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
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
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