c++ template check type validation

Question

for example,

enum tr {z, u};

template<tr T>
class test 
{
      assert(T is z or u);//how can I add assertions in this field?
};

in the comment how can I add code to assert the template T should only be z or u?

Answer 1

This can be done using static_assert as @πάντα-ῥεῖ already pointed out:

enum tr {z, u, bar};

template<tr T>
class test 
{
      static_assert(T==z||T==u, "T must be z or u");
};

int main() 
{
    test<z> t_valid; 
    test<bar> t_fails; // compilation fails
    return 0;
}

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