‘r’ was not declared in this scope

This error message typically occurs when you try to use a variable or identifier that has not been declared or defined in the current scope.

For example, if you have the following code:

void myFunction() {
  int x = 10;
  cout << r << endl;
}

You will get the error message "'r' was not declared in this scope" because the variable "r" has not been declared or defined in the function "myFunction".

To fix this error, you need to make sure that all variables and identifiers are properly declared and defined before they are used. For example, you can declare and define the variable "r" before using it in the function:

void myFunction() {
  int x = 10;
  int r = 5;
  cout << r << endl;
}