C ++从char到const char的无效转换*

Question

How do I fix this function? Error I'm getting is: invalid conversion from char to const char* on line

if(strcmp('\0', p->pubLow[i][j]) == 0) {

Code:

struct Prefix {
    int  no;             // number of entries
    int  area[MAX];      // area elements
    char pubLow[MAX][8]; // low end of publisher range
    char pubHgh[MAX][8]; // high end of publisher range
    int  pubLen[MAX];    // no of chars in publisher string
};

int minNoDigits(const Prefix* p, int area) {
    int minNoDigits = 0;
    for(int i = 0; i < p->no; i++) {
        if(area == p->area[i]) {
            cout << "p->pubLow[i] is: " << p->pubLow[i] << endl;
            minNoDigits = 1;
            for(int j = 1; j < 3; j++) {
                if(p->pubLow[i][j] = '\0') {
                    j = 3;
                    i = p->no;
                }
                else {
                    minNoDigits++;
                }
            }
        }
    }
    return minNoDigits;
}

Edit to provide more information.

I've changed the line to

if(p->pubLow[i][j] = '\0') {

New error:

assignment of read-only location p->Prefix::pubLow[i][j]

Answer 1

I understand p->pubLow[i][j] is actually a char , because pubLow seems from your code to be a char** so this is what you are looking for:

if(p->pubLow[i][j] == '\0') {

strcmp() has the following prototype:

int strcmp ( const char * str1, const char * str2 );

Here is the documentation .

So, to summarize, you are trying to compare 2 charaters and strcmp() is designed to compare 2 constant strings .

Answer 2

strcmp比较来自const char* s的字符串：

if(strcmp("", p->pubLow[i][j]) == 0) {

Answer 3

Why do you need strcmp(...) for char comparsion? You can do just

if('\0'== p->pubLow[i][j]) ...

Answer 4

'\\0' is a char not a string like other have replied.

I'm not sure what you want tot achieve with if(strcmp('\\0', p->pubLow[i][j]) == 0)

If you want to check end of string you can do this if('\\0' == p->pubLow[i][j])

Answer 5

It looks like p->pubLow[i] is a char* and you're trying to compare it character-by-character with the termination character \\0 ?

As others have pointed out, strcmp is meant to be used to compare strings not individual characters. You could use == operator to compare the characters instead, but since you're doing this to find the length of the string, it would be better to do this directly.

You want to return the number of digits in the p->pubLow[i] with the same area as area , right? How about this:

int minNoDigits(const Prefix* p, int area) {
    for(int i = 0; i < p->no; i++) {
        if(area == p->area[i]) {
            cout << "p->pubLow[i] is: " << p->pubLow[i] << endl;
            return strlen(pubLow[i]) + 1;
        }
    }
    return 0;
}

You might also find break useful in future - it will break you out of the for loops (I notice you were setting j and i directly to do this).