#include <iostream>
#include <thread>
#include <cstdlib>
#include <chrono>
#include <mutex>

class Stock
{
private:
    mutable std::mutex m;
    double price;
public:
    Stock(double startingPrice)
    {
        price = startingPrice;
    }
    double getPrice()
    {
        std::lock_guard<std::mutex> l(m);
        return price;
    }
    void setPrice(double Price)
    {
        std::lock_guard<std::mutex> l(m);

        price = Price;
        if(price < 0)
            price = 0.0;
    }
};

void priceRandom(Stock & stock)
{
    for(;;)
    {
        stock.setPrice(stock.getPrice() + (std::rand()%200 - 100) / 100.0);
        std::this_thread::sleep_for(std::chrono::milliseconds(1));
    }
}

int main()
{
    Stock stock(100);
    std::cout << "Hello world!\n";

    std::thread thread(priceRandom, std::ref(stock));

    for(int i = 0; i<100; i++)
    {
        std::cout << "Price of stock: " << stock.getPrice() << "\n";
        std::this_thread::sleep_for(std::chrono::milliseconds(10));
    }
    return 0;
}