/C

# cargf, carg, cargl

Defined in header `<complex.h>`
`float       cargf( float complex z );`
(1) (since C99)
`double      carg( double complex z );`
(2) (since C99)
`long double cargl( long double complex z );`
(3) (since C99)
Defined in header `<tgmath.h>`
`#define carg( z )`
(4) (since C99)
1-3) Computes the argument (also called phase angle) of `z`, with a branch cut along the negative real axis.
4) Type-generic macro: if `z` has type `long double complex`, `long double imaginary`, or `long double`, `cargl` is called. If `z` has type `float complex`, `float imaginary`, or `float`, `cargf` is called. If `z` has type `double complex`, `double imaginary`, `double`, or any integer type, `carg` is called.

### Parameters

 z - complex argument

### 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 `atan2(cimag(z), creal(z))`.

### Example

```#include <stdio.h>
#include <complex.h>

int main(void)
{
double complex z1 = 1.0+0.0*I;
printf("phase angle of %.1f%+.1fi is %f\n", creal(z1), cimag(z1), carg(z1));

double complex z2 = 0.0+1.0*I;
printf("phase angle of %.1f%+.1fi is %f\n", creal(z2), cimag(z2), carg(z2));

double complex z3 = -1.0+0.0*I;
printf("phase angle of %.1f%+.1fi is %f\n", creal(z3), cimag(z3), carg(z3));

double complex z4 = conj(z3); // or CMPLX(-1, -0.0)
printf("phase angle of %.1f%+.1fi (the other side of the cut) is %f\n",
creal(z4), cimag(z4), carg(z4));
}```

Output:

```phase angle of 1.0+0.0i is 0.000000
phase angle of 0.0+1.0i is 1.570796
phase angle of -1.0+0.0i is 3.141593
phase angle of -1.0-0.0i (the other side of the cut) is -3.141593```
• C11 standard (ISO/IEC 9899:2011):
• 7.3.9.1 The carg functions (p: 196)
• 7.25 Type-generic math <tgmath.h> (p: 373-375)
• G.7 Type-generic math <tgmath.h> (p: 545)
• C99 standard (ISO/IEC 9899:1999):
• 7.3.9.1 The carg functions (p: 178)
• 7.22 Type-generic math <tgmath.h> (p: 335-337)
• G.7 Type-generic math <tgmath.h> (p: 480)

 cabscabsfcabsl (C99)(C99)(C99) computes the magnitude of a complex number (function) atan2atan2fatan2l (C99)(C99) computes arc tangent, using signs to determine quadrants (function) C++ documentation for `arg`