constexpr and std::function crap

constexpr_crap.cc

#include <iostream>
#include <functional>

enum Dir { H, V };

template<Dir d>
void call(double x, double y) {
    std::function<double(double, double)> f;
    if constexpr (d == H) {
        f = [](double x, double y) -> double {
            return x * y;
        };
    } else {
        f = [](double x, double y) -> double {
            return x * y * 10;
        };
    }

    std::cout << f(x, y) << '\n';
}

void call1() {
    int n = 10;
    std::function<bool()> f;
    f = [&n]() -> bool {
        return n > 15;
    };
    std::cout << f() << '\n';
    n += 6;
    std::cout << f() << '\n';
}

int main() {
    call<V>(5, 5);
    call1();
}