Multiple response from loop

Questions / Help
1

Hello everybody,
Someone can explain me this result please?
I have 2 list
x = [“0001”, “0002”]
y = [1,1]

And I loop them like this:

for x1 ← x do
for y1<- y do
IO.inspect x1
IO.inspect y1
end
end

But the result is like this:

“0001”
1
“0001”
1
“0002”
1
“0002”
1

But I want result like this :

“0001”
1
“0002”
1
Thanks! :smiley:

2

Do you mean something like Enum.zip/2?

for {x1, y1} <- Enum.zip(x, y) do
3

I want this result after loop:
“0001”
1
“0002”
1

but I receive:
“0001”
1
“0001”
1
“0002”
1
“0002”
1

the result is multiply by 2 , but I want also one result

4

Thanks, it’s resolve my problem

5

If Enum.zip/2 solves your problem then consider using [head | tail] notation for lists like:

defmodule Example do
  # when done or empty input do nothing returning empty list
  def sample([], []), do: []

  # optional code in case you have more items in one of the list
  # def sample([], _non_empty_list), do: []
  # def sample(_non_empty_list, []), do: []

  # loop using [head | tail] notation together with your code
  def sample([head1 | tail1], [head2 | tail2]) do
    IO.puts(head1)
    IO.puts(head2)
    sample(tail1, tail2)
  end
end

x = ["0001", "0002"]
y = [1, 1]
Example.sample(x, y)

This gave you exactly same result, but … Enum.zip is one loop and for is another one - this means that if you write a bit more code then using just one loop your code would be faster.

2 Likes
6

Indeed, it depends on the actual use case and what we want to return.

We might also want to reach for Enum.zip_reduce/4 (for an arbitrary accumulator) or Enum.zip_with/3 (if we want to return a list).

Enum.zip_reduce(x, y, :ok, fn x1, y1, _acc ->
  IO.puts(x1)
  IO.puts(y1)
end)
1 Like