Replacing template class by primitive types

Question

I'm trying to write a simple compile-time dimensional analysis library. I want to create a compile option to remove everything the library does without changing the code. So essentially I made my own version of the primitive types and want to replace them by the actual primitive types if that option is selected.

This a minimal working example of the code

#include <iostream>
#include <stdint.h>

#define DEBUG
#ifdef DEBUG
    template<int lenght, int time, int mass, int charge, int temperature, int amount, int intensity> 
    struct Dimensions {
        static const int64_t LENGHT = lenght;
        static const int64_t TIME = time;
        static const int64_t MASS = mass;
        static const int64_t CHARGE = charge;
        static const int64_t TEMPERATURE = temperature;
        static const int64_t AMOUNT = amount;
        static const int64_t INTENSITY = intensity;
    };

    typedef Dimensions<  0, 0, 0, 0, 0, 0, 0 > Adimensional;
    typedef Dimensions<  1, 0, 0, 0, 0, 0, 0 > Length;
    typedef Dimensions<  0, 1, 0, 0, 0, 0, 0 > Time;

    template<typename Dims> class Int32 {
    private:
        int32_t m_value;

    public:
        inline Int32() : m_value(0) {}

        inline Int32(int32_t value) : m_value(value) {}

        inline int32_t value() {
            return m_value;
        }
    };

    template<typename Dims> 
    Int32<Dims> inline operator+(Int32<Dims> &lhs, Int32<Dims> &rhs) {
        return Int32<Dims>(lhs.value() + rhs.value());
    }

    struct Unmatched_dimensions_between_operands;

    template<typename DimsLhs, typename DimsRhs>
    Unmatched_dimensions_between_operands inline operator+(Int32<DimsLhs> &lhs, Int32<DimsRhs> &rhs);
#else
    template<typename Dims> using Int32<Dims> = std::int32_t;
#endif

int main(int argc, char* argv[]) {
    Int32<Time> a = 2;
    Int32<Time> b = 5;

    std::cout << (a + b).value() << "\n";
    return 0;
}

When I remove the #define DEBUG line I get the compile error

Error   C2988   unrecognizable template declaration/definition 59

Is there a proper way to replace any template version of Int32 in the code with a primitive type?

Answer 1

Try:

template<typename Dims> using Int32 = std::int32_t;

Also you need to define Time (and probably Adimensional and Length) somehow (doesn't matter how, as the template argument is never used).

Edit: Your programm still won't run, as your accessing a member value of Int32 which of course is not present in std::int32_t. However, I hope that puts you on the right track.