I am trying to ask the user if he wants to go again on my c++ program

Question

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

void selection()
{
cout << "Press 1 to find the area of a Triangle" << endl;
cout << "Press 2 to find the area of a Square" << endl;
cout << "Press 3 to find the area of a Rectangle" << endl;
cout << "Press 4 to find the area of a Circle" << endl;
}

int main()
{
selection();
int select;
const double pi = 3.14159265359;
double base;
double height;
double side;
double radius;
double length;
double width;
double answer;
char a;

cout << endl;
cin >> select;

if (select == 1)
{
cout << endl;
cout << "Enter the base" << endl;
cin >> base;
cout << endl;
cout << "Enter the height" << endl;
cin >> height;
cout << endl;

answer = base * height / 2;

cout << "The area of the triangle is " << answer << endl;
}

else if (select == 2)
{
cout << endl;
cout << "Enter the side length" << endl;
cin >> side;
cout << endl;

answer = pow(side , 2);

cout << "The area of the square is " << answer << endl;
}

else if (select == 3)
{
cout << endl;
cout << "Enter the length" << endl;
cin >> length;
cout << endl;
cout << "Enter the width" << endl;
cin >> width;
cout << endl;

answer = length * width;

cout << "The area of the rectangle is " << answer << endl;
}

else if (select == 4)
{
cout << endl;
cout << "Enter the radius" << endl;
cin >> radius;
cout << endl;

answer = pi * pow(radius , 2);

cout << "The area of the circle is " << answer << endl;
}

while (a == 'y'||'Y')
{
cout << "Do you want to try again? [y/n] " << endl;
cin >> a;
selection();
}

cout << "The End" << endl;

return 0;
}

I tried to use a while loop to ask if the user wanted to play again but when the user enters in 'n

Answer 1

char a = 'y';

while (a == 'y')
{
// your entire program

cout << "Do you want to restart the program? (y/n)";
cin >> y;
// some input validation 'round here
}

Answer 2

do
{
selection();
// process user input
// ask user if she wants to have another go
} while (a == 'y' || a == 'Y')

Answer 3

So you want to start your program all over again, you can make a label like start: and put a goto start;.

Answer 4

Vazgen is right.
However, using label and goto isn't consider as good programming. The code can quickly become impossible to read and understand.
You can use a 'do ... while' loop. Here are the syntax :

Label:
int main(){
label beginning :
int x=0;
++x;
goto beginning ; // This code will run again and again.
}

Do ... while :
int main(){
string answer;
do{
int x=0;
++x;
cout<<"Do you want to run the code adain ? ";
cin>>answer;
} while(answer!="no")
}

Answer 5

Another, thing, I saw that you've finished the C++ course.
You should use objects in your code and 'switch ... case' statement.
If you don't know about object, try to read articles, other courses about it.