c/numeric/math/atanh

@1-3@ Computes the inverse hyperbolic tangent of. @4@ Type-generic macro: If the argument has type, is called. Otherwise, if the argument has integer type or the type, is called. Otherwise, is called. If the argument is complex, then the macro invokes the corresponding complex function.

Return value
If no errors occur, the inverse hyperbolic tangent of ($tanh-1 (arg)$, or $artanh(arg)$), is returned.

If a domain error occurs, an implementation-defined value is returned (NaN where supported).

If a pole error occurs, huge_val,, or is returned (with the correct sign).

If a range error occurs due to underflow, the correct result (after rounding) is returned.

Error handling
Errors are reported as specified in.

If the argument is not on the interval $[-1, +1]$, a range error occurs.

If the argument is ±1, a pole error occurs.

If the implementation supports IEEE floating-point arithmetic (IEC 60559),
 * if the argument is ±0, it is returned unmodified
 * if the argument is ±1, ±∞ is returned and fe_divbyzero is raised.
 * if $|arg|>1$, NaN is returned and fe_invalid is raised.
 * if the argument is NaN, NaN is returned.