/+dub.sdl:

dependency "optional" version="~>0.7.1"

+/

import std.stdio;

import optional;

​

void main()

{

    // Create empty optional

    auto a = no!int;

    a.writeln; // none ([])

    ++a; // safe

    a.writeln; // 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;

​

    alias prod = a => a * a;

    some(10).map!prod.writeln; // [100]

    no!int.map!prod.writeln; // empty

    // safe access array

    auto arr = some([1, 2, 3]);

    arr[0].writeln; // [1]

    arr[300].writeln; // safe, []

    // safe dispatch of refs or optionals

    struct Data {

        int operation() { return 7; }

        Data moreData() { return this; }

    }

    Data* data = null;

    data.dispatch.moreData.operation.writeln; // safe, []

    data = new Data();

    data.dispatch.moreData.operation.writeln; // [7]

}