[R] Indexes for Simplexes

[John Tillinghast]

I'm going to be manipulating some 3-rd and 4-th rank tensors in  
relatively high dimensions, and it would help a great deal to use only  
the unique entries instead of repeating every operation 6 or 24 times.
Operations are tensor-matrix, tensor-vector, and tensor-tensor  
multiplication.
Does anyone have some code where they've done this? I know it will  
take me days to work out all the kinks otherwise.

Thanks
John