cargf, carg, cargl

 

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Technical Specifications

 

Numerics

Common mathematical functions

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Complex number arithmetics

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Type-generic math

 

Complex number arithmetic

Types and the imaginary constant
complex _Complex_I CMPLX	imaginary _Imaginary_I I
Manipulation
cimag creal carg	cabs conj cproj
Power and exponential functions
cexp clog	cpow csqrt
Trigonometric functions
ccos csin ctan	cacos casin catan
Hyperbolic functions
ccosh csinh ctanh	cacosh casinh catanh

 

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

Run this code

#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

References

• 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)

See also

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