[Numpy-discussion] Polynomial evaluation inconsistencies (original) (raw)

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: 2x**3 + 3x**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) = a3x^3 + a2x^2 + a1x + a0] rather than [image: f(x) = a0x^3 + a1x^2 + a2x + a3] 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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