/+dub.sdl:

dependency "optional" version="~>0.7.1"

+/

import std.stdio;

import optional;

​

void main()

{

    // Create empty optional

    auto a = no!int;

    assert(a == none);

​

    ++a; // safe;

    a - 1; // safe;

​

    // Assign and try doing the same stuff

    a = 9;

    assert(a == some(9));

​

    ++a; // some(10);

    a - 1; // some(9);

​

    // Acts like a range as well

    import std.algorithm : map;

    import std.conv : to;

​

    cast(void)some(10).map!(to!double); // [10.0]

    cast(void)no!int.map!(to!double); // empty

​

    auto r = some(1).match!((int a) => "yes", () => "no",);

    assert(r == "yes");

}