CATAN(3) Library Functions Manual CATAN(3)

catan catanf catanl — complex arc tangent functions

#include <complex.h>

double complex catan(double complex z);
float complex catanf(float complex z);
long double complex catanl(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 tangent of z, with branch cuts outside the interval [- i, + i] along the imaginary axis.

These functions shall return the complex arc tangent 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.

catan ( conj ( iz)), catanf ( conjf ( iz)), and catanl ( conjl ( iz)) shall return exactly the same value as conj ( catan ( iz)), conjf ( catanf ( iz)), and conjl ( catanl ( iz)), respectively, and catan ( -iz), catanf ( -iz), and catanl ( -iz) shall return exactly the same value as ( iz), -catanf ( iz), and -catanl ( 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 +0 + i NaN, -i (+0 + i NaN) shall be returned.

If iz is +1 + i 0, -i (+Inf + i 0) shall be returned and the divide-by-zero floating-point exception shall be raised.

If iz is x + i Inf where x is positive-signed and finite, -i (+0 + i ℼ/2) shall be returned.

If iz is x + i NaN where x is non-zero and 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 (+0 + i ℼ/2) shall be returned.

If iz is +Inf + i Inf, -i (+0 + i ℼ/2) shall be returned.

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

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

If iz is NaN + i Inf, -i (±0 + i ℼ/2) 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 catan () are derived from those for catanh(3) by applying the formula catan ( z) = -i catanh ( iz).

None.

catanh(3), ctan(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