catan(), catanf(), catanl()

Updated: April 19, 2023

Compute the complex arc tangent


#include <complex.h>

double complex catan( double complex z );

float complex catanf( float complex z );

long double complex catanl( long double complex z );


The value that you want to get the complex arc tangent of.


The general-purpose math library.
(QNX Neutrino 7.1 or later) A library that optimizes the code for ARMv8.2 chips that have Scalable Vector Extension hardware.

Your system requirements will determine how you should work with these libraries:

Note: Compile your program with the -fno-builtin option to prevent the compiler from using a built-in version of the function.


These functions compute the complex arc tangent of z, with branch cuts outside the interval [−i,+i] along the imaginary axis.

To check for error situations, use feclearexcept() and fetestexcept(). For example:


The complex arc tangent of z, in the range of a strip unbounded along the imaginary axis and in the interval [−π/2; +π/2] along the real axis.

Errors and special cases are handled as if the operation were implemented as -i * catanh(i * z).

These functions raise FE_INEXACT if the FPU reports that the result can't be exactly represented as a floating-point number.


C11, POSIX 1003.1

Cancellation point No
Interrupt handler Yes
Signal handler Yes
Thread Yes