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Re: Defining function with indexed variables

  • To: mathgroup at smc.vnet.net
  • Subject: [mg99344] Re: Defining function with indexed variables
  • From: Bill Rowe <readnews at sbcglobal.net>
  • Date: Sun, 3 May 2009 05:22:27 -0400 (EDT)

On 5/2/09 at 5:58 AM, phhs80 at gmail.com (Paul Smith) wrote:

>How can one define the function

>f(x1,x2,...,x100) := x1^2 + x2^2 + ... + x100^2

>using superscripts?

It isn't clear to me what you are trying to do here. If I wanted
a function that would compute the sum of squares for an
arbitrary number of arguments I would define it as:

f[x___] := Total[{x}^2]

with this definition I can do

In[10]:= f[3, 4, 5]

Out[10]= 50

In[11]:= f[1, 2]

Out[11]= 5

In[12]:= f[Sequence @@ Range[100]]

Out[12]= 338350

But of course I can get the same result by defining this
function to work on a list. That is

g[x_List]:=Total[x^2]

In[14]:= g[{1, 2}]

Out[14]= 5

In[15]:= g[{3, 4, 5}]

Out[15]= 50

In[16]:= g[Range[100]]

Out[16]= 338350

But neither of these definitions use subscripts. I don't
understand what you mean by "using subscripts" in this case.




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