How to evaluate operations then print a message - c++

Question

Take 4 variables from user w, x ,y ,z.
If w ‘x’ y = z print “You are right” otherwise, print
“ERROR
Below is the code I created for this problem, but it seems there is something wrong.
#include<iostream>
using namespace std;
void calculate(int w, char x, int y, int z)
{
if (x == '+') {
int z = w + y ;
cout << "You are right" <<endl;
}
else if (x == '-') {
int z = w - y ;
cout << "You are right" << endl;
}
else if (x == '*') {
int z = x * y;
cout << "You are right" << endl;
}
else
cout << "Error!" << endl;
}
int main()
{
int w, y, z;
char x;
cout << "Enter values for w, x, y, and z: " << endl;
cin >> w >> x >> y >> z;
cout << endl;
calculate(w, y, x, z);
return 0;
}

Answer 1

void calculate(int w, char x, int y, int z)
{
if (x == '+') {
int z = w + y ;
cout << "You are right" <<endl;
}
else if (x == '-') {
int z = w - y ;
cout << "You are right" << endl;
}
else if (x == '*') {
int z = x * y;
cout << "You are right" << endl;
}
else
cout << "Error!" << endl;
}
If you look closely int z = w + y is wrong as you are already taking z as a function parameter.
The correct statement, however, would be z = w + y.
The second thing, you need to remove int z from your function parameters, but declare and define it inside the function body. This is because when you pass z from main(), you aren't really passing the variable z. But merely the value of it which will get copied into int z in calculate.
Passing z as a reference
If you want the z in your main to update, you shall pass the value by reference.
void calculate(int w,char x,int y,int& z)
{
//updating z
}
Now, if you apply any change to z in calculate(), it will also appear your main().
Another solution is to to return int from the function and assign to the variable z in main().
#include <iostream>
int calculate(int w,int y,char x)
{
switch(x)
{
case '+':
std::cout << "You are right!\n";
return w+y;
case '-':
std::cout << "You are right!\n";
return w-y;
case '*':
std::cout << "You are right!\n";
return w*y;
default:
std::cout << "You are wrong!\n";
break;
}
}
int main()
{
int w = 5;
int y = 10;
char x = '+';
int z = calculate(w,y,x);
std::cout << z;
return 0;
}