text: #include <stdlib.h>
  #include <string.h>
  
  #include "strutil.h"
  
  
  /**
   * Sets alphabetic characters to lowercase.
   * Argument(s):
   *   char *string: The original string.
   * Returns: the lowercase string.
   * (Pointer must be freed)
   */
  char * strutil_lowercase(char *string) {
      size_t length = strlen(string);
      char *lower = calloc(length + 1, sizeof(char));
  
      for (size_t i = 0; i < length; i++) {
          if (string[i] >= 'A' && string[i] <= 'Z') {
              lower[i] = string[i] + 32;
          } else {
              lower[i] = string[i];
          }
      }
  
      return lower;
  }
  