Failure of __pow__ in RDF for noninteger powers of zero

[sagetrac-kbaker]

Positive noninteger powers of RDF(0) give nan rather than zero:

  sage: RDF(0)^.5
  nan

  sage: RDF(0)^(1/2)
  nan

In contrast, noninteger powers of CDF(0) have the correct value:

  sage: CDF(0)^.5
  0

  sage: CDF(0)^(1/2)
  0

Component: basic arithmetic

Keywords: RDF, pow, zero

Issue created by migration from https://trac.sagemath.org/ticket/5782

[sagetrac-mabshoff]

comment:2

Hmm, we have some trivial doctest failures:

sage -t -long "devel/sage/sage/rings/real_double.pyx"       
**********************************************************************
File "/scratch/mabshoff/sage-3.4.1.rc3/devel/sage/sage/rings/real_double.pyx", line 1543:
    sage: RDF(0)^.5
Expected:
    0
Got:
    0.0
**********************************************************************
File "/scratch/mabshoff/sage-3.4.1.rc3/devel/sage/sage/rings/real_double.pyx", line 1545:
    sage: RDF(0)^(1/2)
Expected:
    0
Got:
    0.0
**********************************************************************

I think other than that this is good to go.

Cheers,

Michael

[robertwb]

Attachment: 5782-rdf-pow.patch.gz

[robertwb]

comment:3

Doh! Patch updated.

[sagetrac-mabshoff]

comment:4

Second patch looks good to me. Positive review. It also passes doctests :)

Cheers,

Michael

[sagetrac-mabshoff]

comment:5

Merged in Sage 3.4.1.rc3.

Cheers,

Michael

[jasongrout]

comment:6

Does this fix #5785?

[sagetrac-mabshoff]

comment:7

Replying to @jasongrout:

Does this fix #5785?

Yes.

Cheers,

Michael