Lazy list comprehension in Elixir?

问题:

Is there a way to make list comprehension lazy in Elixir? If not, is there a way to turn this into a Stream?

my_list = for i <- (1..1000000), j <- (1..1000000), do: {i, j}

This code snippet blows my program by taking too much memory.

I want to apply a filter, map and reduce on my_list.

回答1:

A comprehension is a flat map. So your code is equivalent to:

Stream.flat_map 1..1000000, fn i ->
  Stream.flat_map 1..1000000, fn j ->
    [{i, j}]
  end
end

I have proposed a "stream for" and "parallel for" for future Elixir versions, however it is pending some other improvements to the language.