ASKSAGE: Sage Q&A Forum - RSS feedhttps://ask.sagemath.org/questions/Q&A Forum for SageenCopyright Sage, 2010. Some rights reserved under creative commons license.Tue, 03 Nov 2015 22:51:24 +0100What guarantees simplify()?https://ask.sagemath.org/question/30440/what-guarantees-simplify/ How to convert (n!/k!)*binomial(k,n-k) to factorials? From an answer of tmonteil in question 30394:
var('k,n')
expr = n.factorial()/k.factorial()*binomial(k,n-k)
expr.factorial_simplify()
factorial(n)/(factorial(2*k - n)*factorial(-k + n))
The new question is: what is the contract of simplify()
(or factorial_simplify())?
I think a simplification is only useful if it returns
an equivalent expression. Is this is guaranteed?
In our example: Take n=1 and k=0. expr is 0 in this case
but expr.factorial_simplify() is not defined (or gives an
ValueError if executed) because factorial(2*k-n) = factorial(-1).
So my question might be rephrased: Is this an accidental
bug or a systematic unreliability which renders simplify()
essentially useless?
Peter
Peter LuschnyTue, 03 Nov 2015 22:51:24 +0100https://ask.sagemath.org/question/30440/Reliability of Sage vs commercial softwarehttps://ask.sagemath.org/question/8583/reliability-of-sage-vs-commercial-software/Hello everybody,
for future calculations I need a CAS. Up to now, I worked with a free mathematica student licence. But now I need a officially bought version (which I can't afford). I'm now trying to work with Sage but my head of department is no fan of open source projects and thinks, among other things, that it is probably buggy and not as powerful as said mathematica. Could you please tell me how "stable" and "correct" the sage calculations are and give me further information on this topic (I already searched the forum for some information) so that I can present him/them why we should use Sage and nothing like mathematica/mathlab/...
Please tell me if you need more information or clarification.
Thank you all in advance for your effort.
Danielgod.oneWed, 21 Dec 2011 06:47:22 +0100https://ask.sagemath.org/question/8583/