Corrections to infinities returned by mpmath

[rwst]

It seems in some cases the infinities returned from mpmath need to be changed by the function's evalf() in order to be correct:
Before:

sage: zeta(SR(1))
Infinity
sage: zeta(SR(1.))   <---------
+infinity
sage: type(zeta(SR(1)))
<type 'sage.symbolic.expression.Expression'>
sage: type(zeta(SR(1)).pyobject())
<class 'sage.rings.infinity.UnsignedInfinity'>
sage: type(zeta(SR(1.)))
<type 'sage.symbolic.expression.Expression'>
sage: type(zeta(SR(1.)).pyobject())
<type 'sage.rings.real_mpfr.RealNumber'>

The ticket should result in:

sage: zeta(SR(1))
Infinity
sage: zeta(SR(1.))
Infinity
sage: type(zeta(SR(1)))
<type 'sage.symbolic.expression.Expression'>
sage: type(zeta(SR(1)).pyobject())
<class 'sage.rings.infinity.UnsignedInfinity'>
sage: type(zeta(SR(1.)))
<type 'sage.symbolic.expression.Expression'>
sage: type(zeta(SR(1.)).pyobject())
<class 'sage.rings.infinity.UnsignedInfinity'>

Ideally, fix other such cases too in this ticket.

Depends on #22838

CC: @paulmasson

Component: symbolics

Author: Ralf Stephan

Branch/Commit: 5d2d860

Reviewer: Travis Scrimshaw

Issue created by migration from https://trac.sagemath.org/ticket/19439

[rwst]

comment:1

Polylog uses zeta here, so it's mainly because of RR(1).zeta() not being converted in symbolic/function.pyx or the RR functions not using the InfinityRing elements.

[rwst]

comment:2

The problematic output is rather for the last lines, ie symbolic input, which should produce symbolic output. It does, by wrapping FP infinity into SR. It would be better if that would rather produce the infinity from the ring.

[rwst]

Branch: u/rws/corrections_to_infinities_returned_by_mpmath

[rwst]

New commits:

5d2d860

19439: Corrections to infinities returned by mpmath

[rwst]

Author: Ralf Stephan

[rwst]

Dependencies: pynac-0.7.6

[rwst]

Commit: 5d2d860

[rwst]

Changed dependencies from pynac-0.7.6 to #22838

[tscrim]

Reviewer: Travis Scrimshaw

[tscrim]

comment:12

LGTM.

[vbraun]

Changed branch from u/rws/corrections_to_infinities_returned_by_mpmath to 5d2d860