[Numpy-discussion] Polynomial evaluation inconsistencies

Eric Wieser wieser.eric+numpy at gmail.com
Sat Jun 30 17:41:28 EDT 2018


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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