/+dub.sdl:

dependency "optional" version="~>0.5"

+/

import std.stdio;

import optional;

​

void main()

{

    // Create empty optional

    auto a = no!int;

​

    a.writeln; // none ([])

​

    ++a; // still none

​

    // Assign and try doing the same stuff

    a = 9;

    a.writeln; // some(9)

​

    ++a;

    a.writeln; // some(10)

​

    // Acts like a range as well

    import std.algorithm : map;

    import std.conv : to;

​

    auto b = 10.some;

    auto c = no!int;

​

    alias prod = a => a * a;

    b.map!prod.writeln; // [100]

    c.map!prod.writeln; // empty

}