C++ 中数组的"expression must have pointer-to-object type"是什么？

我在有关行中评论。对我来说这没什么意义。指"表达必须具有指向对象类型的指针"。我试图使用索引随机数访问我的"项目"数组，但它错误的数组。

#include "stdafx.h"
#include <cstdio>
#include <cstdlib>
#include <iostream>
#include <windows.h>
#include <string>
#include <sstream>
#include <stdlib.h>
#include <time.h>

using namespace std;

struct product {
    double price;
} pasta, cookies, candy, chips, pop, bread, eggs;
//struct sales {
//double salepercent;
//} pastasale, cookiesale, candysale, chipsale, popsale, breadsale, eggsale;
double prices[7] = { pasta.price = 3.99, cookies.price = 4.99, candy.price = 
2.99, chips.price = 1.99, bread.price = 3.85, eggs.price = 5.99 };
//double sales[7] = {pastasale.salepercent = 0.30, cookiesale.salepercent = 
0.30, chipsale.salepercent = 0.30, popsale.salepercent = 0.30, 
breadsale.salepercent = 0.30, eggsale.salepercent = 0.30}
double costumer_cart[7] = {};
double subtotal = 0;
double total = 0;
double fillcart(double cart[], double items)
{
    srand(time(NULL));
    for (int i = 0; i < 8; i++)
    {
        cart[i] = items[rand() % 8]; //EXPRESSION MUST HAVE POINTER-TO-
OBJECT TYPE on "items[rand() % 8]"
    }
    cout << "Cart: " << cart;
}

int main()
{
    double fillcart(double costumer_cart, double prices);
    system("PAUSE");
    return 0;
}