C 下标值不是数组、指针或向量 - 是吗？

Posted 2023-02-16

【中文标题】C 下标值不是数组、指针或向量 - 是吗？

【英文标题】：C Subscripted value is not an array, pointer, or vector - Yes it is?

【发布时间】：2016-06-13 04:05:14

【问题描述】：

我构建了一个应用，它使用 Vigenere 密码对单词或句子进行编码。它可以工作，但所有内容都包含在 main() 中。我正在使用函数重建应用程序。但是当我认为它是一个数组时，我收到错误“下标值不是数组、指针或向量”。

错误由此而来

if ((int)sentencetoencode[repeatciphercounter] < 65 || ((int)sentencetoencode[repeatciphercounter] > 90 && (int)sentencetoencode[repeatciphercounter] < 97) || (int)sentencetoencode[repeatciphercounter] > 122)
    
        ciphersentence[repeatciphercounter] = (char)32;

关于将“char [100]”传递给“char”参数类型的不兼容指针的附加警告

CipherRepeater(sentencetoencode, cipherwordtorepeat, ciphersentence);

完整代码

#include <stdio.h>
#include <string.h>

char CipherRepeater(char sentencetoencode, char cipherwordtorepeat, char ciphersentence);

int main(int argc, char * argv[])

// This is a message to encode using Vigenere cipher
char sentencetoencode[100] = "secret message is come over at five";

// Pass a word at command line, then assign that word to cipherwordtorepeat
// This word is the Vigenere encoding key
// Example word: cat
char cipherwordtorepeat[100];

for(unsigned long argvcounter = 0, argvlength = strlen(argv[1]); argvcounter < argvlength; argvcounter++)

    cipherwordtorepeat[argvcounter] = argv[1][argvcounter];


// Now the word cat needs to be repeated until it matches the length of the message
// Example "secret message is come over at five"
//         "catcat catcatc at catc atca tc atca"
// Declare an array of characters
// Then the function fills the array with the repeating word
char ciphersentence[100];
CipherRepeater(sentencetoencode, cipherwordtorepeat, ciphersentence);

printf("%s\n", ciphersentence);

return 0;


char CipherRepeater(char sentencetoencode, char cipherwordtorepeat, char ciphersentence)

// Create a counter to make sure to go back to char 0 in the word array when end is reached
int endofwordcounter = 0;
unsigned long cipherwordlength = strlen(&cipherwordtorepeat);

// Take the cipher word and repeat it until it's the same length as the word to encode
for (unsigned long repeatciphercounter = 0, sentencetoencodelength = strlen(&sentencetoencode); repeatciphercounter < sentencetoencodelength; repeatciphercounter++)

    // Put a space in the new string in any spot where a non-letter is used
    if ((int)sentencetoencode[repeatciphercounter] < 65 || ((int)sentencetoencode[repeatciphercounter] > 90 && (int)sentencetoencode[repeatciphercounter] < 97) || (int)sentencetoencode[repeatciphercounter] > 122)
    
        ciphersentence[repeatciphercounter] = (char)32;
    
    else
    
        // Copy the character
        ciphersentence[repeatciphercounter] = cipherwordtorepeat[endofwordcounter];
        endofwordcounter++;
        if (endofwordcounter >= cipherwordlength)
        
            endofwordcounter = 0;
        
    


return 0;

【问题讨论】：

char cipherwordtorepeat 表示cipherwordtorepeat 是单个字符（因此不是数组、指针或向量）

你需要了解char、char []和char *之间的区别。第一个是单个字符，而不是字符串。第二个是字符数组。第三个是指向字符的指针。指向的字符可能是字符数组的成员。 char [] 可以转换为char *，实际上是在表达式上下文中使用时。

【参考方案1】：

您的 sentencetoencode 声明为

// This is a message to encode using Vigenere cipher
char sentencetoencode[100] = "secret message is come over at five";

但您的 CipherRepeater 被声明为

char CipherRepeater(char sentencetoencode, char cipherwordtorepeat,
                        char ciphersentence);

接受char 而不是char*。您正在将char* 传递给该函数 这是产生错误

incompatible pointer to integer conversion passing 'char [100]' to parameter type of 'char'

所以将char 更改为char*。

并且还将strlen(&cipherwordtorepeat) 替换为strlen(cipherwordtorepeat)，并与for 循环中的另一个strlen 类似。

【讨论】：

好的，有道理。但是在切换到 char* 后，我仍然遇到其中三个错误。都在上面相同的 if 语句中。

我的警告从 1 变为 5。同样的警告。

你能说出警告吗？

代码：CipherRepeater(sentencetoencode, cipherwordtorpeat, ciphersentence);提供指向将“char [100]”传递给参数类型“char”的整数转换的不兼容指针

代码：unsigned long cipherwordlength = strlen(cipherwordtorpeat);将不兼容的整数传递给指针转换，将“char”传递给“const char*”类型的参数