C ++的两个函数除一行外都相同

Question

I dont want to duplicate my code, but I have 2 functions which do the same except 1 line. I do want separate functions that will call a private function, that might be a template and will solve my duplicate code problem.

double EuclideanDistance::calculateDistance(const Point &p1, const Point &p2) const
{
    if (p1.getDimension()!=p2.getDimension())
        return 0;
    double sum = 0.0;
    for( size_t i = 0; i < p1.getDimension(); i++)
    {
        sum += pow( p1[i] - p2[i], 2.0);
    }
    return sqrt(sum);
}

double EuclideanDistance::calculateWeightedDistance(const Point &p1, const Point &p2, const double *weights) const
{
    if (p1.getDimension()!=p2.getDimension())
        return 0;
    double sum = 0.0;
    for( size_t i = 0; i < p1.getDimension(); i++)
    {
        sum += pow( ((p1[i] - p2[i])*weights[i]), 2.0);//here is the difference
    }
    return sqrt(sum);
}

what do you suggest?

Answer 1

Implement only calculateWeightedDistance fully. and for calculateDistance call calculateWeightedDistance with weight 1.0

Answer 2

What about the following? If you invoke the function with the third parameter nullptr , then the behaviour of the first version is executed.

double EuclideanDistance::calculateWeightedDistance(const Point& p1, const Point& p2, const double* weights) const {
    if (p1.getDimension()!=p2.getDimension())
        return 0;

    double sum = 0.0;
    for( size_t i = 0; i < p1.getDimension(); i++)
    {
        const auto distance_d = (p1[i] - p2[i]) * 
                                (weights != nullptr ? weights[i] : 1.0);
        sum += pow(distance_d, 2.0);
    }
    return sqrt(sum);
}

Answer 3

You may factorize this way:

template <typename F, typename Ts...>
double calculateDistanceImpl(F&& f, const Point &p1, const Point &p2, Ts&&... args)
{
    if (p1.getDimension()!=p2.getDimension())
        return 0;

    double sum = 0.0;
    for( size_t i = 0; i != p1.getDimension(); i++)
    {
        sum += f(p1[i], p2[i], args[i]...);
    }
    return sqrt(sum);
}


double EuclideanDistance::calculateDistance(const Point &p1, const Point &p2) const
{
    return calculateDistanceImpl(
        [](auto&& p1, auto&& p2){ return pow(p1 - p2, 2.0);},
        p1, p2);
}

double EuclideanDistance::calculateWeightedDistance(const Point &p1,
                                                    const Point &p2,
                                                    const double *weights) const
{
    return calculateDistanceImpl(
        [](auto&& p1, auto&& p2, double weight){ return pow((p1 - p2) * weight, 2);},
        p1, p2, weights);
}