cxx

First of all, great library!

I am having some confusion in understanding the role of values_first2 in set_difference_by_key as mentioned here.

In general terms, the result of set difference D = A - B will not contain values from B therefore values_first2 can never be part of D. So `val

Expected Behavior

I can pass std::vector<int32_t>, but the the c++ library I want to use uses int, not int32_t

std::vector<int> build_array() {
    auto values = std::vector<int> {1,2,3,4,5};
    for (auto& v: values) v = v * 2;
    return values;
}

Not sure how to get around this since I can't impl VectorElement for c_int due to the orphan rule? There must b

Please note that this function has been deprecated in 2011