trusty (3) atanhl.3posix.gz

NAME

       atanh, atanhf, atanhl - inverse hyperbolic tangent functions

SYNOPSIS

       #include <math.h>

       double atanh(double x);
       float atanhf(float x);
       long double atanhl(long double x);

DESCRIPTION

       These functions shall compute the inverse hyperbolic tangent of their argument x.

       An   application   wishing   to   check   for  error  situations  should  set  errno  to  zero  and  call
       feclearexcept(FE_ALL_EXCEPT) before calling  these  functions.   On  return,  if  errno  is  non-zero  or
       fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has occurred.

RETURN VALUE

       Upon  successful  completion,  these  functions  shall  return  the  inverse  hyperbolic tangent of their
       argument.

       If x is ±1, a pole error shall occur, and atanh(), atanhf(), and atanhl() shall return the value  of  the
       macro  HUGE_VAL,  HUGE_VALF,  and HUGE_VALL, respectively, with the same sign as the correct value of the
       function.

       For finite |x|>1, a domain error shall occur, and    either a NaN (if supported), or   an implementation-
       defined value shall be returned.

       If x is NaN, a NaN shall be returned.

       If x is ±0, x shall be returned.

       If  x  is ±Inf, a domain error shall occur, and either a NaN (if supported), or an implementation-defined
       value shall be returned.

       If x is subnormal, a range error may occur and x should be returned.

ERRORS

       These functions shall fail if:

       Domain Error
              The x argument is finite and not in the range [-1,1],    or is ±Inf.

       If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then errno shall be set to [EDOM].
       If  the  integer  expression  (math_errhandling & MATH_ERREXCEPT) is non-zero, then the invalid floating-
       point exception shall be raised.

       Pole Error
              The x argument is ±1.

       If the integer expression (math_errhandling & MATH_ERRNO)  is  non-zero,  then  errno  shall  be  set  to
       [ERANGE].  If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, then the divide-by-
       zero floating-point exception shall be raised.

       These functions may fail if:

       Range Error
              The value of x is subnormal.

       If the integer expression (math_errhandling & MATH_ERRNO)  is  non-zero,  then  errno  shall  be  set  to
       [ERANGE].  If  the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, then the underflow
       floating-point exception shall be raised.

       The following sections are informative.

EXAMPLES

       None.

APPLICATION USAGE

       On error, the expressions (math_errhandling & MATH_ERRNO) and  (math_errhandling  &  MATH_ERREXCEPT)  are
       independent of each other, but at least one of them must be non-zero.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       feclearexcept()  , fetestexcept() , tanh() , the Base Definitions volume of IEEE Std 1003.1-2001, Section
       4.18, Treatment of Error Conditions for Mathematical Functions, <math.h>

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition,
       Standard  for  Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers,
       Inc  and  The  Open Group. In the event of any discrepancy between this version and the original IEEE and
       The Open Group Standard, the original IEEE and The Open Group  Standard  is  the  referee  document.  The
       original Standard can be obtained online at http://www.opengroup.org/unix/online.html .