STL/ranges algorithm to calculate weighted average

Question

Assume I have a vector of grades, where the grade is

struct Grade{
   const int grade;
   const int ECTS; // weight
};

Is there a STL/range-v3 algorithm/algorithms that enable me to do this?

I know I could do it with std:: accumulate with some fancy type as an accumulator(that remembers the sum of weights), but I am looking for a simpler alternative if one exists.

Answer 1

With range-v3, it might be:

auto average = ranges::inner_product(grades, grades, 0, {}, {}, &Grade::grade, &Grade::ECTS)
        / double(ranges::accumulate(grades, 0, {}, &Grade::ECTS));

Demo

Answer 2

The Grade type itself is fancy enough to act as the accumulator type.

auto [grade_sum, ects] = std::accumulate(
    grages.begin(), grades.end(), Grade {0,0}, 
    [] (Grade acc, Grade g) -> Grade {
        return { g.grade*g.ECTS + acc.grade,
                 g.ECTS         + acc.ECTS  };
});
// auto average_grade = grade_sum/ects;

C++17 structured binding can be replaced by std::tie if necessary.