8.5. Structures as parameters

You can pass structures as parameters in the usual way. For example,

void printPoint (Point p) {
  cout << "(" << p.x << ", " << p.y << ")" << endl;
}

printPoint takes a point as an argument and outputs it in the standard format. If you call printPoint (blank), it will output (3, 4).

The active code below uses the printPoint function. Run the code to see the output!

#include <iostream> using namespace std; struct Point { double x, y; }; void printPoint (Point p) { cout << "(" << p.x << ", " << p.y << ")" << endl; } int main() { Point blank = { 3.0, 4.0 }; printPoint (blank); }

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As a second example, we can rewrite the distance function from Section 5.2 so that it takes two Points as parameters instead of four doubles.

double distance (Point p1, Point p2) {
  double dx = p2.x - p1.x;
  double dy = p2.y - p1.y;
  return sqrt (dx*dx + dy*dy);
}

The active code below uses the updated version of the distance function. Feel free to modify the code!

#include <iostream> #include <cmath> using namespace std; struct Point { double x, y; }; double distance (Point p1, Point p2) { double dx = p2.x - p1.x; double dy = p2.y - p1.y; return sqrt (dx*dx + dy*dy); } int main() { Point origin = { 0.0, 0.0 }; Point point = { 3.0, 4.0 }; cout << "The distance from the point to the origin is " << distance (origin, point) << endl; }

Q-3: What will print?

struct Coordinate {
  int x, y;
};

void printOppositeCoordinate (Coordinate p) {
  cout << "(" << -p.y << ", " << -p.x << ")" << endl;
}

int main() {
  Coordinate coord = { 2, 7 };
  printOppositeCoordinate (coord);
}

• (-2, -7)

• Take a close look at the printOppositeCoordinate function.

• (2.0, 7.0)

• Take a close look at the printOppositeCoordinate function.

• (-7, -2)

• Yes, this is the correct output.

• (-7.0, -2.0)

• Take a close look at the Coordinate struct.

Construct a function that takes in three Point structures and prints the average of the x coordinates and the average of the y coordinates as a coordinate. Find the x average before the y average.

        void printAveragePoint(Point p1, Point p2, Point p3) {
---
 double avgX = (p1.x + p2.x + p3.x)/3;
---
 double avgY = (p1.y + p2.y + p3.y)/3;
---
 double avgY = (y.p1 + y.p2 + y.p3)/3; #distractor
---
 cout << "(" << avgX << "," << avgY << ")";
---
 cout << "(" << "avgX" << "," << "avgY" << ")"; #distractor
---
}
        

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