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Help with a Fold/Outer one-liner

  • To: mathgroup at
  • Subject: [mg28220] Help with a Fold/Outer one-liner
  • From: "Emilio Martin-Serrano Sobrino" <emilio.martin at>
  • Date: Thu, 5 Apr 2001 03:00:33 -0400 (EDT)
  • Sender: owner-wri-mathgroup at

Hi math groupers:

Could anyone give me a hand with this? 

Let {m[1],m[2], m[3],m[4]} be a list of tensors over N^4 . I want to apply
the following function to the previous list: 

With[{vars = {x1,x2,x3,x4}}, Fold[Outer[D, #, vars]&, m1,{m2,m3,m4}]]  (*let
us consider {x1,x2,x3,x4} as the actual dimension names  } *).

In fact the length of the list and the dimensions should not matter, I put
"4" to make things clearer.

And I did this: 

With[{vars =(*Extract de list of the dimensions names to differentiate*)},
Fold[Outer[D, #, vars]&, First[List@@#],Drop[List@@#,1]]]&/@

But it does not work.

My main problem is with how to extract the dimension names (or the length)

Any help?


Emilio Martin-Serrano

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