CASIN(3) Library Functions Manual CASIN(3)

casin casinf casinl — complex arc sine functions

#include <complex.h>

double complex casin(double complex z);
float complex casinf(float complex z);
long double complex casinl(long double complex z);

The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here and the ISO C standard is unintentional. This volume of POSIX.1-2024 defers to the ISO C standard.

These functions shall compute the complex arc sine of z, with branch cuts outside the interval [-1, +1] along the real axis.

These functions shall return the complex arc sine value, in the range of a strip mathematically unbounded along the imaginary axis and in the interval [-ℼ/2, +ℼ/2] along the real axis.

casin ( conj ( iz)), casinf ( conjf ( iz)), and casinl ( conjl ( iz)) shall return exactly the same value as conj ( casin ( iz)), conjf ( casinf ( iz)), and conjl ( casinl ( iz)), respectively, and casin ( -iz), casinf ( -iz), and casinl ( -iz) shall return exactly the same value as ( iz), -casinf ( iz), and -casinl ( iz), respectively, including for the special values of iz below.

If iz is +0 + i 0, -i (0 + i 0) shall be returned.

If iz is x + i Inf where x is positive-signed and finite, -i (+Inf + i ℼ/2) shall be returned.

If iz is x + iNaN where x is finite, -i (NaN + i NaN) shall be returned and the invalid floating-point exception may be raised.

If iz is +Inf + iy where y is positive-signed and finite, -i (+Inf + i 0) shall be returned.

If iz is +Inf + i Inf, -i (+Inf + i ℼ/4) shall be returned.

If iz is +Inf + i NaN, -i (+Inf + i NaN) shall be returned.

If iz is NaN + i 0, -i (NaN + i 0) shall be returned.

If iz is NaN + iy where y is non-zero and finite, -i (NaN + i NaN) shall be returned and the invalid floating-point exception may be raised.

If iz is NaN + i Inf, -i (±Inf + i NaN) shall be returned; the sign of the imaginary part of the result is unspecified.

If iz is NaN + i NaN, -i (NaN + i NaN) shall be returned.

No errors are defined.

None.

None.

The MXC special cases for casin () are derived from those for casinh(3) by applying the formula casin ( z) = -i casinh ( iz).

None.

casinh(3), csin(3)

XBD <complex.h>

First released in Issue 6. Derived from the ISO/IEC 9899:1999 (“ISO C99”) standard.

Austin Group Defect 1302 is applied, aligning these functions with the ISO/IEC 9899:2018 standard.

June 14, 2024 posix.fail