On Apr 10, 4:18 am, Carl Witty <[EMAIL PROTECTED]> wrote:
> I like the "raise an exception" behavior, because it would eliminate
> questions asking why form1 and form2 below are different (from this
> sage-support
> threadhttp://groups.google.com/group/sage-support/browse_thread/thread/79d0...).
> (I have seen this exact problem at least twice on sage-support.) What
> do you think?
I guess what i suggest wouldn't solve the plot-issue. However, i think
if one doesn't know whether an inequality holds, or if the inequality
simply makes no sense (such as in the case of an unordered field) then
bool() should neither raise an exception nor return False but return
None. I think it is much simpler to have
if bool(x>0) == True:
bla1
elif bool(x>0)==None:
bla2
else:
bla3
than catching exceptions.
Perhaps it would even make sense to have a new type UnknownBool. This
could be returned if the inequality may be true, whereas None could be
returned if the inequality simply makes no sense. I don't like at all
what happens for complex numbers or finite fields!
Here are some examples.
sage: bool(x>0)
False # i think it should be None, or better UnknownBool or so
sage: assume(x>0)
sage: bool(x>-1)
True # fine
sage: bool(x>ComplexNumber(0,0))
True # ??? The complex field is not ordered. So, the answer "True"
doesn't make sense!
sage: bool(x>GF(2)(0))
False # Again, ">" does not apply. So, to get "False" or "True" isn't
quite correct.
sage: bool(x>ComplexNumber(-1,0))
True # --"--
sage: bool(x>ComplexNumber(-1,1))
False # --"--
Yours
Simon
--~--~---------~--~----~------------~-------~--~----~
To post to this group, send email to sage-devel@googlegroups.com
To unsubscribe from this group, send email to [EMAIL PROTECTED]
For more options, visit this group at http://groups.google.com/group/sage-devel
URLs: http://www.sagemath.org
-~----------~----~----~----~------~----~------~--~---
