assert(str_length("String") == 6);
  assert(str_length(" ") == 1);
  assert(str_length("ABC") == 3);
  assert(str_length("0a jsd 00") == 9);
  assert(str_occur("tester", "te") == 2);
  assert(str_occur("eeeee", "ee") == 4);
  assert(str_occur("ABCBABABA", "AB") == 3);
  assert(str_occur("ABC", "ABC ") == 0);
  assert(str_occur("String", "String") == 1);
  assert(str_occur("h sdfghjklasihdh ", "h ") == 2);
  assert(is_palindrome("racecar") == true);
  assert(is_palindrome("race car") == true);
  assert(is_palindrome("12345") == true);
  assert(is_palindrome("    abcBA") == true);
  assert(is_palindrome(";#:@/@;!x;#/&:x") == true);
  assert(is_palindrome("abcdcb") == false);
  assert(is_palindrome("abcdba") == false);
  assert(is_palindrome("A") == true);
  assert(is_palindrome("x--==123y;'.///x") == true);
  assert(is_isogram("abcdefghij") == true);
  assert(is_isogram("a wo rd") == true);
  assert(is_isogram("wertyuiop123444444444444444444444444") == true);
  assert(is_isogram("1238 ") == true);
  assert(is_isogram("askd!$") == true);
  assert(is_isogram("Akajdn") == false);
  assert(is_isogram("Bsa a ") == false);
  assert(is_anagram("restful", "fluster") == true);
  assert(is_anagram("a word", "aword") == true);
  assert(is_anagram("r.e.s-t+f!u%l", "fluster") == true);
  assert(is_anagram("(*&(*&*&(*&(*&%%$%$", "%$%#$#$#") == true);
  assert(is_anagram("abc", "abc") == true);
  assert(is_anagram("a", " ") == false);
  assert(is_anagram("Abc @,", "##a b c") == true);