Hello, I’d try to simplify it by moving the function to the view module, using string interpolation, i.e. (disclaimer: untested code ahead…)

def eval_item(x, index) do
  case x do
    {k, v} -> 
      "#{k} #{v} : @index: #{index}"
    val ->
      "#{val} : @index: #{index}"
    end
end

or with two functions using pattern matching on arguments (that I prefer as I find it easier to read):

def eval_item({k, v} = x, index), do: "#{k} #{v} : @index: #{index}"

def eval_item(x, index), do: "#{x} : @index: #{index}"

then in the template you could just:

<%= Enum.with_index(list) |> Enum.map(&eval_item/2) %> 

hth.

I would even go further and put all logic in a helper function. Putting logic in the template is not something I would advise.

Somehing like

<%= do_something(list) %> 

yes, good advice!

[…edit…] Putting all together would look like:

in template.html.eex

<%= iterate_over(list) %> 

in template_view.ex

def iterate_over(list) do
 list
 |> Enum.with_index()
 |> Enum.map(&eval_item/2)
end

defp eval_item({k, v} = _x, index), do: "#{k} #{v} : @index: #{index}"

defp eval_item(x, index), do: "#{x} : @index: #{index}"

<% %> doesn’t work like that (been there tried that ), and you can simplify the map/case by pattern matching in the function signatures.

untested:

<%= Enum.with_index(list) |> Enum.map(fn
  {{k, v}, index} ->
    "#{k} #{v}: @index: #{index}"
  {x, index} ->
    "#{x}: @index: #{index}"
end) %>