Create an assuming() context manager

[EmmanuelCharpentier]

Inspiration : Ralf Stephan in #22322. Thanks to him for nudging me in the right direction.

Goal : create a tool allowing to create reusable, stackable, assumption elements, thus allowing to get the functionality of Mathematica's Assuming[...,???]

What I mean :

sage: solve(x^2==4, x)
[x == -2, x == 2]
sage: with assuming(x>0): solve(x^2==4, x)
[x == 2]
sage: assumptions()
[]

CC: @rwst

Component: symbolics

Author: Emmanuel Charpentier

Branch/Commit: 017f67c

Reviewer: Ralf Stephan

Issue created by migration from https://trac.sagemath.org/ticket/24119

[EmmanuelCharpentier]

Branch: u/charpent/create_an_assuming___context_manager

[EmmanuelCharpentier]

Commit: 4b5f2ea

[EmmanuelCharpentier]

Author: Emmanuel Charpentier

[EmmanuelCharpentier]

comment:2

Initial proposition.

On 8.1beta9 + #24026+ #24006 + #23990 + #23923 + #24088 + #10035, passes ptestlong with no error whatsoever (1 timeout once on sage -t --long src/sage/modular/hecke/submodule.py, unreproductible).

==>needs_review

[EmmanuelCharpentier]

comment:3

Aaarghh... I've found a subtle bug: after with assuming(): do_something(), the original assumption database is destroyed.

That's due to the fact that forget() is equivalent to forget(assumptions()), i. e. forgets all facts in the database. Hoisted by a "lazy" facility...

I'll fix that (and add a couple doctests for exceptions.

Should we reconsider forget() <==> forget(assumptions()) ?

[sagetrac-git]

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

c50defe

24119 : Debugging, better doctests, a couple of typos

[sagetrac-git]

Changed commit from 4b5f2ea to c50defe

[EmmanuelCharpentier]

comment:5

Replying to @sagetrac-git:

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

c50defe

24119 : Debugging, better doctests, a couple of typos

Passes ptestlong with no errors whatsoever, an one non-reproducible timeout on sage -t --long src/sage/symbolic/expression.pyx.

==>needs_review again.