6.7.3 Can you answer these questions?

6.7.3.1 Computations with OptimizedExpressions without completely expanding them

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=221938

I have to manipulate huge expressions that are rational functions of many (30) variables with integer coefficients. Storing them just as a ratio of two polynomials would be impractical. But they can  ... 
[simplifying-expressions] [symbolic] [expression-manipulation] [expression-construction]
 

asked by Vladimir Reshetnikov https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=7288 2 votes

6.7.3.2 LeviCivitaTensor contraction indices

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=222179

apparently my computer has problems when I try to perform a calculation with TensorContract. 
 
In particular, with the second answer to my previous question Contracting indices in lists, I want to  ... 
[list-manipulation] [physics] [vector] [tensors]
                                                                                  

                                                                                  
 

asked by FB20 https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=72314 1 vote

6.7.3.3 Using Fold[ or Map[ Better?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=221941

I'm working through MMA Cookbook by Mangano, page 54. He shows Map is a compact form of Fold function. Is using Fold function important? 
 
myMap3[f_, l_] := Fold[Prepend[#1, f[#2]]&, {}, l] 
... 
[list-manipulation] [functional-style]
 

asked by code9910743 https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=59860 2 votes