std::arg(std::complex) - cppreference.com (original) (raw)
| Defined in header | ||
|---|---|---|
| template< class T > T arg( const std::complex<T>& z ); | (1) | |
| Additional overloads (since C++11) | ||
| Defined in header | ||
| (A) | ||
| float arg( float f ); double arg( double f ); long double arg( long double f ); | (until C++23) | |
| template< class FloatingPoint > FloatingPoint arg( FloatingPoint f ); | (since C++23) | |
| template< class Integer > double arg( Integer i ); | (B) |
- 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) |
|---|
[edit] Parameters
| z | - | complex value |
|---|---|---|
| f | - | floating-point value |
| i | - | integer value |
[edit] Return value
- 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
#include #include int main() { std::complex z1(1, 0); std::complex z2(0, 0); std::complex z3(0, 1); std::complex z4(-1, 0); std::complex 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