&gt; I am pretty lenient, and would go for anything that resembles a compiler-enforced tagged union<p><a href="http:&#x2F;&#x2F;www.boost.org&#x2F;doc&#x2F;libs&#x2F;1_60_0&#x2F;doc&#x2F;html&#x2F;variant.html" rel="nofollow">http:&#x2F;&#x2F;www.boost.org&#x2F;doc&#x2F;libs&#x2F;1_60_0&#x2F;doc&#x2F;html&#x2F;variant.html</a> ??? (and I think it&#x27;s supposed to be coming in c++17)