Where to find standard C++17 cmath file?

Question

Where I can find original cmath or math.h files?

I need to use a comp_ellint_1(double) function in my program. It is declared in C++17 standard in Special functions.

But my compilers(I tried g++/clang++ etc.) say this.

I found out that in core files, where standard math.h and cmath are, there are no such functions declared in cmath. It looks like it is 99 standard...

Answer 1

These functions are available in gcc starting with version 7.1 and in clang starting with 3.9. You either have to upgrade your compiler, or use some other implementation (according to en.cppreference.com, you can use Boost.math

Answer 2

This works for me. You need g++ version 7 or higher and you must specify C++17 or higher.

#include <ctgmath>
#include <iostream>

int main(int argc, char *argv[]){
  double x = 0.5;
  double y = std::comp_ellint_1(x);
  std::cout << "x="<<x <<" -> y(x)="<<y <<std::endl;
  return 0;
}

Compiled and ran as follows

$ g++ --std=c++17  test.cpp -o test
$ ./test
x=0.5 -> y(x)=1.68575
$

Incidentally, in Ubuntu 18.04, the headers are in /usr/include/c++/n/tr1/ where n=7,8, or 9 (major versions of g++ that support special math functions, as of Dec 2019)