c++ - Static Assert that a type A can be constructed from type B -

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I am trying to make a constant assertion for two types of A and B; Class A must be a public constructor of signature A (B & B) or A (Const B & B).

Let me tell you some type of is_constructable_from & lt; A, B & gt; : Value which evaluates for true if any public A (B & B) or A (Const B & B) or A (BB) exists.

I think this is somewhat different from promoting.

How do I get it?

Am I not left anything that will boost types of symptoms or concepts in the Czech Library?

Now I need to do a constant check that the expression aa (b) is a valid one, as the previous concept recommended by the show is less restrictive than both The solution to the cases is welcome. I have permission to use Boost.

Constructors are not members - they have no address you can take, so SFINAE It is impossible to test their presence in a direct way with .

While it is not at all with C ++ 11 you can meet with , and with C ++ 03 you can get your rollout Must do: 

  template & lt; Class A, class B = null & gt; Structure is_constructible; Template & lt; Class A, Class B & gt; Structure is_constructible {template & lt; Class U & gt; Stable u decadence (); Template & lt; Std :: size_t N & gt; Structure dummy; Template & lt; Square U & gt; Static Four Trials (Dummy & Lt; Saiff (U (Develwell & lt; B & gt; ())); *); Template & lt; Square U & gt; Stable long exam (...); Static Controlled Bull Value = Sizef (Test; & lt; a & gt; (0)) == Size (Four); }; The following is an interesting attempt, but in my understanding, it does not work well in the compiler:

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