std::arg(std::complex)
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std::complex
(until C++20)
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(C++26)
(C++26)
Defined in header
<complex>
template< class T >
T arg( const std::complex <T>& z );
(1)
T arg( const std::complex <T>& z );
Additional overloads (since C++11)
Defined in header
<complex>
(A)
float arg( float f );
(until C++23)
double arg( double f );
template< class FloatingPoint >
(since C++23)
FloatingPoint
template< class Integer >
double arg( Integer i );
(B)
double arg( Integer i );
1) Calculates the phase angle (in radians) of the complex number z.
A,B) Additional overloads are provided for all integer and floating-point types, which are treated as complex numbers with zero imaginary component.
(since C++11)Contents
[edit] Parameters
z
-
complex value
f
-
floating-point value
i
-
integer value
[edit] Return value
1) std::atan2 (std::imag (z), std::real (z)). If no errors occur, this is the phase angle of z in the interval [−π; π].
A) Zero if f is positive or +0, π if f is negative or -0, NaN otherwise.
B) Zero if i is non-negative, π if it is negative.
[edit] Notes
The additional overloads are not required to be provided exactly as (A,B). They only need to be sufficient to ensure that for their argument num:
- If num has a standard(until C++23) floating-point type
T, then std::arg(num) has the same effect as std::arg(std::complex <T>(num)). - Otherwise, if num has an integer type, then std::arg(num) has the same effect as std::arg(std::complex <double>(num)).
[edit] Example
Run this code
#include <complex> #include <iostream> int main() { std::complex <double> z1(1, 0); std::complex <double> z2(0, 0); std::complex <double> z3(0, 1); std::complex <double> z4(-1, 0); std::complex <double> z5(-1, -0.0); double f = 1.; int i = -1; std::cout << "phase angle of " << z1 << " is " << std::arg(z1) << '\n' << "phase angle of " << z2 << " is " << std::arg(z2) << '\n' << "phase angle of " << z3 << " is " << std::arg(z3) << '\n' << "phase angle of " << z4 << " is " << std::arg(z4) << '\n' << "phase angle of " << z5 << " is " << std::arg(z5) << " " "(the other side of the cut)\n" << "phase angle of " << f << " is " << std::arg(f) << '\n' << "phase angle of " << i << " is " << std::arg(i) << '\n'; }
Output:
phase angle of (1,0) is 0 phase angle of (0,0) is 0 phase angle of (0,1) is 1.5708 phase angle of (-1,0) is 3.14159 phase angle of (-1,-0) is -3.14159 (the other side of the cut) phase angle of 1 is 0 phase angle of -1 is 3.14159
[edit] See also
C documentation for carg