Access to maths special functions c++17

Hi all,

I have been trying lately to use some specific functions that are in the C++17 standard. However with the clang that ships with xcode 10.2, I cannot find those functions. They are however included in clang 6.0 on linux. Is there any reason I don't find it on a mac ?

The example is that one (from here: https://en.cppreference.com/w/cpp/numeric/special_math/legendre) :

#include <cmath>

#include <iostream>

double P3(double x) { return 0.5*(5*std::pow(x,3) - 3*x); }

double P4(double x) { return 0.125*(35*std::pow(x,4)-30*x*x+3); }

int main()

{

// spot-checks

std::cout << std::legendre(3, 0.25) << '=' << P3(0.25) << '\n'

<< std::legendre(4, 0.25) << '=' << P4(0.25) << '\n';

}

Compiled with clang++ -std=c++17 test.cxx . Any help or info would be appreciated

Thanks