How hard would this be to implement? Can you suggest the simplest way to
add this to new-assumptions?
On Mon, Nov 5, 2012 at 2:09 PM, Ronan Lamy <ronan.l...@gmail.com> wrote:
> Le 03/11/2012 18:28, Matthew Rocklin a écrit :
>
> I've run into an issue with the new assumptions system. Can anyone see
>> what is going on? Here is an example
>>
>> I've written this logic about triangular matrices into an assumptions
>> handler
>>
>> In [1]: X = MatrixSymbol('X', 3, 3)
>> In [2]: Y = MatrixSymbol('Y', 3, 3)
>> In [3]: ask(Q.lower_triangular(X+Y), Q.lower_triangular(X) &
>> Q.lower_triangular(Y))
>> Out[3]: True
>>
>> I've added the following two lines to known_facts
>>
>> Implies(Q.lower_triangular, Q.triangular),
>> Implies(Q.upper_triangular, Q.triangular),
>>
>> Which makes the following possible
>>
>> In [4]: ask(Q.triangular(X), Q.lower_triangular(X))
>> Out[4]: True
>>
>> However I don't seem to be able to combine the two
>>
>> In [5]: ask(Q.triangular(X+Y), Q.lower_triangular(X) &
>> Q.lower_triangular(Y))
>> <returns None>
>>
>> What could be happening here? Does SymPy support this kind of inference?
>>
>
> No, the new-style assumptions don't support this, only the old ones do
> that kind of thing. The new-style assumptions work by either evaluating the
> predicate or making logical deductions from assumptions operating on the
> same argument, but they can't infer the need for intermediate steps (in
> this case Q.lower_triangular(X+Y)).
>
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