use Pynac for some symbolic comparisons instead of Maxima

[rwst]

This:

sage: bool(exp(x)>=0)
True

unexpectedly uses Maxima, and gets it wrong, too (the already known complex domain problem, see e.g. #14305).

Since Pynac can now assign info flags to function expressions the possible cases for abs, factorial, binomial, real, imag, step should be implemented in Pynac (this is pynac/pynac#78) and the cases like above handled in Pynac.

The repercussions are not limited to such comparisons. The more expressions have info flags set the more expressions with more complicated structure can be decided and more questions answered.

Depends on #22219

Component: symbolics

Author: Ralf Stephan

Branch/Commit: u/rws/use_pynac_for_some_symbolic_comparisons_instead_of_maxima @ 18c2768

Issue created by migration from https://trac.sagemath.org/ticket/18883

[rwst]

comment:1

Turns out that, additionally, an explicit nonzero info flag is needed in Pynac because without a nonzero flag the above test in the reals is always delegated to Maxima, as well. pynac/pynac#79

EDIT: remove nonsense

[rwst]

Branch: pynac-0.4.3

[rwst]

Upstream: Fixed upstream, in a later stable release.

[fchapoton]

comment:4

pynac-0.4.3 is not a git branch

[fchapoton]

Changed branch from pynac-0.4.3 to none

[rwst]

comment:5

This was NOT fixed as claimed in the ticket field.

[rwst]

Changed upstream from Fixed upstream, in a later stable release. to Reported upstream. Developers acknowledge bug.

[rwst]

Branch: u/rws/use_pynac_for_some_symbolic_comparisons_instead_of_maxima

[rwst]

Commit: 5abe68e

[rwst]

comment:7

This commit enables all Pynac relational logic improvements and only falls back on Maxima if Pynac returns Not Implemented.

---

New commits:

5abe68e

18883: take advantage of more fine-grained logic results from Pynac

[rwst]

Dependencies: pynac-0.7.4

[rwst]

comment:8

To fix the Maxima-related problem, as a solution to the complex/real domain issue is not expected it might be possible to use only Pynac with relations, and use both with equality questions.

[rwst]

comment:9

If Pynac should take over all questions on relations then it must be able to also answer this:

            sage: (x > 2).assume()
            sage: bool(x > 0)
            True

because it's impossible do separate domain-only questions from more general ones. That means the workaround mentioned in comment:8 depends on pynac/pynac#227

[sagetrac-git]

Changed commit from 5abe68e to 18c2768

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

18c2768

18883: depend on Pynac handling all inequalities

[rwst]

Changed upstream from Reported upstream. Developers acknowledge bug. to none

[rwst]

Changed dependencies from pynac-0.7.4 to #22219

[rwst]

Author: Ralf Stephan

[rwst]

comment:14

Lots of doctest errors. Back to the drawing board.