C++11 type_traits : same type if floating point, double if integral type

Question

I have a type Type and a variable tmp :

template<typename Type> myFunction()
{
    /* SOMETHING */ tmp = 0;
};

I would like to declare tmp as Type if Type is a floating-point type and as double if Type is an integral type. How to do that in C++11 ?

Answer 1

typedef typename std::conditional<
     std::is_floating_point<T>::value, 
     T,                                //if floating, ::type = T
     double                            //else,        ::type = double
>::type value_type;

value_type tmp; //declare variable

I'm assuming T can be only arithmetic type. If you want, you can use std::is_arithmetic to check that first. See other helpful type traits here:

• Type traits