I think this is more or less what I meant. When I said, "global assumptions,"
I meant assumptions that you can stick with a symbol throughout a scope, as
opposed to having to manually tack on an Assume object whenever you want to use
those assumptions. But of course they will need to be localized throughout a
scope.
Aaron Meurer
On Apr 1, 2010, at 2:20 PM, Vinzent Steinberg wrote:
> 2010/4/1 Aaron S. Meurer <asmeu...@gmail.com>:
>> I like this idea. Maybe it doesn't necessarily have to be tied to Symbol.
>> If there is some kind of global assumptions table, or you are in some "with
>> Assume(x, Q.something):" context, then x.is_something would just be a
>> shortcut to look it up in there. It may make it seem to the user that the
>> assumptions are stored in the symbol, but it doesn't really matter because
>> that is just an implementation detail that he won't even care about either
>> way, unless he wants to implement some assumptions or a special symbol type
>> of his own.
>>
>
> Global assumptions are a mess, you actually never want them, I think
> they should be removed from sympy. It works only for very simple and
> small scripts, but not for complex stuff. If some part of your code
> uses
>
> x = Symbol('x', positive=True)
>
> and another part
>
> x = Symbol('x', negative=True)
>
> you got a problem. Even if you overwrite the global assumption, it
> does not work if you call a subroutine that changes them and breaks
> the assumptions of the routine calling the subroutine.
>
> Really, you don't want global assumptions, you want local assumptions.
>
> Using Python's introspection, it should be easy to implement
> assumptions that are only valid for the local scope and automatically
> garbage-collected if no longer necessary. It would be maybe somewhat
> hackish, but it is clearly defined behavior.
>
> It would be a solution to clean your global assumptions explicitly,
> but this is not backward-backward compatible and unnecessarily
> cumbersome. And it's a huge amount of useless code added to sympy.
>
> Vinzent
>
> --
> You received this message because you are subscribed to the Google Groups
> "sympy-patches" group.
> To post to this group, send email to sympy-patc...@googlegroups.com.
> To unsubscribe from this group, send email to
> sympy-patches+unsubscr...@googlegroups.com.
> For more options, visit this group at
> http://groups.google.com/group/sympy-patches?hl=en.
>
--
You received this message because you are subscribed to the Google Groups
"sympy-patches" group.
To post to this group, send email to sympy-patc...@googlegroups.com.
To unsubscribe from this group, send email to
sympy-patches+unsubscr...@googlegroups.com.
For more options, visit this group at
http://groups.google.com/group/sympy-patches?hl=en.
