How can I create a new primitive type using C++11 style strong typedefs?

Question

I\'m trying to emulate in C++ a distinct type from the Nim programming language. The following example won\'t compile in Nim because the compiler catches the variables

Answer 1

There are several ways to solve this, but since I was looking for a fix to Bjarne's code in the presentation slides, I'm accepting this answer which @robson3.14 left in comments to the question:

#include 

template struct Unit { // a unit in the MKS system
    enum { m=M, kg=K, s=S };
};

template // a magnitude with a unit
struct Value {
    double val; // the magnitude
    // construct a Value from a double
    constexpr explicit Value(double d) : val(d) {} 
};

using Meter = Unit<1,0,0>; // unit: meter
using Second = Unit<0,0,1>; // unit: sec
using Speed = Value>; // meters/second type

// a f-p literal suffixed by ‘_s’
constexpr Value operator "" _s(long double d)
{
    return Value (d);
}
// a f-p literal suffixed by ‘_m’
constexpr Value operator "" _m(long double d)
{
    return Value (d);
}
// an integral literal suffixed by ‘_m’
constexpr Value operator "" _m(unsigned long long d)
{
    return Value (d);
}

template
Value> operator / (Value> a, Value> b)
{
    return Value>(a.val / b.val);
}

int main()
{
    Speed sp1 = 100_m / 9.8_s;
    std::cout << sp1.val;
}