Using a function's local variable in main - c++

Question

I tried searching for awnsers, but all the threads are different langs.
#include <cstdlib>
#include <iostream>
#include <math.h>
using namespace std;
void calcDistance (int x1, int y1, int x2, int y2);
int main()
{
int x1, y1, x2, y2;
cout << "Enter the points in coordinate pair form, ommiting parantheses" << endl;
cin >> x1 >> y1 >> x2 >> y2;
calcDistance (x1, y1, x2, y2);
system("pause");
// how do I cout the dist in main-- says dist isn't declared
}
void calcDistance (int x1, int y1, int x2, int y2)
{
int sideA;
sideA = x2 - x1;
int sideB;
sideB = y2 -y1;
int sideAsqd;
sideAsqd = sideA * sideA;
int sideBsqd;
sideBsqd = sideB * sideB;
int sideCsqd;
sideCsqd = sideAsqd + sideBsqd;
double dist;
dist = sqrt(sideCsqd);
cout << "The calculated distance is "<< dist << endl;
}
How do I make the second cout occur in main. I try just putting it in main, but then I get an error saying that dist is not declared in the scope.
I want to be able to use the dist value in main, while it has been calculated in the function.

Answer 1

Change your function:
double calcDistance (int x1, int y1, int x2, int y2)
{
int sideA = x2 - x1;
int sideB = y2 -y1;
int sideAsqd = sideA * sideA;
int sideBsqd = sideB * sideB;
int sideCsqd = sideAsqd + sideBsqd;
double dist = sqrt(sideCsqd);
return dist;
}
And in main do this:
double res = calcDistance (x1, y1, x2, y2);
cout << "The calculated distance is "<< res << endl;

Answer 2

Given a function, say
void calcDistance (int x1, int y1, int x2, int y2)
{
//...
double dist;
//...
}
The variable dist goes out of scope at the closing brace, so not only can you not refer to it from elsewhere, it won't exist when outside the function.
If you want the value somewhere else, return it:
double calcDistance (int x1, int y1, int x2, int y2)
{
//...
double dist;
//...
return dist;
}
To use it elsewhere just capture the return:
double distance = calcDistance(1,2,3,4);
Now you have another local variable called distance that you can use.