Filter map varieties in Elixir

comprehension.exs

for num <- [1, 2, 3], num < 3, do: num * 2

filter_map.exs

[1, 2, 3]
|> Enum.filter(fn num -> num < 3 end)
|> Enum.map(fn num -> num * 2 end)

flatten.exs

Enum.flat_map([1, 2, 3], fn num ->
  if num < 3 do
    [num * 2]
  else
    []
  end
end)

reduce.exs

[1, 2, 3]
|> Enum.reduce([], fn num, acc ->
  if num < 3 do
    [num * 2 | acc]
  else
    acc
  end
end)
|> Enum.reverse()

Nice. I usually write reduce with simple condition like this

[1, 2, 3]
|> Enum.reduce([], fn 
  num, acc when num < 3 -> [num * 2 | acc]
  _num, acc -> acc
end)
|> Enum.reverse()