Problem with loop.

I'm trying to code a basic calculator.
I'm not sure what I've done wrong with this code; could someone please help?
Thanks

Code:

#include <iostream>

using namespace std;

float add( float x, float y )
{
      return x + y;
}

float subtract( float x, float y )
{
      return x - y;
}

float multiply( float x, float y )
{
      return x * y;
}

float divide( float x, float y )
{
      return x / y;
}

int main()
{
    int s, x, y, l;
    l = 0;
    while ( l = 0 )
    {
          cout<<"What would you like to do?\n\n";
          cout<<"1. Add, 2. Subtract, 3. Multiply, 4. Divide\n";
          cin>> s;
          cin.ignore();
          if ( s == 1 )
          {
               cout<<"\nYou would like to add.\n\n";
               cout<<"Enter two numbers.\n";
               cin>> x >> y;
               cin.ignore();
               cout<<"\nAnswer... "<< add( x, y ) <<"\n";
               l++;
          }
          else if ( s == 2 )
          {
               cout<<"\nYou would like to subtract.\n\n";
               cout<<"Enter two numbers.\n";
               cin>> x >> y;
               cin.ignore();
               cout<<"\nAnswer... "<< subtract( x, y ) <<"\n";
               l++;
          }
          else if ( s == 3 )
          {
               cout<<"\nYou would like to multiply.\n\n";
               cout<<"Enter two numbers.\n";
               cin>> x >> y;
               cin.ignore();
               cout<<"\nAnswer... "<< multiply( x, y ) <<"\n";
               l++;
          }
          else if ( s == 4 )
          {
               cout<<"\nYou would like to divide.\n\n";
               cout<<"Enter two numbers.\n";
               cin>> x >> y;
               cin.ignore();
               cout<<"\nAnswer... "<< divide( x, y ) <<"\n";
               l++;
          }
          else
          {
               cout<<"\nInvalid selection.\n\n";
          }
          cin.get();
    }
}

What does your while loop actually do?

Compare your use of = and ==

I see my error.
Thanks for your quick reply.