multiple linked lists

[josilva00]

deleted

[MikeyBoy]

Simple:

sales_item_list isn't declared until after line 50 of the header. When the compiler encounters line 50, it hasn't yet seen any declaration of sales_item_list.

[coder777]

The solution is a forward declaration of sales_items_list:

Either

class sales_items_list; // Note
class product_list
{
...
};

or

class product_list
{
...
    void chooseProduct(unsigned int saleCode,product_list* aux, class sales_items_list* aux1); // Note: class
...
};