Access list position from iterator?

Question

Consider a list, e.g.:

list = {a,b,c,d};

One can compose a Table by directly iterating through the list:

tab = Table[
        (*do something with i*)
      ,{i,list}]

This is useful, since we iterate through all elements in list without introducing an integer counter and notationally cleaner without having to deal with parts list[[...]]. However, sometimes we need to refer back to the position of i in list. Is there a convenient way to know the position of each i within list without calling Position[list,i]? What I mean is, does the iterator store and provide this information as well, so that there is some way to call it directly?

Answer 1

As pointed out by Michael E2 in the comments, a Table function iterator does not make the index available. However, one can use a different function MapIndexed that instead of iterators provides two function arguments #1 and #2 referring to each element and its index respectively as it goes through the list:

tab = MapIndexed[
      (* do something with element `#1` while `#2` stores its position in `list` *)
      &,list]

This is notationally even shorter than the Table. And it generalizes straightforwardly to higher dimensional arrays.