atanh.php

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<?php

namespace Complex;

if (!function_exists(__NAMESPACE__ . '\\atanh')) {
    function atanh($complex): Complex
    {
        $complex = Complex::validateComplexArgument($complex);

        if ($complex->isReal()) {
            $real = $complex->getReal();
            if ($real >= -1.0 && $real <= 1.0) {
                return new Complex(\atanh($real));
            } else {
                return new Complex(\atanh(1 / $real), (($real < 0.0) ? M_PI_2 : -1 * M_PI_2));
            }
        }

        $iComplex = clone $complex;
        $iComplex = $iComplex->invertImaginary()
            ->reverse();
        return atan($iComplex)
            ->invertReal()
            ->reverse();
    }
}