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  1. /** $ gcc -std=c99 *.c -lm && (echo ' (12 32(32 12))' | ./a.out) */
  2. #include <errno.h>
  3. #include <inttypes.h> /* uintmax_t, PRIuMAX */
  4. #include <limits.h>
  5. #include <math.h>
  6. #include <stdio.h>
  7. #include <stdlib.h> /* EXIT_FAILURE */
  8. #include <string.h>
  9.  
  10. int main(void) {
  11.   long double sum = 0.0; /* result */
  12.   uintmax_t position = 0, /* the current position in the input */
  13.     depth = 0, /* how deep parens are nested */
  14.     number = 0; /* the current number */
  15.   int c;
  16.   for ( ; (c = getchar()) != EOF; ++position) {
  17.     if ('0' <= c && c <= '9') {
  18.       if (number > (UINTMAX_MAX - (c - '0')) / 10U) {
  19. 	fprintf(stderr, "error: input number is too large at (offset)%" PRIuMAX
  20. 		", limit %" PRIuMAX "\n", position, UINTMAX_MAX);
  21. 	exit(EXIT_FAILURE);
  22.       }
  23.       number = 10*number + (c - '0');
  24.     }
  25.     else { /* not a digit */
  26.       if (number) {
  27. 	/* result += a[i] * (0.5)**(b[i]) */
  28. 	errno = 0;
  29. 	sum += number * powl(.5, depth); /* number >> depth */
  30. 	if (errno) { /*NOTE: ignore `+*` math errors */
  31. 	  fprintf(stderr, "error: powl: %s at (offset)%" PRIuMAX "\n",
  32. 		  strerror(errno), position);
  33. 	  exit(EXIT_FAILURE);
  34. 	}
  35. 	number = 0; /* reset number */
  36.       }
  37.  
  38.       if (c == '(')
  39. 	++depth; /*NOTE: ignore the (unlikely) overflow */
  40.       else if (c == ')') {
  41. 	if (depth == 0) {
  42. 	  fprintf(stderr , "error: unexpected closing paren at "
  43. 		  "(offset)%" PRIuMAX "\n", position);
  44. 	  exit(EXIT_FAILURE);
  45. 	}
  46. 	--depth;
  47.       }
  48.       else if (c == '-') {
  49. 	fprintf(stderr, "error: minus sign at (offset)%" PRIuMAX
  50. 		" (program doesn't support negative numbers)\n", position);
  51. 	exit(EXIT_FAILURE);
  52.       }
  53.     }
  54.   }
  55.   if (printf("%Lf\n", sum) < 0)
  56.     exit(EXIT_FAILURE);
  57.   return feof(stdin) ? EXIT_SUCCESS : EXIT_FAILURE;
  58. }
Success #stdin #stdout 0s 2296KB
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https://ideone.com/UZE8qo
language:
C99 (gcc 8.3)
created:
9 years ago
visibility:
secret

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