Suppose I have the following code:

enum class Type
{
    Type32,
    Type64
};

template<Type T>
class MyClass
{
public:
    using MyType = typename std::conditional<T == Type::Type32, uint32_t, uint64_t>::type;
    
    MyType getSum()
    {
        MyType sum = 0;
        for(size_t i = 0;i < sizeof(arr);i ++)
        {
            sum += arr[i];
        }
        return sum;
    }

 private:
     //MyType arr[4] = { 0x1234, 0x5678, 0x9ABC, 0xDEF0 }; // for Type::Type32
     //MyType arr[2] = { 0x12345678, 0x9ABCDE }; // for Type::Type64
};

I try to initialize a class variable depends on the template type with the same name but different type and value. How can I do that? I probably looking for a solution that works in c++11.

>Solution :

Here is a simple way:

#include <array>
#include <cstdint>
#include <type_traits>

enum class Type { Type32, Type64 };

template <Type>
struct As128Bits;

template <>
struct As128Bits<Type::Type32> {
    using Integer = std::uint32_t;

    std::array<Integer, 4> data{0x1234, 0x5678, 0x9ABC, 0xDEF0};
};

template <>
struct As128Bits<Type::Type64> {
    using Integer = std::uint64_t;

    std::array<Integer, 2> data{0x12345678, 0x9ABCDE};
};

template <Type T>
struct MyClass : private As128Bits<T> {
    using Integer = typename As128Bits<T>::Integer;
    using As128Bits<T>::data;

    Integer getSum() {
        Integer sum = 0;
        for (auto const val : data) {
            sum += val;
        }
        return sum;
    }
};