Am 2016-04-04 um 18:02 schrieb Peter Luschny:
> > Sage seems to use the definition from Concrete Mathematics by Graham,
>> Knuth and Patashnik:
>> That gives e.g.
>> sage: binomial(-4, 5)
>> -56
>
> Right. GKP call it "upper negation". If you look at my demo-function
> you will see that this condition is preserved in the suggested extension
> (case 3). The proposal returns a superset of the current values.
>
>> Concrete Mathematics is seen as something
>> of a bible in large parts of computer science, and it's unfortunate to
>> disagree with a basic definition in there.
>
> It /extends/ this definition. As long as k>=0 nothing will change
> compared to the GKP definition. Upper negation will be untouched.
According to the patch proposed in the description of #17123, the behaviour
sage: binomial(-1, -1)
0
would change to
sage: binomial(-1, -1)
1
A change like this would silently induce errors in previously valid user code (I
am not speaking about the library which can be doctested, but user code out
there).
Therefore, I am strictly opposed to a change like that.
Introducing a new name or a new parameter (keeping the _current_ behaviour the
default) is fine.
Clemens
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