carg

Retrieve the argument of a complex number, with a branch cut along the negative real axis.

Interface Definition

C interface:

float cargf(float complex x);

double carg(double complex x);

long double cargl(long double complex x);

Parameters

Parameter	Type	Description	Input/Output
x	For cargf, x is of complex single-precision floating-point type. For carg, x is of complex double-precision floating-point type. For cargl, x is of complex, long, double-precision floating-point type.	Floating-point value of the input data.	Input

Return Value

The argument y of a complex number is returned, with a branch cut along the negative real axis. y ∈ [–π, +π]

The special values are listed in the following table.

Real Part of the Input (real)	Imaginary Part of the Input (imag)	Output Value (y)
+0	+0	+0
+0	-0	-0
+0	inf	π/2
+0	-inf	–π/2
+0	SNaN	NaN
+0	–SNaN	NaN
+0	QNaN	NaN
+0	–QNaN	NaN
-0	+0	π
-0	-0	–π
-0	inf	π/2
-0	-inf	–π/2
-0	SNaN	NaN
-0	–SNaN	NaN
-0	QNaN	NaN
-0	–QNaN	NaN
inf	+0	+0
inf	-0	-0
inf	inf	π/4
inf	-inf	–π/4
inf	SNaN	NaN
inf	–SNaN	NaN
inf	QNaN	NaN
inf	–QNaN	NaN
-inf	+0	π
-inf	-0	–π
-inf	inf	3*π/4
-inf	-inf	–3*π/4
-inf	SNaN	NaN
-inf	–SNaN	NaN
-inf	QNaN	NaN
-inf	–QNaN	NaN
SNaN	+0	NaN
SNaN	-0	NaN
SNaN	inf	NaN
SNaN	-inf	NaN
SNaN	SNaN	NaN
SNaN	–SNaN	NaN
SNaN	QNaN	NaN
SNaN	–QNaN	NaN
–SNaN	+0	NaN
–SNaN	-0	NaN
–SNaN	inf	NaN
–SNaN	-inf	NaN
–SNaN	SNaN	NaN
–SNaN	–SNaN	NaN
–SNaN	QNaN	NaN
–SNaN	–QNaN	NaN
QNaN	+0	NaN
QNaN	-0	NaN
QNaN	inf	NaN
QNaN	-inf	NaN
QNaN	SNaN	NaN
QNaN	–SNaN	NaN
QNaN	QNaN	NaN
QNaN	–QNaN	NaN
–QNaN	+0	NaN
–QNaN	-0	NaN
–QNaN	inf	NaN
–QNaN	-inf	NaN
–QNaN	SNaN	NaN
–QNaN	–SNaN	NaN
–QNaN	QNaN	NaN
–QNaN	–QNaN	NaN

Dependency

C: "km.h"

Example

C interface:

    // typical usage
    double x1 = INFINITY, y1 = INFINITY;
    double x2 = -INFINITY, y2 = 0;
    double x3 = 0, y3 = -INFINITY;
    double x4 = NAN, y4 = NAN;
    double x5 = 0, y5 = 0;
    // print result
    printf("/*\n");
    printf(" * carg(%.2f + %.2f*I) = %.6f\n", x1, y1, carg(__builtin_complex(x1, y1)));
    printf(" * carg(%.2f + %.2f*I) = %.6f\n", x2, y2, carg(__builtin_complex(x2, y2)));
    printf(" * carg(%.2f + %.2f*I) = %.6f\n", x3, y3, carg(__builtin_complex(x3, y3)));
    printf(" * carg(%.2f + %.2f*I) = %.6f\n", x4, y4, carg(__builtin_complex(x4, y4)));
    printf(" * carg(%.2f + %.2f*I) = %.6f\n", x5, y5, carg(__builtin_complex(x5, y5)));
 
   /*
    * carg(inf + inf*I) = 0.785398
    * carg(-inf + 0.00*I) = 3.141593
    * carg(0.00 + -inf*I) = -1.570796
    * carg(nan + nan*I) = nan
    * carg(0.00 + 0.00*I) = 0.000000
    **/

Parent topic: Complex Functions