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);
[CX] 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.
[MXC] 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 -casin(iz), -casinf(iz), and -casinl(iz), respectively, including for the special values of iz below.
If iz is +0 + i0, -i (0 + i0) shall be returned.
If iz is x + iInf where x is positive-signed and finite, -i (+Inf + iℼ/2) shall be returned.
If iz is x + iNaN where x is finite, -i (NaN + iNaN) 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 + i0) shall be returned.
If iz is +Inf + iInf, -i (+Inf + iℼ/4) shall be returned.
If iz is +Inf + iNaN, -i (+Inf + iNaN) shall be returned.
If iz is NaN + i0, -i (NaN + i0) shall be returned.
If iz is NaN + iy where y is non-zero and finite, -i (NaN + iNaN) shall be returned and the invalid floating-point exception may be raised.
If iz is NaN + iInf, -i (±Inf + iNaN) shall be returned; the sign of the imaginary part of the result is unspecified.
If iz is NaN + iNaN, -i (NaN + iNaN) shall be returned.
No errors are defined.
None.
None.
The MXC special cases for casin() are derived from those for casinh() by applying the formula casin(z) = -i casinh(iz).
None.
XBD <complex.h>
First released in Issue 6. Derived from the ISO/IEC 9899:1999 standard.
Austin Group Defect 1302 is applied, aligning these functions with the ISO/IEC 9899:2018 standard.
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