#include<numbers>

int main(){
    double x = pi;
}

on C 20 throws the error:

error: 'pi' was not declared in this scope

I'm fairly new to C , what could be wrong?

What was wrong? The compiler wasn't ready for this. I updated it and added -std=c 20 at compile time.

CodePudding user response：

The constant pi:

1. Requires C 20

2. And is defined in the std::numbers namespace.

You must verify that your compiler implements at least this part of C 20, and provide any required compilation flags for C 20 support, as well as either replace the reference to fully-qualified std::numbers::pi, or add using namespace std::numbers, or maybe a few other aliasing alternatives that you will find explained in your C textbook.

CodePudding user response：

This one should work. Tested on GCC 11.11 C 20

#include <iostream>
#include<numbers>

using namespace std::numbers;

int main(){
    double x = pi;
    
    std::cout << "The answer is " << x ;
}