C++ lazy evaluation with templates

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Switch passed type from template 4 answers

---

if(is_recursable<A>::value == 1)
  /* printf("1 %s", typeid(B).name()); */
  lhs.printrec();
else
  printf("0");

Until constexpr if exists you cannot do this. Reason being is that the compiler must assume that both branches are possible even if one or the other is not reachable--yeah, seems like it should be able to tell, but it's not allowed to by the language. You need to use tag dispatching or some other compile time construct.

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