Re: Re: FromDigits[{135,21}] -> 1371 (??!!)
- To: mathgroup at smc.vnet.net
- Subject: [mg53765] Re: [mg53763] Re: FromDigits[{135,21}] -> 1371 (??!!)
- From: Bob Hanlon <hanlonr at cox.net>
- Date: Thu, 27 Jan 2005 05:40:57 -0500 (EST)
- Reply-to: hanlonr at cox.net
- Sender: owner-wri-mathgroup at wolfram.com
FromDigits just implements a polynomial in the specified base. FromDigits[{a1,a2,a3,a4}] 10 (10 (10 a1+a2)+a3)+a4 FromDigits[{a1,a2,a3,a4},b]== Fold[b*#1+#2&,0,{a1,a2,a3,a4}] // ExpandAll True Consequently, FromDigits is almost an inverse function of CoeffiicientList. They use reverse orderings of the coefficients. poly = x^4 + 2*x^3*y + 5*x*y^2 + 13*y^4; poly== FromDigits[Reverse[CoefficientList[poly,x]],x]== FromDigits[Reverse[CoefficientList[poly,y]],y] True Bob Hanlon > > From: "Astanoff" <astanoff at yahoo.fr> To: mathgroup at smc.vnet.net > Date: 2005/01/26 Wed AM 04:37:40 EST > To: mathgroup at smc.vnet.net > Subject: [mg53765] [mg53763] Re: FromDigits[{135,21}] -> 1371 (??!!) > > > Can anyone please explain what happens, > > if "Digits" actually are "integers": > > FromDigits[{3,2}] > > 32(!) > > FromDigits[{13,2}] > > Digit : "One of the ten Arabic number symbols, 0 through 9, > or such a symbol used in a system of numeration". > So, without any base specified, FromDigits[{13,2}] > assumes default base 10 and should output an error message. > Imho, that's a bug. > > v.a. > >