How to iterate through the list of maps in Elixir?

Question

I can't understand how to iterate with index in Elixir.

For example, I have this snippet from java and I want to translate it into Elixir:

for(int i = 1; i < list.size(); i++) {
   list.order = i;
}

Lets say that list is a list of maps from Elixir. I can't understand how to do this either in Elixir way or just iterate with some index variable.

Answer 1

While the answer by Justin is perfectly valid, the idiomatic Elixir solution would be to use Enum.with_index/2:

list = ~w|a b c d e|
list
|> Enum.with_index()
|> Enum.each(fn {e, idx} -> IO.puts "Elem: #{e}, Idx: #{idx}" end)

#⇒ Elem: a, Idx: 0
#⇒ Elem: b, Idx: 1
#⇒ Elem: c, Idx: 2
#⇒ Elem: d, Idx: 3
#⇒ Elem: e, Idx: 4

Answer 2

When working with a language that doesn't allow mutation of data, it's not so straightforward as iterating over a collection and setting values. Instead, you need to create a new collection with new objects that have your field set.

In Elixir, you can do this with a foldl:

List.foldl(
  list, 
  (1, map), 
  fn(l, (i, map)) -> (i+1, Map.update(map, :some_key, $(i)))
)