Re: assigning functions

*To*: mathgroup at smc.vnet.net*Subject*: [mg56236] Re: assigning functions*From*: dh <dh at metrohm.ch>*Date*: Wed, 20 Apr 2005 05:30:10 -0400 (EDT)*References*: <d42kom$3c8$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Hi juergen, see below: juejung wrote: > dear all, > > i would like to do the following. > assign a function: > f[x_] := x^2; > > take its derivate: > D[f[x], x] > > and assign the result of this to a new function, like fprime[x]: > fprime[x_] := D[f[x], x] ":=" tells Mathematica to delay evaluation of the derivative. If you later use e.g. fprime[2], Mathematica replace x by 2 in your expression giving: D[f[2], 2] what is wrong. What you want is to evaluate the derivative at define-time, d.h.: fprime[x_] = D[f[x], x] Sincerely, Daniel > > unfortunately that doesn't work. > when i try to evaluate fprime[2] i get an error message. > > can somebody please help, this haunts me for a while now. > > thanks and all the best > > juergen >