Hi Matthew,
This does appear to be the case. I've just looked over facts.py and
assumptions.py as well.
Interval._intersection evaluates the comparisons and there is an explicit
comment about not doing comparisons on Symbol classes on line 539
# We can't intersect [0,3] with [x,6] -- we don't know if x>0 or x<0
if not self._is_comparable(other):
return None
That would leave open the question of how best to put such machinery into
the Symbol class.
It's not clear to me, BTW, what distinguishes something that belongs in a
FactKb from something that is denoted with a member function such as
Symbol.is_comparable. I gather that "facts" are static (e.g. "this is a
real") rather than contextual (e.g. "this A \in \Real < B \in \Real") but
doesn't that leave such facts out of the scope of the rules engine? Seems
like there is an opportunity there for a lot more power in the system.
Just reviewing, for example, my analysis text there are a lot of "facts"
that might be useful for proofs or reasoning about expressions. I imagine
that's getting out of scope for Sympy, perhaps?
It seems to me that something could be shoe-horned in, but I'd be afraid of
doing something inadequately generalized.
Thanks
-- Simon
On Wednesday, 14 November 2012 15:01:46 UTC-5, Matthew wrote:
>
> I'm not very knowledgeable on this part of SymPy though. Hopefully I am
> wrong.
>
> On Wed, Nov 14, 2012 at 2:01 PM, Matthew Rocklin
> <[email protected]<javascript:>
> > wrote:
>
>> My understanding is that SymPy is not able to handle information like
>> `assume(A<B)`. This has been on our issues list for a while I think.
>>
>
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