calculating with vectors of variable length

*To*: mathgroup at smc.vnet.net*Subject*: [mg124585] calculating with vectors of variable length*From*: Benjamin Hell <hell at exoneon.de>*Date*: Wed, 25 Jan 2012 07:08:44 -0500 (EST)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com

Hi, I'd like to work with vectors of variable length. A short example would be this: a = {a1,...,an} f[x_]:=a.x The vector x should be treated as a vector {x1,...,xn} and n should be variable and not be specified prior to any calculations. One possible calculation would be: D[f,x3] which should give a3 according to the definition of f above. How can I implement that in mathematica? Thanks in advance, Benjamin

**Follow-Ups**:**Re: calculating with vectors of variable length***From:*Ulrich Arndt <ulrich.arndt@data2knowledge.de>