import std.algorithm : among;

import std.traits : isIntegral, isFloatingPoint;

​

mixin template Scale(alias u)

{

    auto ref opBinary(string op, this T, B)(auto ref B rhs)

        if (op.among("*", "-") && (isIntegral!B || isFloatingPoint!B))

    {

        T result = T(mixin("u" ~ op ~ "rhs"));

        return result;

    }

}

​

mixin template AddSub()

{

    auto ref opBinary(string op, this T)(auto ref T rhs)

        if (op.among("+", "-"))

    {

        T result = T(mixin("underlying" ~ op ~ "rhs.underlying"));

        return result;

    }

}

​

struct WrapInt

{

    int underlying;

    //mixin Scale!underlying;

    mixin AddSub!();

}

​

unittest {

    WrapInt a = WrapInt(5);

    WrapInt b = WrapInt(10);

​

    assert (a + b == WrapInt(15));

    //assert (a * 3 == WrapInt(15));

}

​

void main()

{

} 

​