将无返回值void函数改造为带返回值函数并在main中输出变量z

Got it, let's work through this. You originally had a void function trackVar that calculated a local variable z and printed it directly. But you wanted to let main() handle the output instead, which meant you needed to pass that z value back to main() instead of printing it inside the function. Here's how to refactor your code correctly:

Original Code #

#include <iostream>
#include <cmath>
#include <iomanip>
using namespace std;

void trackVar(double& x, double y);
int main() {
 double one, two;
 cout << fixed << showpoint << setprecision(2);
 cout << "Enter two numbers: ";
 cin >> one >> two;
 cout << endl;
 trackVar(one, two);
 cout << "one = " << one << ", two = " << two << endl;
 trackVar(two, one);
 cout << "one = " << one << ", two = " << two << endl;
 return 0;
}
void trackVar(double& x, double y) {
 double z;
 z = floor(x) + ceil(y);
 x = x + z;
 y = y - z;
 cout << "z = " << z << ", ";
}

Refactored Code (With z Returned to Main) #

#include <iostream>
#include <cmath>
#include <iomanip>
using namespace std;

double trackVar(double& x, double y); // Updated prototype to return double
int main() {
 double one, two, z; // Added z variable to capture returned value
 cout << fixed << showpoint << setprecision(2);
 cout << "Enter two numbers: ";
 cin >> one >> two;
 cout << endl;
 
 z = trackVar(one, two); // Assign returned z to our main variable
 cout << "z = " << z << ", one = " << one << ", two = " << two << endl;
 
 z = trackVar(two, one); // Capture z again for the second call
 cout << "z = " << z << ", one = " << one << ", two = " << two << endl;
 return 0;
}
double trackVar(double& x, double y) {
 double z;
 z = floor(x) + ceil(y);
 x = x + z;
 // Note: y is passed by value, so modifying it here doesn't affect main's variables
 y = y - z;
 return z; // Return z to the caller (main)
}

Key Changes Explained #

• Updated Return Type: Changed trackVar from void to double so it can send the z value back to main().
• Modified Prototype: The function declaration now matches the new return type to avoid compiler errors.
• Capture Return Value: Added a double z in main() to store the value returned by each call to trackVar.
• Moved Output to Main: Removed the cout inside trackVar—now all printing happens in main(), keeping the function focused on calculation rather than I/O.
• Pass-by-Value Note: The y parameter is passed by value, so modifying it inside trackVar doesn't change the original variable in main()—this preserves your original program's behavior for y.

内容的提问来源于stack exchange，提问作者Ian