What would be the best / correct way to implement the following code in Elixir:
foreach( var item in items) {
foreach(var num in get_nums_from(item)) {
yield return is_valid(num) ? num : -1;
} }
Many thanks.
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3 Answers
Another approach, assuming laziness is not a requirement, is a list comprehension:
for item <- items, num <- get_nums_from(item) do
if is_valid?(num), do: num, else: -1
end
Comments
Bitwalker's response answers your question nicely; however, what are you doing with all those -1s? If you're just going to filter them out later, consider something like:
for i <- items, num <- get_nums_from(item), is_valid?(num), do: num
In executable terms that looks like
iex(2)> for i <- [[1,2,3],[4,5,6],[7,8,9]], j <- i, rem(j, 2) == 0, do: j
[2, 4, 6, 8]
Or maybe give a look at Enum.filter/2.
Comments
A free translation of the loop will be something like:
Enum.flat_map(items, fn (item) ->
Enum.map(get_nums_from(item), fn (num) ->
if is_valid?(num), do: num, else: -1
end)
end)
If you also want to preserve the lazy character of the iteration (which I think the .net version will have) you need to use Stream instead, to create a lazy sequence:
Stream.flat_map(items, fn (item) ->
Stream.map(get_nums_from(item), fn (num) ->
if is_valid?(num), do: num, else: -1
end)
end)
