How To Think Like a Computer Scientist C++ Edition The Pretext Interactive Version

You can read the values of an instance variable using the same syntax we used to write them:

int x = blank.x;

The expression blank.x means “go to the object named blank and get the value of x.” In this case we assign that value to a local variable named x. Notice that there is no conflict between the local variable named x and the instance variable named x. The purpose of dot notation is to identify which variable you are referring to unambiguously.

You can use dot notation as part of any C++ expression, so the following are legal.

cout << blank.x << ", " << blank.y << endl;
double distance = sqrt(blank.x * blank.x + blank.y * blank.y);

struct Blue {
  double x, y;
};

int main() {
  Blue blank;
  blank.x = 7.0;
  blank.y = 2.0;
  cout << blank.y << blank.x;
  double distance = blank.x * blank.x + blank.y * blank.y;
  cout << distance << endl;
}