I think you need to enclose your code block in triple back quotes to make it render properly in markdown. I've tried to fix it up a bit.

template <typename T, const int length=5> 
class vector {  
  public:  
    T v[length];  
    vector operator +(const vector &obj) {  
        vector tmp;  
        for(int i = 0; i < length; i++)  
            tmp.v[i] = v[i] + obj.v[i];  
        return tmp;  
        /* This method below only works if length is a fixed size return  
            {v[0] + obj.v[0], v[1] + obj.v[1], v[2] + obj.v[2], v[3] + obj.v[3], v[4] + obj.v[4]};*/ 
    } 
};  

int main() {  
    vector<int> a={1,2,3,4,5}; vector<int> b={1,2,3,4,5};  

    auto c = a + b;  

    std::cout << "(int) ";  
    for(int i = 0; i < 5; i++)  
        std::cout << c.v[i] << " ";  
    std::cout << std::endl;  
}