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Problem with access nested list

• To: mathgroup at smc.vnet.net
• Subject: [mg121140] Problem with access nested list
• From: Sam Takoy <sam.takoy at yahoo.com>
• Date: Wed, 31 Aug 2011 06:04:19 -0400 (EDT)
• Delivered-to: l-mathgroup@mail-archive0.wolfram.com

Hi,

Below is a simple code, that constructs the n-dimensional permutation
symbol (http://mathworld.wolfram.com/PermutationSymbol.html). I found
myself jumping through hoops to accomplish a simple task.

The main obstacle was: If I have and n x n x n list "temp", and I want
to access the entry temp[[1, 2, 3]], but the numbers 1 2 and 3 are
available in a list indicies = {1,2,3}, how do I do it? I tried
temp[[list]] but that's not it. What I came up with is essentially

Apply[Part[temp, #]&, indices]

to convert from a list to arguments. I'm sure I'm missing something.

Also, how to avoid the ugly loop?

Many thanks in advance!

Sam

Permutator[n_]  := Module[{temp, perms, i},
   temp = ConstantArray[0, ConstantArray[n, n]];
   setValue[val_][indices__] :=
    Module[{}, Part[temp, indices] = val];

   perms = Permutations[Range[1, n]];
   For[i = 1, i <= Length[perms], i = i + 1,
    setValue[Signature[perms[[i]]]] @@ perms[[i]];
    ];
   temp
   ];

• Follow-Ups:
  • Re: Problem with access nested list
    • From: Heike Gramberg <heike.gramberg@gmail.com>