enum sigil sigil;
  13.  
  14. sigil sigilify(int c) {
  15.   switch (c) {
  16.     case EOF:  return EndOfFile;
  17.     default:   return Letter;
  18.   }
  19. }
  20.  
  21. void push   (int c);
  22. void pop    (int c);
  23. void swap   (int c);
  24. void halt   (int c);
  25.  
  26. #define T(state, sigil) (((state) << 1) | sigil)
  27.  
  28. int main() {
  29.   transition state = { 0, push };
  30.   transition table[] = {
  31.     [T(0, Letter)]={ 1, push },    [T(0, EndOfFile)]={ 0, halt },
  32.     [T(1, Letter)]={ 0, swap },    [T(1, EndOfFile)]={ 0, pop  },
  33.   };
  34.  
  35.   for (;;) {
  36.     int c = getchar();
  37.     (state = table[T(state.state, sigilify(c))]).effect(c);
  38.   }
  39. }
  40.  
  41. int b;
  42.  
  43. void push   (int c) { b = c; }
  44. void pop    (int c) { putchar(b); }
  45. void swap   (int c) { putchar(c); pop(0); }
  46. void halt   (int c) { exit(EXIT_SUCCESS); }
  47.  
  48.  
Success #stdin #stdout 0s 9424KB
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https://ideone.com/DdKmwq
language:
C99 (gcc 8.3)
created:
6 years ago
visibility:
public

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