Re: apply(sign,x) == x

[Bill Allombert <Bill.Allombert@math.u-bordeaux.fr>]

On Mon, Nov 19, 2018 at 06:38:35PM +0000, Jacques Gélinas wrote:
> apply(f, A): If A  is  a  polynomial or power series,  apply f on all coefficients.

the coefficients of x are 0 and 1, so
apply(sign,x) = sign(0)*x^0+sign(1)*x == x

> Of course, I would expect sign not to return a polynomial, but -1, 0, or 1 as in
> apply(sign,Vec(x)) == [1,0]

[1,0] is neither -1, 0 or 1 !

Cheers,
Bill.