String Problem

I have some code, that have error that I cannot repair by myself:

Code:

int main(){
   string a;
   int i;
   for(i=0;i<=a.size()-1;i++){
       if(a[i]!="b"){
          //do something
   }
}

at line : if(a[i]!="b" have error: ISOC++ forbids comparison between pointer and integer.
So, who help me on this error, please.

thanks

What is the type of "a"?

I don't know why your ask like it: because my code isn't clear, or you want me to look more deeply my code, because it's question too stupid.
Of course, type of a is string, and a[i] is a character(I think)

> a[i]!="b"

Here a[i] is a char and "b" is possibly a const char *

If you want the character 'b' ; say 'b' !


Edit: Now I see... Laserlight didn't ask you the type of a , It was "a" !!

Originally Posted by hqt

I don't know why your ask like it: because my code isn't clear, or you want me to look more deeply my code, because it's question too stupid.
Of course, type of a is string, and a[i] is a character(I think)

I made a typographical error: I intended to ask what is the type of "b".

Just a heads up, but this
>>for(i=0;i<=a.size()-1;i++)
Is common written as
for(int i = 0; i < a.size(); i++)

You may do as you please, of course.

Originally Posted by Elysia

Just a heads up, but this
>>for(i=0;i<=a.size()-1;i++)
Is common written as
for(int i = 0; i < a.size(); i++)

And is uncommonly written as

Code:

for(auto i : a)

No 'messy' operators !

Originally Posted by hqt

I have some code, that have error that I cannot repair by myself:

Code:

int main(){
   string a;
   int i;
   for(i=0;i<=a.size()-1;i++){
       if(a[i]!="b"){
          //do something
   }
}

at line : if(a[i]!="b" have error: ISOC++ forbids comparison between pointer and integer.
So, who help me on this error, please.

thanks

OK, I will ask. What are you trying to do? Big picture here.

Try this:

Code:

int main()
{
    string a = "abc";
    int i;
    for(i = 0; i <= (int)a.size()-1; i++)
    {
        if(a[i] != 'b')
        {
            cout << "Not b, found " << a[i] << endl;
        }
        else
            cout << "Found b" << endl;
    }

    return 0;
}

Originally Posted by hqt

I have some code, that have error that I cannot repair by myself:

Code:

int main(){
   string a;
   int i;
   for(i=0;i<=a.size()-1;i++){
       if(a[i]!="b"){
          //do something
   }
}

at line : if(a[i]!="b" have error: ISOC++ forbids comparison between pointer and integer.
So, who help me on this error, please.

thanks

There is no need for a cast, let alone a C style cast here.

But then again, i shouldn't be an int either. It should be a std::string::size_t or std::size_t. By removing the cast, you may get a warning (unless using correct type for i).

For some reason my compiler is giving me this:

"warning C4018: '<=' : signed/unsigned mismatch" when I don't cast. No errors when I do...any ideas why that is?

Originally Posted by rmatze

For some reason my compiler is giving me this:

"warning C4018: '<=' : signed/unsigned mismatch" when I don't cast. No errors when I do...any ideas why that is?

Yes, I do:

Originally Posted by Elysia

But then again, i shouldn't be an int either. It should be a std::string::size_t or std::size_t. By removing the cast, you may get a warning (unless using correct type for i).

My main point was the solution wasn't optimal depending on what the OP was exactly trying to do.

Ahhh yes, I read over your post to fast. Fixed.