atanh(), atanhf(), atanhl()

Compute an inverse hyperbolic tangent

Synopsis:

#include <math.h>

double atanh( double x );

float atanhf( float x );

long double atanhl( long double x );

Arguments:

x
The value for which you want to compute the inverse hyperbolic tangent.

Library:

libm

Use the -l m option to qcc to link against this library.

Description:

These functions compute the inverse hyperbolic tangent (in radians) of x.

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

Returns:

The inverse hyperbolic tangent of x.

If x is: These functions return:
±1 HUGE_VAL, HUGE_VALF, and HUGE_VALL, respectively, with the same sign as the correct value of the function, and a pole error occurs
finite and |x| > 1 NaN, and a domain error occurs
NaN NaN
±0 x
±Inf NaN, and a domain error occurs
Subnormal x, and a range error occurs

Errors:

FE_DIVBYZERO
The x argument is ±1.
FE_INVALID
The absolute value of x argument is greater than 1.
FE_UNDERFLOW
The value of x is subnormal.

Examples:

#include <stdio.h>
#include <math.h>
#include <fenv.h>
#include <stdlib.h>

int main( void )
{
    int except_flags;

    feclearexcept(FE_ALL_EXCEPT);

    printf( "%f\n", atanh( 0.5 ) );

    except_flags = fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW);
    if(except_flags) {
        /* An error occurred; handle it appropriately. */
    }

    return EXIT_SUCCESS;
}

produces the output:

0.549306

Classification:

ANSI, POSIX 1003.1

Safety:  
Cancellation point No
Interrupt handler No
Signal handler No
Thread Yes