may_be_usage_example.cpp

#include "may_be.hpp"
#include <iostream>

struct Point { //òèï,  íàä êîòîðûì ìû áóäåì ýêñïåðåìåíòèðîâàòü.
    float x, y;
    Point(float x, float y): x(x), y(y) {}
    Point(): x(0), y(0) {}
};

MayBe<Point> f1() {
  return MayBeEmpty; //âåðíóòü ïóñòîòó.
}

MayBe<Point> f2() {
  return MayBeDefault; //âåðíóòü îáúåêò, èíèöèàëèçèðîâàííûé ïî óìîë÷àíèþ
}

MayBe<int> f3() {
  return CreateMayBe(7); //âåðíóòü êîíêðåòíîå çíà÷åíèå.
}

template <int i> struct X {
    char a[i];
};

int main() {
    {
        MayBe<Point> point;
        //èíèöèàëèçàöèÿ ñ ïàðàìåòðàìè.
        if (true)
          MAYBE_INIT(point, Point(1, 2));
    }

    {
        MayBe<Point> point;
        //Èíèöèàëèçàöèÿ ïî óìîë÷àíèþ:
        if (true)
          point.ResetDefault();
    } 

    //Èíèöèàëèçàöèÿ êîïèðîâàíèåì ñóùåñòâóþùåãî îáúåêòà:
    Point existing(3,4);
    MayBe<Point> point = CreateMayBe(existing);
      
    //èñïîëüçîâàíèå:
    if (Point *p = point.Get()) //ïîëó÷èòü óêàçàòåëü, âîçìîæíî NULL
        std::cout << p->x;

    if (point)
        std::cout << point->x;
    std::cout << std::endl;
   
    std::cout << sizeof(MayBe<bool>) << ' ' << sizeof(MayBe<short>) << ' ' << sizeof(MayBe<float>) << ' ' << sizeof(MayBe<double>) << '\n';
}