c/numeric/math/acosh

@1-3@ Computes the inverse hyperbolic cosine 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 cosine of ($cosh-1 (arg)$, or $arcosh(arg)$) on the interval $[0, +∞]$, is returned.

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

Error handling
Errors are reported as specified in.

If the argument is less than 1, a domain error occurs.

If the implementation supports IEEE floating-point arithmetic (IEC 60559),
 * if the argument is less than 1, fe_invalid is raised an NaN is returned
 * if the argument is 1, +0 is returned
 * if the argument is +∞, +∞ is returned
 * if the argument is NaN, NaN is returned.