From bug-octave-request at bevo dot che dot wisc dot edu Fri Dec 19 08:35:49 2003
Subject: (-1).^.5 == NaN
From: Paul Kienzle <pkienzle at jazz dot ncnr dot nist dot gov>
To: bug-octave at bevo dot che dot wisc dot edu
Date: Fri, 19 Dec 2003 09:35:37 -0500

Debian octave-2.1.52

   octave:9>  (-1).^.5
   ans = NaN

IRIX octave-2.1.40

   octave:9>  (-1).^.5
   ans = NaN

This is arguably a libm problem rather than an Octave
problem, as the following code demonstrates:

#include <cmath>
#include <iostream>
#include <complex>

int main(int argc, char *argv[])
{
  std::cout << "real^real=" << std::pow(-1.,0.5) << std::endl;
  std::cout << "real^cplx=" << std::pow(-1.,std::complex<double>(0.5,0)) << std::endl;
  std::cout << "cplx^real=" << std::pow(std::complex<double>(-1.,0),0.5) << std::endl;
  std::cout << "cplx^cplx=" << std::pow(std::complex<double>(-1.,0),std::complex<double>(0.5,0)) << std::endl;
  return 0;
}

Debian libm:

   real^real=nan
   real^cplx=(nan,nan)
   cplx^real=(nan,0)
   cplx^cplx=(6.12303e-17,1)

IRIX libm:

  real^real=nan
  real^cplx=(nan,nan)
  cplx^real=(6.12323e-17,1)
  cplx^cplx=(6.12323e-17,1)

Paul Kienzle
pkienzle at users dot sf dot net



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