8.5. Structures as parameters

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

void print_point (point p) {
  cout << "(" << p.x << ", " << p.y << ")" << endl;
}

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

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

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

As a second example, we can rewrite the distance function from Section [distance] 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 {
  double x, y;
};

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

int main() {
  coordinate coord = { 2.0, 7.0 };
  print_opposite_coordinate (coord);
}

• (-2.0, -7.0)
• Take a close look at the print_opposite_coordinate function.
• (2.0, 7.0)
• Take a close look at the print_opposite_coordinate function.
• (-7.0, -2.0)
• Yes, this is the correct output.
• (7.0, 2.0)
• Take a close look at the print_opposite_coordinate function.

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 print_average_point(point p1, point p2, point p3) {
---
 double avg_x = (p1.x + p2.x + p3.x)/3;
---
 double avg_y = (p1.y + p2.y + p3.y)/3;
---
 double avg_y = (y.p1 + y.p2 + y.p3)/3; #distractor
---
 cout << "(" << avg_x << "," << avg_y << ")";
---
 cout << "(" << "avg_x" << "," << "avg_y" << ")"; #distractor
---
}
        

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