assumptions and simplifications [Re: Maple bugs are ubiquitous: A bug the long-liver in assuming (2001--2007--?)]

On Jun 21, 1:23 pm, Vladimir Bondarenko <v...@xxxxxxxxxxxxxxx> wrote:
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If the same bugs exist through numerous software releases,
I think that is valuable public information.

It just should not happen.

-- Brad Cooper

As quotes go, this is at best out of context. For a start, it is not
clear whether the author has any perspective on the type of software
in question. I would strongly suspect not.


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Hello again from the VM machine...

.................................................................
BUG # XXXXX assuming: assuming <> assume

REGRESSION: NO

REPRODUCIBLE: ALWAYS
[...]
DESCRIPTION: According to Help, ?assuming

"The expression assuming property calling sequence
evaluates the expression under the assumption
property on all names in expression."

TEST CASE: restart; ln(2*a)-ln(a) assuming a > 0;

ACTUAL: ln(2*a)-ln(a)

EXPECTED: ln(2)

CHECKUP: assume(a > 0): simplify(ln(2*a)-ln(a));

ln(2)

What is the claimed bug? That the test case result did not do a
simplification? That's not a bug unless there is a claim to the effect
that one should have been done, and I see no such wording in the usage
message.

For comparison here is similar Mathematica in/out.

In[40]:= Assuming[a>0, Log[2*a]-Log[a]]

Out[40]= -Log[a] + Log[2 a]

In[42]:= Assuming[a>0, Simplify[Log[2*a]-Log[a]]]

Out[42]= Log[2]

.................................................................

Enjoy:

Maple 11> simplify(
ln(2222222222222222222222222222222222222222222222222222222)
- ln(1111111111111111111111111111111111111111111111111111111)
);

ln(2222222222222222222222222222222222222222222222222222222)-
ln(1111111111111111111111111111111111111111111111111111111)

instead of ln(2).
[...]

Best wishes,

Vladimir Bondarenko
[...]

I'm not sure if that last is claimed as a bug or just an example where
a simplification might be done but is not. Since that would involve
gcds but not factoring, it looks like a fairly unimportant missed
opportunity.


Daniel Lichtblau
Wolfram Research

.

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