std::arg(std::complex) (3) Linux Manual Page

std::arg(std::complex) – std::arg(std::complex)

Synopsis

Defined in header <complex>
template< class T > (1)
T arg( const complex<T>& z );
long double arg( long double z ); (2) (since C++11)
template< class DoubleOrInteger > (3) (since C++11)
double arg( DoubleOrInteger z );
float arg( float z ); (4) (since C++11)
Calculates the phase angle (in radians) of the complex number z
(since C++11)Additional overloads are provided for float, double, long double, and all integer types, which are treated as complex numbers with zero imaginary component.

Parameters

z – complex value

Return value

If no errors occur, returns the phase angle of z in the interval [−π; π].
Errors and special cases are handled as if the function is implemented as std::atan2(std::imag(z), std::real(z)).

Example

// Run this code

#include <iostream>

#include <complex>
int main()

{
    std::complex<double> z1(1, 0);
    std::cout << "phase angle of " << z1 << " is " << std::arg(z1) << '\n';
    std::complex<double> z2(0, 1);
    std::cout << "phase angle of " << z2 << " is " << std::arg(z2) << '\n';
    std::complex<double> z3(-1, 0);
    std::cout << "phase angle of " << z3 << " is " << std::arg(z3) << '\n';
    std::complex<double> z4(-1, -0.0);
    std::cout << "phase angle of " << z4 << " (the other side of the cut) is "
              << std::arg(z4) << '\n';
}

Output:

  phase angle of (1,0) is 0
  phase angle of (0,1) is 1.5708
  phase angle of (-1,0) is 3.14159
  phase angle of (-1,-0) (the other side of the cut) is -3.14159

See also

                     returns the magnitude of a complex number
abs(std::complex) (function template)
                     constructs a complex number from magnitude and phase angle
polar (function template)
atan2
atan2f
atan2l arc tangent, using signs to determine quadrants
                     (function)
(C++11)
(C++11)
                     applies the function std::atan2 to a valarray and a value
atan2(std::valarray) (function template)