Compiler-Enforced Semantic Types Sample Implementation (based on Bjarne Stroustrup's talk at https://youtu.be/0iWb_qi2-uI?t=19m6s)

main.cpp

    //Compiled with clang -std=c++14 -Weverything -Wno-c++98-compat main.cpp -o main

    #include <iostream>
    #include <string>

    template<int M, int K, int S>  //Meters, Kilograms, Seconds (MKS)
    struct Unit
    {
        enum { m=M, kg=K, s=S };
    };

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

    //Basic Semantic Units for MKS domain
    using Meter = Unit<1, 0, 0>;
    using Kilogram = Unit<0, 1, 0>;
    using Second = Unit<0, 0, 1>;
    using Second2 = Unit<0, 0, 2>;

    //Semantic Value Types for MKS domain
    using Time = Value<Second>;
    using Distance = Value<Meter>;
    using Mass = Value<Kilogram>;
    using Speed = Value<Unit<1, 0, -1>>; //Speed is meters/second
    using Acceleration = Value<Unit<1, 0, -2>>; //Acceleration is meters/second^2

    //Operator overloads to properly calculate units (incomplete; for demo purposes)
    Speed operator/(const Distance& lhs, const Time& rhs)
    {
        return Speed(lhs.val / rhs.val);
    }

    Acceleration operator/(const Speed& lhs, const Time& rhs)
    {
        return Acceleration(lhs.val / rhs.val);
    }

    //Define literals
    constexpr Distance operator"" _m(long double ld)
    {
        return Distance(static_cast<double>(ld));
    }

    constexpr Mass operator"" _kg(long double ld)
    {
        return Mass(static_cast<double>(ld));
    }

    constexpr Time operator"" _s(long double ld)
    {
        return Time(static_cast<double>(ld));
    }

    constexpr Acceleration operator"" _s2(long double ld)
    {
        return Acceleration(static_cast<double>(ld));
    }

    int main()
    {
        Speed sp = Distance(100)/Time(9.58); //Not bad, but units could be more convenient...
        Distance d1 = 100.0_m; //A good distance to run a race
        Speed sp1 = 100.0_m/9.58_s; //A human can run this fast
    //    Speed sp3 = 100.0/9.8_s; //Error: 100 has no unit
    //    Speed sp2 = 100.0_m/9.8_s2; //Error: speed is m/s, not m/s^2
        Acceleration ac1 = sp1/0.5_s; //Faster than any human

        return EXIT_SUCCESS;
    }