atanh(), atanhf(), atanhl()

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 of x.

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

Call feclearexcept(FE_ALL_EXCEPT) before calling atanh(), atanhf(), or atanhl().
On return, if fetestexcept(FE_ALL_EXCEPT) is nonzero, then an error has occurred.

Returns:

The inverse hyperbolic tangent of x.

If `x` is:	These functions return:	Errors:
±0.0	`x`	—
±1.0	Inf, with the same sign as `x`	FE_DIVBYZERO
Finite and \|`x`\| > 1	NaN	FE_INVALID
±Inf	NaN	FE_INVALID
NaN	NaN	—

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

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_ALL_EXCEPT);
    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