在函数返回之间进行选择

Question

我写了一个函数，它有两个不同的返回选项:

//function to compare the strings in function3
int compare(char* str, char* dest){
  int answer;
  int i;
 int length;
  length = strlen(str);
  // int jlength;
  // jlength = strlen(dest);
  for(i=0; i<length; i++){
    if(str[i] == dest[i]){
      answer = 1;
    }else {
      answer = 2;
    }
  }
  return answer;
}

我想稍后使用这个函数，并根据函数返回的内容发生不同的事情。以下是我如何构建它的相关部分:

 //compare the reversed str with the orignal, now stored in dest
  compare(str, dest);
  int function3answer;
  if(compare == 1){
    function3answer = 1;
  }else{
   function3answer = 2;
  }
  return function3answer; 
}

编译时出现错误:

warning: comparison between pointer and integer [enabled by default]

在 1 周围添加单引号没有帮助(而且也不是我真正想要的，因为我没有引用数组的一部分)，也没有将它减少到一个等号(这会产生不同的警告)。

非常感谢!

Answer 1

错误

warning: comparison between pointer and integer [enabled by default]

来自这一行:

if(compare == 1){

您尝试将一个函数与一个整数进行比较。

要消除此错误，请使用 compare 更改函数:

void some_function(...) {
    //compare the reversed str with the orignal, now stored in dest
    int compare_result = compare(str, dest);

    int function3answer;

    if(compare_result == 1){
        function3answer = 1;
    }else{
        function3answer = 2;
    }
    return function3answer; 
}

现在，compare 函数。您实现它的方式不会像您预期的那样工作:

• 如果比较 "abc" 和 "poc"，您将在 for 循环中得到:

  i = 0, str[0] == 'a', dest[0] == 'p' ==> answer = 2
  i = 1, str[0] == 'b', dest[0] == 'o' ==> answer = 2
  i = 2, str[0] == 'c', dest[0] == 'c' ==> answer = 1
  i = 3, going out for loop and returning **1**.
  

• 最糟糕的是，如果将 “a long string” 与 “tiny” 进行比较，当 i 为4.

您可以这样更正 compare 函数:

#define STRING_IDENTICAL 1
#define STRING_DIFFERENT 2

//function to compare the strings in function3
int compare(char* str, char* dest)
{
    int answer;
    int i;
    int length;
    length = strlen(str);
    int jlength;
    jlength = strlen(dest);

    if (length != jlength)
    {
        /* since size are differents, string are differents */
        return STRING_DIFFERENT;
    }

    for(i=0; i<length; i++){
        if(str[i] != dest[i]){
            /* at least one different character, string are differents */
            return STRING_DIFFERENT;
        }
    }

    /* if we reach this point, that means that string are identical */
    return STRING_IDENTICAL;
}