Update optional.hpp

[0blu]

🍰 Pullrequest

Upgrades nonstd::optional so move semantics are used and a default constructor is not required.
With this upgrade we will also have have access to monadics.

It will perform as good as the original std::optional implementation.

Old	New
MyTestClass[0] new MyTestClass[1 <- 0] copy MyTestClass[0] dtor MyTestClass[1] The actual function was called MyTestClass[1] dtor	MyTestClass[0] new MyTestClass[1 <- 0] move MyTestClass[0] dtor MyTestClass[1] The actual function was called MyTestClass[1] dtor

Code to test

#include <iostream>
#include "nonstd/optional.hpp"

class MyTestClass final
{
public:
    MyTestClass() : m_mycount{g_counter++}
    {
        std::cout << "MyTestClass[" << m_mycount << "] new" << std::endl;
    }
    MyTestClass(MyTestClass&& other) noexcept : m_mycount{g_counter++}
    {
        std::cout << "MyTestClass[" << m_mycount << " <- " << other.m_mycount << "] move" << std::endl;
    }
    MyTestClass(MyTestClass const& other) noexcept : m_mycount{g_counter++}
    {
        std::cout << "MyTestClass[" << m_mycount << " <- " << other.m_mycount << "] copy" << std::endl;
    }
    ~MyTestClass()
    {
    std::cout << "MyTestClass[" << m_mycount << "] dtor" << std::endl;
    }

    void CallMe() const
    {
        std::cout << "MyTestClass[" << m_mycount << "] The actual function was called" << std::endl;
    }
private:
    int const m_mycount;
    static int g_counter;
};
int MyTestClass::g_counter;

nonstd::optional<MyTestClass> getAnOptionalInstance() {
    return nonstd::make_optional(MyTestClass());
}

int main()
{
    nonstd::optional<MyTestClass> maybeMyInstance = getAnOptionalInstance();
    if (maybeMyInstance)
        maybeMyInstance->CallMe();

    return 0;
}