Peter Otten wrote: > Alan aka David Isaac wrote: > > >>> #evaluate polynomial (coefs) at x using Horner's rule > >>> def horner(coefs,x): return reduce(lambda a1,a2: a1*x+a2,coefs) > > > It just cannot get simpler or more expressive. > > But is it correct? > > >>> a0, a1, a2 = 1, 2, 3 > >>> x = 2 > >>> a0 + x*(a1 + x*(a2)) > 17 > >>> def horner(coefs, x): return reduce(lambda a1, a2: a1*x + a2, coefs) > ... > >>> horner([a0, a1, a2], x) > 11 > > Are we merely employing different conventions for the order of coefficients > or is that simple and expressive lambda/reduce stuff obscuring an error? > I think horner needs the coefs be "reversed", comparing with how we like to express polynomial in general, that is how I read those math formulas about horner anyway.
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