Fix bug: Enum.slice selecting extra element

[sabiwara]

I found one last bug in Enum.slice with stepped ranges on streams, which might be including an extra element:

iex(3)>  1..10 |> Stream.take(10) |> Enum.slice(2..5//2)
[3, 5, 6]
iex(4)>  1..10 |> Enum.take(10) |> Enum.slice(2..5//2)
[3, 5]

[whatyouhide]

Nice, good catch!

[whatyouhide]

My 2c:

Suggested change

	case to_drop do
	1 -> {:halt, {start, amount, to_drop, [entry | list]}}
	_ -> {:halt, {start, amount, to_drop, list}}
	end
	if to_drop == 1 do
	{:halt, {start, amount, to_drop, [entry | list]}}
	else
	{:halt, {start, amount, to_drop, list}}
	end

[sabiwara]

Thank you for the comment. The idea here was to keep consistency with the code just above:

case to_drop do
   1 -> {:cont, {start, amount - 1, step, [entry | list]}}
   _ -> {:cont, {start, amount - 1, to_drop - 1, list}}     
end

Do you think both should be changed? Or is there a performance implication behind the original code?

[josevalim]

Performance is the same. Both snippets are fine, so let’s keep it as is. :)

[josevalim]

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