Is there a way that I can get there to be only one input in my program?

1

I am writing a program where I calculate the area of a circle, the volume of a sphere, and the surface area of a sphere and I need a way to get one source of user input. I don’t want the program to keep asking for user input the way that it is in the functions.

I want my program to run like this:

Enter a radius in inches: 3.3
Area of a circle is 34.21 square inches
Volume of a sphere is 150.53 cubic inches
Surface area of a sphere is 136.85 square inches

This is what I have so far though:

#include <iostream>
#include <cmath>
#define Pi 3.1415
using namespace std;


void area_of_circle() {
  double radius;
  std::cout << "Enter a radius in inches: " << endl;
  cin >> radius;
  double areaCircle = Pi * radius * radius;
  std::cout << "The area of the circle is " << std::ceil(areaCircle * 100.0) / 100.0 << " square inches";
}


void volume_of_sphere() {
  double radius;
  std::cout << "Enter a radius in inches: " << endl;
  cin >> radius;
  double volumeSphere = (4/3) * Pi * radius * radius * radius;
  std::cout << "The volume of the sphere is " << std::ceil(volumeSphere * 100.0) / 100.0 << " cubic inches";
}

void surface_area_of_sphere() {
  double radius;
  std::cout << "Enter a radius in inches: " << endl;
  cin >> radius;
  double surfaceAreaSphere = 4 * Pi * radius * radius;
  std::cout << "The volume of the sphere is " << std::ceil(surfaceAreaSphere * 100.0) / 100.0 << " square inches";
  
}

int main() {
  area_of_circle();
  volume_of_sphere();
  surface_area_of_sphere();
}

Can someone help, please?

2

Why not create a separate function do get the input and have it return it to a global variable in main? Then, you could simply pass the value as an argument to each of the other functions you are calling and not ask for the radius in any of those. Instead, you would just output the other sentences with the calculations.

3

Do you mean this?

void input() {
  std::cout << "Enter a radius in inches: " << endl;
}
  
int main() {
  double radius;
  area_of_circle();
  volume_of_sphere();
  surface_area_of_sphere();
}
4

Does that work?

I was thinking you would get the radius value within input and then return it to a global variable. Like:

double radius = input();
 area_of_circle(radius);
 volume_of_sphere(radius);
 surface_area_of_sphere(radius);

You just have to make sure you delcare a variable to collect the input from the user and then return it.

5

I tried putting double radius = input(); into my functions and then typing

 double radius = input();
 area_of_circle(radius);
 volume_of_sphere(radius);
 surface_area_of_sphere(radius);

and it’s not working.

6

Did you declare a parameter for each function?

7

Declare a parameter as in:

void area_of_circle(radius) {
  double radius = input();
  std::cout << "Enter a radius in inches: " << endl;
  cin >> radius;
  double areaCircle = Pi * radius * radius;
  std::cout << "The area of the circle is " << std::ceil(areaCircle * 100.0) / 100.0 << " square inches";
}

int main() {
 double radius = input();
 area_of_circle(radius);
 volume_of_sphere(radius);
 surface_area_of_sphere(radius);
}
8

That is not how you declare a parameter in C++.

Also, your other functions other than input do not need to request the radius input again. Also, make sure the input function does return the radius gathered from the user entering it.

9

FYI - You need to change your volumeSphere formula a little to get the correct value for it.

10

Is this what you meant?

#include <iostream>
#include <cmath>
#define Pi 3.1415
using namespace std;

double input() {
  double radius;
  std::cout << "Enter a radius in inches: " << endl;
  cin >> radius;
  return radius;
}

void area_of_circle(double radius) {
  double areaCircle = Pi * radius * radius;
  std::cout << "The area of the circle is " << std::ceil(areaCircle * 100.0) / 100.0 << " square inches\n";
}

void volume_of_sphere(double radius) {
  double volumeSphere = (4.0/3.0) * Pi * radius * radius * radius;
  std::cout << "The volume of the sphere is " << std::ceil(volumeSphere * 100.0) / 100.0 << " cubic inches\n";
}

void surface_area_of_sphere(double radius) {
  double surfaceAreaSphere = 4 * Pi * radius * radius;
  std::cout << "The volume of the sphere is " << std::ceil(surfaceAreaSphere * 100.0) / 100.0 << " square inches";
}

int main() {
  double radius = input();
  area_of_circle(radius);
  volume_of_sphere(radius);
  surface_area_of_sphere(radius);
}
11

Looks good now. The only thing I think you would want to change is to remove the << endl after the "Enter a radius in inches: ", so that the user enters the value on the same line.