Question

I thought I was doing this right but it doesn’t seem to be working. I’m basically experimenting with a queue and it works fine with one data type but now I’m trying to add multiple(in the end I want to have a int and a list of ints).

Here’s the code:

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

int main()
{
    struct product {
      int x;
      int y;
    } ;


   queue<product> q;
   q.push(100, 100);
   q.push(200, 100);
   q.push(300, 100);
   q.push(400, 100);

   cout << "Size of the queue: " << q.size() << endl;

   while (!q.empty()) {
       cout << q.front() << endl;
       q.pop();
   }

}

It works without the struct, but obviously it only accepts one variable for each item in the queue that way. Is there a way to have multiple items?

Answer 1

I think the type specified for the template type cannot be a local definition. Change to:

struct product {
  int x;
  int y;
} ;

int main()
{

As others have already stated, add a constructor to product that accepts both arguments:

struct product {
    int x;
    int y;
    product(int a_x, int a_y) : x(a_x), y(a_y) {}
};

...

q.push_back(product(100, 100));

You could also overload operator<< for outputting a product:

std::ostream& operator<<(std::ostream& a_out, const product& a_p)
{
    a_out << "product(" << a_p.x << ", " << a_p.y << ")";
    return a_out;
}

while (!q.empty()) {
    cout << q.front() << endl;
    q.pop();
}