On Sat, Jan 17, 2009 at 11:31 AM, Robert Bradshaw
<rober...@math.washington.edu> wrote:
>
> On Jan 17, 2009, at 6:54 AM, mabshoff wrote:
>
>> ---------- Forwarded message ----------
>> From: Yann Laigle-Chapuy <SNIP>
>> Date: Sat, Jan 17, 2009 at 4:06 AM
>> Subject: [Sage Bug Report] or not?
>> To: Michael Abshoff < SNIP >
>>
>>
>> Hi,
>> is the following a feature or a bug?
>>
>> sage: 0*log(0)
>> ...
>> ValueError: self must be positive
>>
>> ok, but
>>
>> sage: f=x*log(x)
>> sage: f(0)
>> 0
>
> I would say that's a bug. Probably an overly-naive simplification.
> Also, note
It's a bug, but I think there is not much of a point in even reporting
it to trac, since it is already fixed in the new symbolics.... which
Burcin and I wrote 5 *months* ago, and which still aren't the default
in Sage.
sage: var('x',ns=1)
x
sage: f(x) = x*log(x)
sage: f(0)
...
ValueError: self must be positive
-- William
>
> sage: f = x*log(x)
> sage: f(0)
> 0
> sage: f.subs(x=0)
> ------------------------------------------------------------
> Traceback (most recent call last):
> File "<ipython console>", line 1, in <module>
> File "/Users/robert/sage/current/local/lib/python2.5/site-packages/
> sage/calculus/calculus.py", line 3811, in subs
> return self.substitute(*args, **kwds)
> File "/Users/robert/sage/current/local/lib/python2.5/site-packages/
> sage/calculus/calculus.py", line 3808, in substitute
> return X._recursive_sub(kwds)
> File "/Users/robert/sage/current/local/lib/python2.5/site-packages/
> sage/calculus/calculus.py", line 4857, in _recursive_sub
> new_ops = [SR(op._recursive_sub(kwds)) for op in ops]
> File "/Users/robert/sage/current/local/lib/python2.5/site-packages/
> sage/calculus/calculus.py", line 6275, in _recursive_sub
> return ops[0](ops[1]._recursive_sub(kwds))
> File "/Users/robert/sage/current/local/lib/python2.5/site-packages/
> sage/calculus/calculus.py", line 6600, in __call__
> return getattr(x, self._repr_())(*args)
> File "integer.pyx", line 1560, in sage.rings.integer.Integer.log
> (sage/rings/integer.c:11178)
> ValueError: self must be positive
>
> sage: f(x) = x*log(x)
> sage: f(0)
> ------------------------------------------------------------
> Traceback (most recent call last):
> File "<ipython console>", line 1, in <module>
> File "/Users/robert/sage/current/local/lib/python2.5/site-packages/
> sage/calculus/calculus.py", line 5922, in __call__
> return self._expr.substitute(dct)
> File "/Users/robert/sage/current/local/lib/python2.5/site-packages/
> sage/calculus/calculus.py", line 3808, in substitute
> return X._recursive_sub(kwds)
> File "/Users/robert/sage/current/local/lib/python2.5/site-packages/
> sage/calculus/calculus.py", line 4857, in _recursive_sub
> new_ops = [SR(op._recursive_sub(kwds)) for op in ops]
> File "/Users/robert/sage/current/local/lib/python2.5/site-packages/
> sage/calculus/calculus.py", line 6275, in _recursive_sub
> return ops[0](ops[1]._recursive_sub(kwds))
> File "/Users/robert/sage/current/local/lib/python2.5/site-packages/
> sage/calculus/calculus.py", line 6600, in __call__
> return getattr(x, self._repr_())(*args)
> File "integer.pyx", line 1560, in sage.rings.integer.Integer.log
> (sage/rings/integer.c:11178)
> ValueError: self must be positive
>
>
> >
>
--
William Stein
Associate Professor of Mathematics
University of Washington
http://wstein.org
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