Assumptions system

[proy87]

How can I assume that x>2?
I need to rewrite Abs(x-2) as x-2 and also make assumption on the variable.

[sylee957]

The only predicate to describe such assumption is Q.is_true, but I don't think that any work is done about that.

>>> from sympy import *

>>> x = Symbol('x', real=True)
>>> refine(Abs(x - 2), assumptions=Q.is_true(x>2))
Abs(x - 2)

[petschge]

I also just got bit by that issue as documented in the now closed #20636.

[oscarbenjamin]

I think that there are other issues corresponding to this with more discussion. Handling inequalities in the assumptions system is definitely high priority but it's not easy.