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My professor asks that we use the while function in c++ for a code we are writing. I keep returning the same error, so I wrote a simple simple code to understand the while loop. Still stuck at this part. It obviously isn't the end of my program, I just gets stuck at the while function. Any ideas?

#include <iostream>
#include <cstdlib>

using namespace std;

void response (){
    cout<<" Continue loop function?\n";
    cout <<"y - yes\nn - no\n";
    char response='y';
    cin>> response;
    return;
}
int main (){
    response ();
    while (response=='y')
    return 0;

}
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2
  • 5
    you have problem with variable scope: tutorialspoint.com/cplusplus/cpp_variable_scope.htm Commented Sep 19, 2014 at 7:52
  • 1
    +1 for writing a testcase to do your debugging. Excellent move. I can't stress how important that is!! (shame your question is mislabelled as the problem has nothing to do with loops, but never mind) Commented Sep 19, 2014 at 10:00

3 Answers 3

Reset to default
2

You can't access the function local response variable in main().

In this line 

 while (response=='y')

response is interpreted as the address of the response() function, compared to 'y' which causes the error you see.

As others mentioned you should rather have something like this

char response (){
    cout<<" Continue loop function?\n";
    cout <<"y - yes\nn - no\n";
    char resp='y';
    cin >> resp;
    return resp;
}
int main (){
    while (response()=='y'); // << also note the semicolon here
    return 0;

}
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2

There are several things wrong here. Your main function should probably look like this:

int main()
{
    while (response() == 'y')
    { //must have either an empty body or a semicolon here, 
      //otherwise our return statement will become the loop body!
    }

    return 0;
}

Also, your response() function should return the local variable response so its value can be returned to main. You can't use the response variable outside of the response function because of scope.

What your (erroneous) main function currently does is call the response() function and then try to compare your response function to the char literal 'y'. However, this isn't comparing the value just returned from your function, it's comparing the memory address (pointer) of the function itself.

C++ allows you to have variables and functions with the same same, but it's usually a bad idea. You might want to give either your response() function or the response local variable a different name.

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1 Comment

+1 for explaining where the actual warning message is coming from. Bonus points if you also point out the error(s) in response(). (the empty return with void as the type, and the horrid use of the function name as a local var).
1

While is waiting for a boolean. In order to compare 'y' to response, you must change the return type from void to char : 

char response (){
    cout<<" Continue loop function?\n";
    cout <<"y - yes\nn - no\n";
    char response='y';
    cin>> response;
    return response;
}
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