Creating list adding elements on specific conditions?

Questions & Help Questions
1

Often I want to create a list in Elixir that contains certain elements, but only if specific conditions are met for each element or group of elements.

In a language with mutable data, it would be something like

array = [0]

if (cond1) {
  array.push(1)
}
if (cond2) {
  array.push(2)
}
if (cond3) {
  array.push(3)
}

return array

How would you re-write this in Elixir?

Currently I’ve been creating separate lists for each condition and concatenating them in the end:

initial = [0]
list_1 = if cond1 do
  [1]
else
  []
end

list_2 = if cond2 do
  [2]
else
  []
end

list_3 = if cond3 do
  [3]
else
  []
end

Enum.concat(initial, list_1)
|> Enum.concat(list_2)
|> Enum.concat(list_3)

This works but it’s not great, because I have to make sure I return an empty list every time. In some cases where logic in the if-block is complicated, it could lead to a lot of else [] end.

Any ideas how to refactor this to something more concise and/or avoid repetition are appreciated. Thanks!