std::arg(std::complex)

C++

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std::complex

Member functions
complex::complex
complex::operator=
complex::real
complex::imag
complex::operator+=complex::operator-=complex::operator*=complex::operator/=
Non-member functions
operator+operator- operator+operator-operator*operator/ operator==operator!= operator<<operator>>	real imag abs arg norm conj proj (C++11) polar operator""ioperator""ifoperator""il (C++14)(C++14)(C++14)
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exp
log
log10
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pow
sqrt
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sin cos tan	asin (C++11) acos (C++11) atan (C++11)
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sinh cosh tanh	asinh (C++11) acosh (C++11) atanh (C++11)

Defined in header <complex>
template< class T > T arg( const complex<T>& z );	(1)
long double arg( long double z );	(2)	(since C++11)
template< class DoubleOrInteger > double arg( DoubleOrInteger z );	(3)	(since C++11)
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 [; ].

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

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