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  1. /* A very simple cdecl clone by FredOverflow.
  2.    Functions are not supported yet, only pointers and arrays.
  3.    Error detection should be pretty good. */
  4.  
  5. #include <ctype.h>
  6. #include <stdio.h>
  7. #include <stdlib.h>
  8. #include <string.h>
  9.  
  10. void assume(int condition, const char * error_message)
  11. {
  12.     if (!condition)
  13.     {
  14.         fprintf(stderr, "%s\n", error_message);
  15.         exit(1);
  16.     }
  17. }
  18.  
  19. void remove_spaces(char * dst)
  20. {
  21.     while (!isspace(*dst)) ++dst;
  22.     char * src = dst;
  23.     while (*src)
  24.     {
  25.         if (!isspace(*src))
  26.         {
  27.             *dst++ = *src;
  28.         }
  29.         ++src;
  30.     }
  31.     *dst = 0;
  32. }
  33.  
  34. /* Yes I know, global variables are evil, kittens die etc...
  35.    In an object-oriented language, this would be a private field, okay? */
  36. static char * p;
  37.  
  38. void skip(int predicate(int))
  39. {
  40.     while (predicate(*p))
  41.     {
  42.         ++p;
  43.     }
  44. }
  45.  
  46. int is_star(int x)
  47. {
  48.     return '*' == x;
  49. }
  50.  
  51. int parse_int()
  52. {
  53.     int x = 0;
  54.     while (isalnum(*p))
  55.     {
  56.         x = x * 10 + (*p++ - '0');
  57.     } 
  58.     return x;
  59. }
  60.  
  61. void parse_declarator();
  62. void parse_atom();
  63. void parse_array();
  64.  
  65. void declaration()
  66. {
  67.     skip(isspace);
  68.     assume(isalpha(*p), "must start with a letter");
  69.  
  70.     char * begin_of_type = p;
  71.     skip(isalnum);
  72.     char * end_of_type = p;
  73.  
  74.     remove_spaces(p);
  75.     parse_declarator();
  76.  
  77.     *end_of_type = 0;
  78.     printf("%s\n", begin_of_type);
  79. }
  80.  
  81. int count_stars()
  82. {
  83.     char * first_star = p;
  84.     skip(is_star);
  85.     return p - first_star;
  86. }
  87.  
  88. void print_stars(int number_of_stars)
  89. {
  90.     int i;
  91.     for (i = 0; i < number_of_stars; ++i)
  92.     {
  93.         printf("pointer to ");
  94.     }
  95. }
  96.  
  97. void parse_declarator()
  98. {
  99.     int number_of_stars = count_stars();
  100.     parse_atom();
  101.     parse_array();
  102.     print_stars(number_of_stars);
  103. }
  104.  
  105. void parse_atom()
  106. {
  107.     if ('(' == *p)
  108.     {
  109.         ++p;
  110.         parse_declarator();
  111.         assume(')' == *p, "missing )");
  112.         ++p;
  113.     }
  114.     else skip(isalnum);
  115. }
  116.  
  117. void parse_array()
  118. {
  119.     while ('[' == *p)
  120.     {
  121.         ++p;
  122.         int n = parse_int();
  123.         assume(']' == *p, "missing ]");
  124.         ++p;
  125.         printf("array of %d ", n);
  126.     }
  127. }
  128.  
  129. int main()
  130. {
  131.     char test[] = " int ** (* a[ 2 ]) [3 ][5 ]  [7]   ";
  132.     printf("%s\n", test);
  133.  
  134.     p = test;
  135.     declaration();
  136.  
  137.     return 0;
  138. }
  139.  
Success #stdin #stdout 0s 2292KB
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stdin
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Standard input is empty
stdout
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 int ** (* a[ 2 ]) [3 ][5 ]  [7]   
array of 2 pointer to array of 3 array of 5 array of 7 pointer to pointer to int
https://ideone.com/rhOcee
language:
C99 (gcc 8.3)
created:
9 years ago
visibility:
secret

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