Question

So, one of my classes has the following overload:

DVector &operator+=(DVector const &other) {
    if (vector.size() >= other.vector.size()) throw up; // lol.

    std::for_each(other.vector.begin(); other.vector.end(), [](DVector const &pass) {
        // huh?
    });
}

So, the idea is to sum every member of both vectors (uhm, every DVector instance contains a std::vector<float> member called vector), for example:

If I had one DVector containing a vector member containing the following floats: 11.0, 23.5, 12.3, and then another one containing 14.0, 6.5, 7.7, the sum of both should lead to the first vector holding 25.0, 25.0, 25.0.

The question: is there any way to loop through both vectors and sum their members using only one iterator, assuming that the size of the vectors isn’t a problem, or am I just forced to use a for (auto x: vector.size())?

Cheers, Julian.

Answer 1

The is a std::transfom algorithm that take in two inputs and an output iterator.

I don’t know how you specific vector design is consturcted but you should be able to modify the following for your needs.

 std::transform(input1.begin(), input1.end(),  //input1
                intput2.begin(),               //input2
                input1.begin(),                //output 
     [](double a, double b){
          return a+b;
     });

You can also have a different output iterator for you operator + also well.

Here are some references

http://en.cppreference.com/w/cpp/algorithm/transform

http://www.cplusplus.com/reference/algorithm/transform/

And when you have a different output a back_inserter is your friend:

http://en.cppreference.com/w/cpp/iterator/back_inserter