Re: assigning functions

*To*: mathgroup at smc.vnet.net*Subject*: [mg56250] Re: assigning functions*From*: Peter Pein <petsie at arcor.de>*Date*: Wed, 20 Apr 2005 05:30:59 -0400 (EDT)*References*: <opspforld7yw49cj@juergen> <d42kri$3du$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

juejung wrote: > sorry, i just found the solution myself. yes, the help file is helpful ;-) > > f[x_] := x^2; > fprime[x_] = D[f[x], x] > > works just fine! > the "set delayed assignment rule" for the second part was wrong. > > best > juergen > > On Mon, 18 Apr 2005 10:17:35 -0500, juejung <juejung at indiana.edu> 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] >> >>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 > Just to remind you: In[1]:= f[x_] := x^2; fprime[x_] = D[f[x], x]; fprime[z] f[x_] := x^3; fprime[z] Out[3]= 2*z Out[5]= 2*z fprime didn't recognize the change of f. f[x_] := x^2; fprimeDelayed[x_] := Derivative[1][f][x] fprimeDelayed[z] f[x_] := x^3; fprimeDelayed[z] Out[8]= 2*z Out[10]= 3*z^2 this one did. -- Peter Pein Berlin