import std;

​

struct A

{

    int i;

    this(this) { writeln("Expensive copy"); ++copyCount; }

}

​

int copyCount;

​

void main()

{

    writeln("Tuple");

    auto t1 = Tuple!(A)(A(42));

    writeln("\ntuple");

    auto t2 = tuple(A(42));

    copyCount = 0;

    writeln("\nUFCS chain");

    only(A(0), A(1), A(2))

        .filter!(a => a.i == 1)

        .takeOne

        .front;

    writeln(copyCount);

}