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  1. // Join items on output stream. (3.00)
  2.  
  3. #include <stdio.h>
  4.  
  5. void ostream_join(
  6.     const void *base, size_t nitems, size_t itemsize,
  7.     void (*putitem)(const void *item, FILE *stream),
  8.     const char* separator, FILE *stream, _Bool reverse)
  9. {
  10.     const char *first = base, *last = first + nitems*itemsize;
  11.     if (first != last) {
  12.         for (;;) {
  13.             if (reverse) {
  14.                 last -= itemsize;
  15.                 putitem(last, stream);
  16.             } else {
  17.                 putitem(first, stream);
  18.                 first += itemsize;
  19.             }
  20.             if (first == last) break;
  21.             fputs(separator, stream);
  22.         }
  23.     }
  24. }
  25.  
  26. // Use.
  27.  
  28. void putint(const void *item, FILE *stream)
  29. {
  30.     fprintf(stream, "%d", *(const int *) item);
  31. }
  32.  
  33. void print_ints_backward(const int *a, size_t n, int end)
  34. {
  35.     putchar('[');
  36.     ostream_join(a, n, sizeof *a, putint, ", ", stdout, 1);
  37.     putchar(']');
  38.     putchar(end);
  39. }
  40.  
  41. int main(void)
  42. {
  43.     int a[] = {1, 2, 3, 4};
  44.     print_ints_backward(a, sizeof a / sizeof *a, '\n');
  45.     return 0;
  46. }
Success #stdin #stdout 0s 5280KB
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stdin
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Standard input is empty
stdout
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[4, 3, 2, 1]
https://ideone.com/RiCUnp
language:
C (gcc 8.3)
created:
9 days ago
visibility:
public

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