CACOS(3) Library Functions Manual CACOS(3)

cacos cacosf cacosl — complex arc cosine functions

#include <complex.h>

double complex cacos(double complex z);
float complex cacosf(float complex z);
long double complex cacosl(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 cosine of z, with branch cuts outside the interval [-1, +1] along the real axis.

These functions shall return the complex arc cosine value, in the range of a strip mathematically unbounded along the imaginary axis and in the interval [0, ℼ] along the real axis.

cacos ( conj ( z)), cacosf ( conjf ( z)), and cacosl ( conjl ( z)) shall return exactly the same value as conj ( cacos ( z)), conjf ( cacosf ( z)), and conjl ( cacosl ( z)), respectively, including for the special values of z below.

If z is ±0 + i 0, ℼ/2 - i 0 shall be returned.

If z is ±0 + i NaN, ℼ/2 + i NaN shall be returned.

If z is x + i Inf where x is finite, ℼ/2 - i Inf shall be returned.

If z is x + i NaN where x is non-zero and finite, NaN + i NaN shall be returned and the invalid floating-point exception may be raised.

If z is -Inf + iy where y is positive-signed and finite, ℼ - i Inf shall be returned.

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

If z is -Inf + i Inf, 3ℼ/4 - i Inf shall be returned.

If z is +Inf + i Inf, ℼ/4 - i Inf shall be returned.

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

If z is NaN + iy where y is finite, NaN + i NaN shall be returned and the invalid floating-point exception may be raised.

If z is NaN + i Inf, NaN - i Inf shall be returned.

If z is NaN + i NaN, NaN - i NaN shall be returned.

No errors are defined.

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ccos(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