void main()

{

    import core.stdc.math : sin;

    import core.thread;

    import std.stdio : write, writeln, writef, writefln;

​

    class DerivedThread : Thread

    {

        double d;

        this()

        {

            super(&run);

        }

​

        this(double a)

        {

            super(&run);

            this.d = sin(a);

            writeln(d);

            this.getD();

        }

​

    private:

        auto setD(double d)

        {

            this.d = d;

            return this;

        }

​

        double getD()

        {

            writeln(d);

            return d;

        }

​

        void run()

        {

            // Derived thread running.

        }

    }

​

    // create and start instances of each type

    auto derived = new DerivedThread(22);

    derived.start(); // start always returns Thread, not your DerivedThread - you should cast to get DerivedThread here

    derived.setD(11).getD();

}