Re: wrong result in complex pow

From: Christopher Kormanyos (e_float_at_[hidden])
Date: 2021-01-30 09:33:56

 > the pow-function pow(scalar, complex) in> boost/math/cstdfloat/cstdfloat_complex_std.hpp> get wrong result.
Thanks Gero,
Good catch. This does seem like a bug.I am on the go, but later today, I'll add thisas an issue in Git and kick off the discussionfor the fix with the colleagues.
Kind regards, Chris

    On Thursday, January 28, 2021, 12:55:59 PM GMT+1, Gero Peterhoff via Boost <boost_at_[hidden]> wrote:  
 
 Hello,
the pow-function pow(scalar, complex) in boost/math/cstdfloat/cstdfloat_complex_std.hpp get wrong result.

Current implementation:
inline complex<BOOST_CSTDFLOAT_EXTENDED_COMPLEX_FLOAT_TYPE> pow(const BOOST_CSTDFLOAT_EXTENDED_COMPLEX_FLOAT_TYPE& x,
                                                                const complex<BOOST_CSTDFLOAT_EXTENDED_COMPLEX_FLOAT_TYPE>& a)
{
  return std::exp(a * std::log(x));
}

I think that's correct:
inline complex<BOOST_CSTDFLOAT_EXTENDED_COMPLEX_FLOAT_TYPE> pow(const BOOST_CSTDFLOAT_EXTENDED_COMPLEX_FLOAT_TYPE& x,
                                                                const complex<BOOST_CSTDFLOAT_EXTENDED_COMPLEX_FLOAT_TYPE>& a)
{
  return std::exp(a * std::log(complex<BOOST_CSTDFLOAT_EXTENDED_COMPLEX_FLOAT_TYPE>(x)));
}

regards
Gero

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