Task: Fivenum
C++: #include <algorithm>
#include <iostream>
#include <ostream>
#include <vector>





template<std::size_t> struct int_ {};

template <class Tuple, size_t Pos>
std::ostream& print_tuple(std::ostream& out, const Tuple& t, int_<Pos>) {
    out << std::get< std::tuple_size<Tuple>::value - Pos >(t) << ", ";
    return print_tuple(out, t, int_<Pos - 1>());
}

template <class Tuple>
std::ostream& print_tuple(std::ostream& out, const Tuple& t, int_<1>) {
    return out << std::get<std::tuple_size<Tuple>::value - 1>(t);
}

template <class... Args>
std::ostream& operator<<(std::ostream& out, const std::tuple<Args...>& t) {
    out << '(';
    print_tuple(out, t, int_<sizeof...(Args)>());
    return out << ')';
}



template <class RI>
double median(RI beg, RI end) {
    if (beg == end) throw std::runtime_error("Range cannot be empty");
    auto len = end - beg;
    auto m = len / 2;
    if (len % 2 == 1) {
        return *(beg + m);
    }

    return (beg[m - 1] + beg[m]) / 2.0;
}

template <class C>
auto fivenum(C& c) {
    std::sort(c.begin(), c.end());

    auto cbeg = c.cbegin();
    auto cend = c.cend();

    auto len = cend - cbeg;
    auto m = len / 2;
    auto lower = (len % 2 == 1) ? m : m - 1;
    double r2 = median(cbeg, cbeg + lower + 1);
    double r3 = median(cbeg, cend);
    double r4 = median(cbeg + lower + 1, cend);

    return std::make_tuple(*cbeg, r2, r3, r4, *(cend - 1));
}

int main() {
    using namespace std;
    vector<vector<double>> cs = {
        { 15.0, 6.0, 42.0, 41.0, 7.0, 36.0, 49.0, 40.0, 39.0, 47.0, 43.0 },
        { 36.0, 40.0, 7.0, 39.0, 41.0, 15.0 },
        {
            0.14082834,  0.09748790,  1.73131507,  0.87636009, -1.95059594,  0.73438555,
           -0.03035726,  1.46675970, -0.74621349, -0.72588772,  0.63905160,  0.61501527,
           -0.98983780, -1.00447874, -0.62759469,  0.66206163,  1.04312009, -0.10305385,
            0.75775634,  0.32566578
        }
    };

    for (auto & c : cs) {
        cout << fivenum(c) << endl;
    }

    return 0;
}

VB: Option Base 1
Private Function median(tbl As Variant, lo As Integer, hi As Integer)
    Dim l As Integer: l = hi - lo + 1
    Dim m As Integer: m = lo + WorksheetFunction.Floor_Precise(l / 2)
    If l Mod 2 = 1 Then
        median = tbl(m)
    Else
        median = (tbl(m - 1) + tbl(m)) / 2
    End if 
End Function
Private Function fivenum(tbl As Variant) As Variant
    Sort tbl, UBound(tbl)
    Dim l As Integer: l = UBound(tbl)
    Dim m As Integer: m = WorksheetFunction.Floor_Precise(l / 2) + l Mod 2
    Dim r(5) As String
    r(1) = CStr(tbl(1))
    r(2) = CStr(median(tbl, 1, m))
    r(3) = CStr(median(tbl, 1, l))
    r(4) = CStr(median(tbl, m + 1, l))
    r(5) = CStr(tbl(l))
    fivenum = r
End Function
Public Sub main()
    Dim x1 As Variant, x2 As Variant, x3 As Variant
    x1 = [{15, 6, 42, 41, 7, 36, 49, 40, 39, 47, 43}]
    x2 = [{36, 40, 7, 39, 41, 15}]
    x3 = [{0.14082834, 0.09748790, 1.73131507, 0.87636009, -1.95059594, 0.73438555, -0.03035726, 1.46675970, -0.74621349, -0.72588772, 0.63905160, 0.61501527, -0.98983780, -1.00447874, -0.62759469, 0.66206163, 1.04312009, -0.10305385, 0.75775634, 0.32566578}]
    Debug.Print Join(fivenum(x1), " | ")
    Debug.Print Join(fivenum(x2), " | ")
    Debug.Print Join(fivenum(x3), " | ")
End Sub