List comprehension is... useful

[ndrean]

I had this pretty (useful) complicated function:

def list_tuples_to_unique_keys(parts) do
  key = parts |> hd() |> elem(0)
  new_keys = Enum.map(1..length(parts), &(key <> "-#{&1}"))

  Enum.zip_reduce([parts, new_keys], [], fn [elt, new_key], acc ->
    [
      elt |> Tuple.delete_at(0) |> Tuple.insert_at(0, new_key)
      | acc
    ]
  end)
  |> Enum.sort()
end

Instead, using a comprehension list does the same job and is easy to understand....Never too late to improve!

def  list_tuples_to_unique_keys_from_comprehension(parts) do
  for {{f, l, m}, i}<- Enum.with_index(parts) do
    {f<>"-"<>Integer.to_string(i+1), l,m} 
  end
end

parts = [
    {
       "files",
       [
         {"content-type", "image/png"},
         {"content-disposition", "form-data; name=\"files\"; filename=\"first.png\""}
       ], 
       %{path: "..", content_type: "image/png", filename: "first.png"}
    },
    {
       "files",
       [
         {"content-type", "image/webp"},
         {"content-disposition", "form-data; name=\"files\"; filename=\"second.webp\""}
       ], 
       %{path: "...", content_type: "image/webp", filename: "second.webp"}
    }
]

list_tuples_to_unique_keys_from_comprehension(parts)
[
  {
     "files-1",
       ^^^
     [
       {"content-type", "image/png"},
       {"content-disposition", "form-data; name=\"files\"; filename=\"first.png\""}
     ], 
     %{filename: "first.png", path: "..", content_type: "image/png"}
  },
  {
     "files-2",
      ^^^
     [
       {"content-type", "image/png"},
       {"content-disposition", "form-data; name=\"files\"; filename=\"first.png\""}
     ], 
     %{filename: "first.png", path: "..", content_type: "image/png"}
  }
]

[ndrean]

https://www.mitchellhanberg.com/the-comprehensive-guide-to-elixirs-for-comprehension/

[ndrean]

Just to add that the "comprehension" version works when you know exactly what you are receiving, whilst the first version works whatever you receive, as long as the "key" is the first element of the tuple of course.

The learning is more about the power of "comprehensions".