crtp, C++ (clang) - rextester

Language: Layout:

//clang 3.8.0

#include <iostream>

template<typename T, std::size_t N, template<typename,std::size_t> class B >
struct Pixel
{
    B<T,N> *crtp = static_cast<B<T,N>*>(this);
    
    T& operator[](std::size_t x)
    {
        return crtp->ch[x];
    }
    
    Pixel& operator = (const Pixel &t)
    {
        crtp->ch[0] = t.crtp->ch[0];
        crtp->ch[1] = t.crtp->ch[1];
        crtp->ch[2] = t.crtp->ch[2];
        return *crtp;
    }
    
    B<T,N> operator + (const B<T,N> &t)
    {
        B<T,N> tmp;
        
        tmp[0] = crtp->ch[0] + t.crtp->ch[0];
        tmp[1] = crtp->ch[1] + t.crtp->ch[1];
        tmp[2] = crtp->ch[2] + t.crtp->ch[2];
        
        return tmp;
    }
};

template<typename T, std::size_t N=3>
struct PixelBGR : Pixel<T, N, PixelBGR>
{
    union
    {
        struct
        {
            T r;
            T g;
            T b;
        };
        T ch[3];
    };
};

int main()
{
    PixelBGR<int> p;
    
    p.r = 25;
    p.g = 14;
    p.b = 58;
    
    std::cout<< p[0] <<" , "<<p[1]<<" , "<<p[2] <<std::endl;
    
    PixelBGR<int> q;
    q = p;
    std::cout<< q[0] <<" , "<<q[1]<<" , "<<q[2] <<std::endl;
    
    PixelBGR<int> res;
    res = q + p;
    std::cout<< res.r <<" , "<<res.g<<" , "<<res.b <<std::endl;
}

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Compilation time: 0.62 sec, absolute running time: 0.07 sec, cpu time: 0.01 sec, memory peak: 3 Mb, absolute service time: 0,7 sec