[Numpy-discussion] Polynomial evaluation inconsistencies
Maxwell Aifer
maifer at haverford.edu
Sat Jun 30 18:05:12 EDT 2018
Oh, clever... yeah I think that would be very cool. But shouldn't it call
the constructor with Polynomial([0,1])?
On Sat, Jun 30, 2018 at 5:41 PM, Eric Wieser <wieser.eric+numpy at gmail.com>
wrote:
> Since the one of the arguments for the decreasing order seems to just be
> textual representation - do we want to tweak the repr to something like
>
> Polynomial(lambda x: 2*x**3 + 3*x**2 + x + 0)
>
> (And add a constructor that calls the lambda with Polynomial(1))
>
> Eric
>
>
> On Sat, 30 Jun 2018 at 14:30 Eric Wieser <wieser.eric+numpy at gmail.com>
> wrote:
>
>> “the intuitive way” is the decreasing powers.
>>
>> An argument against this is that accessing the ith power of x is spelt:
>>
>> - x.coeffs[i] for increasing powers
>> - x.coeffs[-i-1] for decreasing powers
>>
>> The former is far more natural than the latter, and avoids a potential
>> off-by-one error
>>
>> If I ask someone to write down the coefficients of a polynomial I don’t
>> think anyone would start from c[2]
>>
>> You wouldn’t? I’d expect to see
>>
>> [image: f(x) = a_3x^3 + a_2x^2 + a_1x + a_0]
>>
>> rather than
>>
>> [image: f(x) = a_0x^3 + a_1x^2 + a_2x + a_3]
>>
>> Sure, I’d write it starting with the highest power, but I’d still number
>> my coefficients to match the powers.
>>
>>
>> Eric
>>
>>
>
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