#include <optional>
#include <stdio.h>
#include <utility>
#include <vector>
#include <iostream>
using namespace std;

#define T printf("%s [%d]\n", __PRETTY_FUNCTION__, val)

struct foo {
    foo(int x = 0) : val(x) {
        T;
    }
    ~foo() {
        T;
    }
    void print() const {
        cout << "foo{" << val << "}\n";
    }

int val;
};

std::optional<foo> find(std::vector<optional<foo>> const &v) {
    if (v.size() > 0) return v[0];
    else std::nullopt;
}


int main() {
    std::vector<optional<foo>> v(5);
    v[0] = optional<foo>(4);
    auto f = find(v);
    if (f) printf("found\n");
    else   printf("not found\n");
}