Re: Defining differential operators question

*To*: mathgroup at smc.vnet.net*Subject*: [mg13825] Re: Defining differential operators question*From*: Paul Abbott <paul at physics.uwa.edu.au>*Date*: Sat, 29 Aug 1998 04:41:05 -0400*Organization*: University of Western Australia*References*: <6s5lh8$c91@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

tgoetze at my-dejanews.com wrote: > I would like to be able to define a family of differential operators > that act on a function being passed in. For simplicity sake, I will > assume that the functions being passed in are functions of one > variable. > > Suppose that given a list L={a0,a1,a2,a3}, that the differential > operator defined by L, acts on a function F by: > > a0*F + a1*F' + a2*F'' + a3*F''' Here is one solution using MapIndexed: In[1]:= NewD[l_List,f_]:=Function[x,Evaluate[ Plus@@MapIndexed[#1 Derivative[First[#2]-1][f][x]&,l]]] In[2]:= g[x_] := x^3 In[3]:= NewD[{a0,a1,a2,a3},g] Out[3]= 3 2 Function[x$, a0 x$ + 3 a1 x$ + 6 a2 x$ + 6 a3] In[4]:= %[1] Out[4]= a0 + 3 a1 + 6 a2 + 6 a3 Cheers, Paul ____________________________________________________________________ Paul Abbott Phone: +61-8-9380-2734 Department of Physics Fax: +61-8-9380-1014 The University of Western Australia Nedlands WA 6907 mailto:paul at physics.uwa.edu.au AUSTRALIA http://www.physics.uwa.edu.au/~paul God IS a weakly left-handed dice player ____________________________________________________________________