Lazy.hpp

#pragma once
#include <Optional.hpp>
template<typename T>
struct Lazy
{
    template <typename Func, typename... Args>
    Lazy(Func& f, Args && ... args)
    {
        m_func = [&f, &args...]{return f(args...); };
    }

    T& Value()
    {
        if (!m_value.IsInit())
        {
            m_value = m_func();
        }

        return *m_value;
    }

    bool IsValueCreated() const
    {
        return m_value.IsInit();
    }

private:
    std::function<T()> m_func;
    Optional<T> m_value;
};

template<class Func, typename... Args>
Lazy<typename std::result_of<Func(Args...)>::type>
    lazy(Func && fun, Args && ... args)
{
    return Lazy<typename std::result_of<Func(Args...)>::type>(std::forward<Func>(fun), std::forward<Args>(args)...);
}