For the benefit of the O.P., in case of discomfort with using pure
functions here=85 one can use ordinary explicit function definitions as well:
g[fn_] := D[fn, x] + D[fn, y]
g[x + y]
f[x, y] := Sin[x y]
Nest[g, f[x,y], 2]
gi[k_][fn_]:= Nest[g, fn, k]
On the other hand, if one wanted to get fancier, he could provide additional arguments that specify the names of the variables with respect to which the derivatives are taken. I leave this as an exercise.
On Aug 22, 2012, at 5:19 AM, Dr. Wolfgang Hintze <w...@snafu.de> wrote:
> On 22 Aug., 08:24, S16 <sowna...
>> On Saturday, August 18, 2012 8:46:10 AM UTC+1, S16 wrote:
>>> I am very new to Mathematica, so need a bit of help!
>>> I want to define a function (called say G) that is defined as
>>> G = =E2=88=82/=E2=88=82x - =
Murray Eisenberg =
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