使用C字符串时出错

Question

I have a simple example from a C++ textbook that defines a C-String and then loops to replace all the elements that are not the \\0 character with X.

char ourString[5] = "Hi";
int index = 0;
while(ourString[index] != "\0")
{
    ourString[index] = "X";
    index++;
}

cout << ourString[] << endl;

However when I compile and run I get the following error:

C:\Users\Ben\Dropbox\Learning Programming\C++\Strings\Strings.cpp||In function 'int main()':|
C:\Users\Ben\Dropbox\Learning Programming\C++\Strings\Strings.cpp|17|error: ISO C++ forbids comparison between pointer and integer [-fpermissive]|
C:\Users\Ben\Dropbox\Learning Programming\C++\Strings\Strings.cpp|19|error: invalid conversion from 'const char*' to 'char' [-fpermissive]|
C:\Users\Ben\Dropbox\Learning Programming\C++\Strings\Strings.cpp|23|error: expected primary-expression before ']' token|
||=== Build finished: 3 errors, 0 warnings (0 minutes, 0 seconds) ===|

I don't see the problem why it's not letting me (as far as I can understand the error) compare the elements which are characters, to the character \\0. I don't think I am trying to compare a pointer to an integer...

Answer 1

You need use single quotes in two places.

while(ourString[index] != '\0')
{
    ourString[index] = 'X';
    index++;
}

Since you have double quotes, it's considered as string literal.

Answer 2

Change "\\0" to '\\0' . The first is a string literal that decays to a pointer, and as compiler told you, you're not allowed to compare pointers to integers. The latter is a plain old character literal.

The same goes for ourString[index] = "X"; , change "X" to 'X' .

And the last line should be cout << ourString << endl; ;

Answer 3

You're confusing characters with strings. You need to switch the "\\0" to '\\0' and "X" to 'X' . Also you should not use [] on the cout statement - combining these gives:

char ourString[5] = "Hi";
int index = 0;
while(ourString[index] != '\0')
{
    ourString[index] = 'X';
    index++;
}

cout << ourString << endl;

Note that you can write this in a neater form:

for( char* c = ourString; *c ; ++c) // *c is the same as *c!='\0'
{
  *c='X';
}
cout << ourString << endl;

Answer 4

replace while(ourString[index] != "\\0")

with

while(ourString[index] != '\\0')

Replace double ticks with single ones.

Answer 5

you used a null operator, it is not used with double quotation "" it always used with single quotation '\\0'

try this,,

  while(ourString[index] != '\0')