How to make a conditional typedef in C++

Question

I am trying to do something like this:

#include 
#include 

typedef int Integer;

#if sizeof(Integer) <= 4
    typedef std::         


        

Answer 1

Using std::conditional you can do it like so:

using Engine = std::conditional::type;

If you want to do a typedef, you can do that too.

typedef std::conditional::type Engine