[Octave-bug-tracker] [bug #59890] inf+1i*inf gives nan+1i*inf

[John W. Eaton]

Follow-up Comment #8, bug #59890 (project octave):

To create -Inf+InfI in Octave, you can use


x = complex (-Inf, Inf)


Then exp (x) will produce 0.  That is what the Fortran program is doing.

The following version is more like what Octave is doing:


      program tstexp
      double precision zero, one, inf
      complex* 16 im, cval
      zero = 0.0d0
      one = 1.0d0
      inf = one / zero
      im = cmplx (zero, one)
      cval = -inf + im*inf;
      write(6,*) cval, exp(cval)
      stop
      end


We could fix the specific case of scalar multiplication of Inf and a complex
value with zero real (or imaginary) part.  And we could use our own complex
class internally in Octave to fix more possible occurrences of these
multiplications for operations that are done directly in Octave code.  But
that wouldn't fix things like


x = [i,2,3], y = Inf(3,1), x*y


where the multiplication is handled by a BLAS function and won't use our
overloaded class definition.

    _______________________________________________________

Reply to this item at:

  <https://savannah.gnu.org/bugs/?59890>

_______________________________________________
  Message sent via Savannah
  https://savannah.gnu.org/