either

[Andrei Alexandrescu]

I wrote a simple helper, in spirit with some recent discussions:
// either
struct Either(Ts...)
{
    Tuple!Ts data_;
    bool opEquals(E)(E e)
    {
        foreach (i, T; Ts)
        {
            if (data_[i] == e) return true;
        }
        return false;
    }
}

auto either(Ts...)(Ts args)
{
    return Either!Ts(tuple(args));
}

unittest
{
    assert(1 == either(1, 2, 3));
    assert(4 != either(1, 2, 3));
    assert("abac" != either("aasd", "s"));
    assert("abac" == either("aasd", "abac", "s"));
}

Turns out this is very useful in a variety of algorithms. I just don't 
know where in std this helper belongs! Any ideas?


Andrei